The document discusses immune responses to different types of microbes. It describes how innate and adaptive immunity defend against extracellular bacteria through complement activation, phagocytosis, and antibody production. Intracellular bacteria are targeted by natural killer cells, phagocytes, and T cell-mediated recruitment and activation of phagocytes. Fungi are sensed by phagocytes through pattern recognition receptors, and neutrophils and macrophages play a key role in innate immunity against fungi. The document also outlines strategies used by different microbes to evade the immune system, such as inhibiting phagolysosome fusion or antigenic variation.
Antibodies, also known as immunoglobulins, are Y-shaped proteins produced by B cells in response to antigens. They are composed of four polypeptide chains - two light chains and two heavy chains arranged in a Y shape. The variable regions at the tips of the Y shape give antibodies their ability to bind to specific antigens. The constant regions allow antibodies to activate different immune functions such as complement activation. There are five major classes of antibodies - IgA, IgD, IgE, IgG, and IgM - which have different structures and roles in the immune response.
Adaptive immunity is induced in response to specific antigens after collaboration between phagocytic cells, T and B lymphocytes, and production of immunoglobulins and lymphokines. There are two types of adaptive immunity: humoral immunity mediated by secreted antibodies and cell-mediated immunity which activates phagocytes, natural killer cells, cytotoxic T-lymphocytes and cytokines without antibodies. Humoral immunity involves B cell transformation into plasma cells secreting antibodies, while cell-mediated immunity blocks intracellular microbes by activating macrophages or cytotoxic T cells killing infected cells.
The immune response is how our body recognizes and defends itself against pathogens like bacteria, viruses, and substances that appear foreign and harmful.
This document provides an overview of the immune system and immunity. It defines key terms and outlines the history of immunology. It describes the two main types of immunity - innate and adaptive immunity - and compares their attributes. Innate immunity provides immediate response using physical and chemical barriers, while adaptive immunity has antigen-specific memory cells that mount faster responses. The details of innate immunity mechanisms like phagocytosis and complement system are explained. Adaptive immunity involves both cellular and humoral response mediated by T and B cells.
Cell-mediated immunity is an immune response that does not involve antibodies but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. It is an immune response that does not involve antibodies, but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.
This document summarizes immunity to microbes, including both innate and adaptive immunity. It discusses extracellular bacteria that can replicate outside of cells, such as Staphylococcus aureus and Streptococcus pneumoniae, and the innate immune response of complement activation and phagocytosis. Intracellular bacteria like Mycobacterium tuberculosis that can survive inside cells require a cell-mediated adaptive immune response. The document also covers topics like adaptive humoral and cellular immunity, superantigen activation of T cells, mechanisms of bacterial evasion of the immune system, and the roles of macrophages and cytokines in responses to intracellular microbes.
This document provides an overview of Tajuddin's presentation on adaptive immunity. It discusses the cells and organs involved in adaptive immunity, including B cells and T cells that mature in the bone marrow and thymus respectively. It describes humoral and cell-mediated immunity and the roles of antibodies and T cells. Key topics covered include antigen receptors, cytokines, active and passive immunity, immunoglobulin classes, complement activation, and the differences between T-dependent and T-independent antigens.
The document discusses adaptive immunity and the specific immune response. It describes how adaptive immunity provides lifelong protective immunity through antigen-specific responses that are mediated by lymphocytes, including B cells, T cells, helper T cells, and killer T cells. Lymphocytes have antigen receptors like the B cell receptor and T cell receptor that provide specificity. The adaptive immune response develops over a person's lifetime through somatic recombination and clonal selection that generates a diverse repertoire of lymphocytes each with a unique receptor.
Antibodies, also known as immunoglobulins, are Y-shaped proteins produced by B cells in response to antigens. They are composed of four polypeptide chains - two light chains and two heavy chains arranged in a Y shape. The variable regions at the tips of the Y shape give antibodies their ability to bind to specific antigens. The constant regions allow antibodies to activate different immune functions such as complement activation. There are five major classes of antibodies - IgA, IgD, IgE, IgG, and IgM - which have different structures and roles in the immune response.
Adaptive immunity is induced in response to specific antigens after collaboration between phagocytic cells, T and B lymphocytes, and production of immunoglobulins and lymphokines. There are two types of adaptive immunity: humoral immunity mediated by secreted antibodies and cell-mediated immunity which activates phagocytes, natural killer cells, cytotoxic T-lymphocytes and cytokines without antibodies. Humoral immunity involves B cell transformation into plasma cells secreting antibodies, while cell-mediated immunity blocks intracellular microbes by activating macrophages or cytotoxic T cells killing infected cells.
The immune response is how our body recognizes and defends itself against pathogens like bacteria, viruses, and substances that appear foreign and harmful.
This document provides an overview of the immune system and immunity. It defines key terms and outlines the history of immunology. It describes the two main types of immunity - innate and adaptive immunity - and compares their attributes. Innate immunity provides immediate response using physical and chemical barriers, while adaptive immunity has antigen-specific memory cells that mount faster responses. The details of innate immunity mechanisms like phagocytosis and complement system are explained. Adaptive immunity involves both cellular and humoral response mediated by T and B cells.
Cell-mediated immunity is an immune response that does not involve antibodies but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. It is an immune response that does not involve antibodies, but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.
This document summarizes immunity to microbes, including both innate and adaptive immunity. It discusses extracellular bacteria that can replicate outside of cells, such as Staphylococcus aureus and Streptococcus pneumoniae, and the innate immune response of complement activation and phagocytosis. Intracellular bacteria like Mycobacterium tuberculosis that can survive inside cells require a cell-mediated adaptive immune response. The document also covers topics like adaptive humoral and cellular immunity, superantigen activation of T cells, mechanisms of bacterial evasion of the immune system, and the roles of macrophages and cytokines in responses to intracellular microbes.
This document provides an overview of Tajuddin's presentation on adaptive immunity. It discusses the cells and organs involved in adaptive immunity, including B cells and T cells that mature in the bone marrow and thymus respectively. It describes humoral and cell-mediated immunity and the roles of antibodies and T cells. Key topics covered include antigen receptors, cytokines, active and passive immunity, immunoglobulin classes, complement activation, and the differences between T-dependent and T-independent antigens.
The document discusses adaptive immunity and the specific immune response. It describes how adaptive immunity provides lifelong protective immunity through antigen-specific responses that are mediated by lymphocytes, including B cells, T cells, helper T cells, and killer T cells. Lymphocytes have antigen receptors like the B cell receptor and T cell receptor that provide specificity. The adaptive immune response develops over a person's lifetime through somatic recombination and clonal selection that generates a diverse repertoire of lymphocytes each with a unique receptor.
Complement system and innate immunity - classical & alternative pathways neeru02
The complement system is part of the innate immune system that enhances the ability of antibodies and phagocytes to clear pathogens. It consists of around 20 proteins that are activated via three pathways: the classical pathway activated by antigen-antibody complexes, the lectin pathway activated by lectins binding to pathogens, and the alternative pathway which is continuously active at low levels. Complement activation leads to the formation of the membrane attack complex that forms pores in pathogen cell membranes to kill them directly or mark them for phagocytosis.
T-cells are a type of white blood cell that play a major role in the immune system by fighting infection. There are different types of T-cells that act in various ways to identify and destroy pathogens. T-cells mature and develop in the thymus gland, where they are selected and educated to recognize the body's own cells and mount immune responses against foreign threats. T-cells recognize antigens presented on other cells through molecules of the major histocompatibility complex and are activated through a process that involves antigen presentation, costimulatory signals, and cytokine communication.
The study in immunology provides the fundamental understanding of how the human body defend itself against foreign organisms, materials or particles that have the ability to cause harm to host tissues.
Lect 2 cells of immune system rmc 2016Hassan Ahmad
The document summarizes key aspects of cells of the immune system:
1. Hematopoietic stem cells in the bone marrow give rise to two main immune cell lineages - the lymphoid lineage which includes T cells, B cells, and NK cells, and the myeloid lineage which includes macrophages, dendritic cells, and granulocytes.
2. T cells develop and mature in the thymus, undergoing positive and negative selection to eliminate self-reactive cells. Mature T cells express either CD4 or CD8 and have a specific T cell receptor.
3. B cells develop and mature in the bone marrow, also undergoing selection to eliminate self-reactive cells.
Presentation is good for MBBS (undergraduate) class. Complement system includes normal serum proteins that augment the function of immune system. There are three possible paths through which complement system can proceed. then common path follows leading to the formation of MAC complex that causes bacterial cell lysis. Opsonisation, Viral neutralization, clearing of immune complexes, etc. are other functions of complement system. Important diseases are linked to abnormal regulation of immune system.
1. Dendritic cell eats bugs and displays antigens to naïve T cells using MHC class II. T cells mature.
2. Neutrophil eats and kills bugs with toxic chemicals. NK cell kills infected cells.
3. Helper T cell tells macrophage to eat bugs and tells B cell to make antibodies. Cytotoxic T cell finds and kills infected cells that display antigens using MHC class I.
4. B cell makes antibodies that coat bugs to neutralize and opsonize them, making them targets for macrophages.
This document provides an introduction to immunology. It defines immunology as the study of the immune system and its functions in health and disease. The immune system recognizes, attacks, and remembers pathogens that enter the body using innate and adaptive defenses. Key events in immunology history are described, such as Edward Jenner's discovery of vaccination and the eradication of smallpox. Components of the immune system like antibodies, lymphocytes, and the complement system are introduced. The document also distinguishes between innate immunity, which provides non-specific defenses, and adaptive immunity, which has memory and specificity.
This document discusses several key cells of the innate immune system, including their origins, surface markers, functions, and mechanisms of action. It describes natural killer (NK) cells, which spontaneously kill virus-infected and tumor cells. It also outlines macrophages and their roles in phagocytosis, antigen presentation, and cytokine secretion. Dendritic cells are discussed as the most efficient antigen presenting cells that activate naive T cells. The functions of neutrophils and basophils are also summarized.
This document summarizes innate immunity. It discusses how innate immunity provides a first line of defense through mechanisms that are always active and non-specific, such as physical barriers and cellular responses. Components of innate immunity include epithelial barriers, phagocytes, natural killer cells, the complement system, and inflammatory cytokines. These components work together to recognize microbes, initiate inflammation, opsonize pathogens, and eliminate infections before they can become established.
This document provides an overview of immunology and the immune system. It discusses the types of immunity, including innate and adaptive immunity. It describes the lymphoid organs such as the thymus and bone marrow that are involved in immune cell development. The major cells of the immune system are described, including mononuclear phagocytes, lymphocytes, and their B cell and T cell subsets. Both humoral and cellular immune responses are summarized. Key terms related to immunology and the immune system are also defined.
T cells are activated through the recognition of antigen peptides presented on MHC complexes on antigen presenting cells (APCs). This leads to T cell proliferation and differentiation into effector T cells. Cytotoxic T cells recognize endogenous antigens on MHC I to kill infected cells, while helper T cells recognize exogenous peptides on MHC II and secrete cytokines to stimulate macrophage activation or B cell antibody production. Full T cell activation requires both antigen recognition by the TCR and co-stimulatory signaling between molecules such as B7 and CD28.
Immunity to bacteria and related organisms in animalPakawadee Tie
The document discusses various aspects of acquired immunity to bacteria, viruses, protozoa, and helminths. It describes the mechanisms of both innate and adaptive immunity. For bacteria, the key immune responses are neutralization of toxins, killing bacteria through antibodies and complement, and opsonization leading to phagocytosis. Viruses can evade the immune response through antigenic variation and by inhibiting interferons and antibodies. Immunity to protozoa and helminths involves both humoral and cell-mediated responses, though parasites have developed mechanisms to avoid these defenses.
The document discusses the immune system's mechanisms for fighting different types of microbes:
- Innate and adaptive immunity work together to fight extracellular bacteria through complement activation, phagocytosis, inflammation, antibodies, and CD4+ T cell activation. Intracellular bacteria are targeted through phagocyte, NK cell, and CD4+/CD8+ T cell activation. Viruses are combated via complement, NK cells, type 1 interferons, antibodies, and CD8+ T cells.
- The immune system responds specially to different microbes, though microbes can evade responses. Persistent infections occur when the immune system controls but does not eliminate microbes.
- Recent research includes culturing SARS-CoV-2,
Les mécanismes de la réponse immunitaire innée - Présentation de la 2e édition du Cours international « Atelier Paludisme » - CHIM Pheaktra - INSTITUT PASTEUR de CAMBODGE 5, Bd MONIVONG, BP 983, Phnom Penh, Royaume du Cambodge - Technicien - pheaktra@pasteur-kh.org
This document provides an overview of immunology and some key figures in its history. It begins by explaining that immunology started as a branch of microbiology focused on the study of disease and the immune system's response to antigens. The document then defines immunology as the study of the immune system, which protects the body from infection. It describes the roles of immunologists as scientists who research the immune system in laboratories and clinics. Several pioneering researchers are highlighted, including Anton van Leeuwenhoek, considered the "Father of Microbiology", for his early microscopic observations. Edward Jenner developed the smallpox vaccine in the late 18th century. Later figures like Louis Pasteur, Paul Ehrlich, and Robert Koch made
This document provides an overview of the cells of the immune response. It describes the origin of immune cells from stem cells in the bone marrow and thymus. The main cells discussed are lymphocytes, including T cells which develop in the thymus and have T cell receptors, and B cells which develop in the bone marrow and have antibody receptors. The roles and subsets of T cells such as helper T cells, cytotoxic T cells, regulatory T cells, and memory T cells are summarized. The maturation and antigen-dependent selection of B cells into plasma cells that secrete antibodies is also outlined.
Types of organs system.
∆Primary organs
Immature lymphocytes generated in hematopoiesis mature and become committed to a particular antigenic specificity within the primary lymphoid organs
Only after a lymphocytes has matured within a primary lymphoid organ is the cell immunocompetent (capable of mounting an immune response).
T cells arise in the thymus, and in many mammals—humans
-Bone marrow -supports self-renewal and differentiation of hematopoietic stem cells (HSCs) into mature blood cells.
bone marrow is the site of B-cell origin and development
the long bones (femur, humerus), hip bones (ileum), and sternum tend to be the most active
contains several cell types that coordinate HSC development.
-Thymus
∆secondary organs
Lymph nodes and the spleen are the most highly organized of the secondary lymphoid organs and are compartmentalized from the rest of the body by a fibrous capsule.
lymphoid tissue is organized into structures called lymphoid follicles,
Until it is activated by antigen, a lymphoid follicle—called a primary follicle—comprises a network of follicular dendritic cells and small resting B cells.
After an antigenic challenge, a primary follicle becomes a larger secondary follicle—a ring of concentrically packed B lymphocytes surrounding a center (the germinal center)
-Spleen
-Lymph nodes
-Associated tissue
-MALT
-GALT
-BALT
-CALT
Dr. Alok Tripathi studies immunology at the Department of Biotechnology. The document discusses the history and key concepts of immunology, including:
1. The dual immune system of vertebrates, consisting of cell-mediated and humoral immunity.
2. Early theories on immunity proposed by scientists like Metchnikoff, von Behring, and Paul Ehrlich to explain concepts like phagocytosis, humoral immunity, and the generation of antibody diversity.
3. The development of the clonal selection theory by Burnet, Jerne, and others to explain how the immune system achieves antigen specificity through clonal expansion and memory cells.
The document summarizes the immune system's defenses against various pathogens. It describes both innate and acquired immunity. The innate immune system provides non-specific defenses like physical barriers, chemicals, and phagocytosis. The acquired immune system mounts pathogen-specific responses through antibodies, B cells, T cells, and cytokines. Together these defenses protect the body from bacteria, viruses, and parasites through mechanisms like inflammation, phagocytosis, and cell-mediated or antibody-mediated immunity.
18. Immune Responses to Infectious diseases.pdfbriankash1
Our body's immunity has different means of showing response to pathogens be it virus, bacteria, fungi or parasite by involving the functions of innate and adapted immunity. Some of these pathogens have adopoted means to evade host's immunity system making them survive and cause diseases.
Complement system and innate immunity - classical & alternative pathways neeru02
The complement system is part of the innate immune system that enhances the ability of antibodies and phagocytes to clear pathogens. It consists of around 20 proteins that are activated via three pathways: the classical pathway activated by antigen-antibody complexes, the lectin pathway activated by lectins binding to pathogens, and the alternative pathway which is continuously active at low levels. Complement activation leads to the formation of the membrane attack complex that forms pores in pathogen cell membranes to kill them directly or mark them for phagocytosis.
T-cells are a type of white blood cell that play a major role in the immune system by fighting infection. There are different types of T-cells that act in various ways to identify and destroy pathogens. T-cells mature and develop in the thymus gland, where they are selected and educated to recognize the body's own cells and mount immune responses against foreign threats. T-cells recognize antigens presented on other cells through molecules of the major histocompatibility complex and are activated through a process that involves antigen presentation, costimulatory signals, and cytokine communication.
The study in immunology provides the fundamental understanding of how the human body defend itself against foreign organisms, materials or particles that have the ability to cause harm to host tissues.
Lect 2 cells of immune system rmc 2016Hassan Ahmad
The document summarizes key aspects of cells of the immune system:
1. Hematopoietic stem cells in the bone marrow give rise to two main immune cell lineages - the lymphoid lineage which includes T cells, B cells, and NK cells, and the myeloid lineage which includes macrophages, dendritic cells, and granulocytes.
2. T cells develop and mature in the thymus, undergoing positive and negative selection to eliminate self-reactive cells. Mature T cells express either CD4 or CD8 and have a specific T cell receptor.
3. B cells develop and mature in the bone marrow, also undergoing selection to eliminate self-reactive cells.
Presentation is good for MBBS (undergraduate) class. Complement system includes normal serum proteins that augment the function of immune system. There are three possible paths through which complement system can proceed. then common path follows leading to the formation of MAC complex that causes bacterial cell lysis. Opsonisation, Viral neutralization, clearing of immune complexes, etc. are other functions of complement system. Important diseases are linked to abnormal regulation of immune system.
1. Dendritic cell eats bugs and displays antigens to naïve T cells using MHC class II. T cells mature.
2. Neutrophil eats and kills bugs with toxic chemicals. NK cell kills infected cells.
3. Helper T cell tells macrophage to eat bugs and tells B cell to make antibodies. Cytotoxic T cell finds and kills infected cells that display antigens using MHC class I.
4. B cell makes antibodies that coat bugs to neutralize and opsonize them, making them targets for macrophages.
This document provides an introduction to immunology. It defines immunology as the study of the immune system and its functions in health and disease. The immune system recognizes, attacks, and remembers pathogens that enter the body using innate and adaptive defenses. Key events in immunology history are described, such as Edward Jenner's discovery of vaccination and the eradication of smallpox. Components of the immune system like antibodies, lymphocytes, and the complement system are introduced. The document also distinguishes between innate immunity, which provides non-specific defenses, and adaptive immunity, which has memory and specificity.
This document discusses several key cells of the innate immune system, including their origins, surface markers, functions, and mechanisms of action. It describes natural killer (NK) cells, which spontaneously kill virus-infected and tumor cells. It also outlines macrophages and their roles in phagocytosis, antigen presentation, and cytokine secretion. Dendritic cells are discussed as the most efficient antigen presenting cells that activate naive T cells. The functions of neutrophils and basophils are also summarized.
This document summarizes innate immunity. It discusses how innate immunity provides a first line of defense through mechanisms that are always active and non-specific, such as physical barriers and cellular responses. Components of innate immunity include epithelial barriers, phagocytes, natural killer cells, the complement system, and inflammatory cytokines. These components work together to recognize microbes, initiate inflammation, opsonize pathogens, and eliminate infections before they can become established.
This document provides an overview of immunology and the immune system. It discusses the types of immunity, including innate and adaptive immunity. It describes the lymphoid organs such as the thymus and bone marrow that are involved in immune cell development. The major cells of the immune system are described, including mononuclear phagocytes, lymphocytes, and their B cell and T cell subsets. Both humoral and cellular immune responses are summarized. Key terms related to immunology and the immune system are also defined.
T cells are activated through the recognition of antigen peptides presented on MHC complexes on antigen presenting cells (APCs). This leads to T cell proliferation and differentiation into effector T cells. Cytotoxic T cells recognize endogenous antigens on MHC I to kill infected cells, while helper T cells recognize exogenous peptides on MHC II and secrete cytokines to stimulate macrophage activation or B cell antibody production. Full T cell activation requires both antigen recognition by the TCR and co-stimulatory signaling between molecules such as B7 and CD28.
Immunity to bacteria and related organisms in animalPakawadee Tie
The document discusses various aspects of acquired immunity to bacteria, viruses, protozoa, and helminths. It describes the mechanisms of both innate and adaptive immunity. For bacteria, the key immune responses are neutralization of toxins, killing bacteria through antibodies and complement, and opsonization leading to phagocytosis. Viruses can evade the immune response through antigenic variation and by inhibiting interferons and antibodies. Immunity to protozoa and helminths involves both humoral and cell-mediated responses, though parasites have developed mechanisms to avoid these defenses.
The document discusses the immune system's mechanisms for fighting different types of microbes:
- Innate and adaptive immunity work together to fight extracellular bacteria through complement activation, phagocytosis, inflammation, antibodies, and CD4+ T cell activation. Intracellular bacteria are targeted through phagocyte, NK cell, and CD4+/CD8+ T cell activation. Viruses are combated via complement, NK cells, type 1 interferons, antibodies, and CD8+ T cells.
- The immune system responds specially to different microbes, though microbes can evade responses. Persistent infections occur when the immune system controls but does not eliminate microbes.
- Recent research includes culturing SARS-CoV-2,
Les mécanismes de la réponse immunitaire innée - Présentation de la 2e édition du Cours international « Atelier Paludisme » - CHIM Pheaktra - INSTITUT PASTEUR de CAMBODGE 5, Bd MONIVONG, BP 983, Phnom Penh, Royaume du Cambodge - Technicien - pheaktra@pasteur-kh.org
This document provides an overview of immunology and some key figures in its history. It begins by explaining that immunology started as a branch of microbiology focused on the study of disease and the immune system's response to antigens. The document then defines immunology as the study of the immune system, which protects the body from infection. It describes the roles of immunologists as scientists who research the immune system in laboratories and clinics. Several pioneering researchers are highlighted, including Anton van Leeuwenhoek, considered the "Father of Microbiology", for his early microscopic observations. Edward Jenner developed the smallpox vaccine in the late 18th century. Later figures like Louis Pasteur, Paul Ehrlich, and Robert Koch made
This document provides an overview of the cells of the immune response. It describes the origin of immune cells from stem cells in the bone marrow and thymus. The main cells discussed are lymphocytes, including T cells which develop in the thymus and have T cell receptors, and B cells which develop in the bone marrow and have antibody receptors. The roles and subsets of T cells such as helper T cells, cytotoxic T cells, regulatory T cells, and memory T cells are summarized. The maturation and antigen-dependent selection of B cells into plasma cells that secrete antibodies is also outlined.
Types of organs system.
∆Primary organs
Immature lymphocytes generated in hematopoiesis mature and become committed to a particular antigenic specificity within the primary lymphoid organs
Only after a lymphocytes has matured within a primary lymphoid organ is the cell immunocompetent (capable of mounting an immune response).
T cells arise in the thymus, and in many mammals—humans
-Bone marrow -supports self-renewal and differentiation of hematopoietic stem cells (HSCs) into mature blood cells.
bone marrow is the site of B-cell origin and development
the long bones (femur, humerus), hip bones (ileum), and sternum tend to be the most active
contains several cell types that coordinate HSC development.
-Thymus
∆secondary organs
Lymph nodes and the spleen are the most highly organized of the secondary lymphoid organs and are compartmentalized from the rest of the body by a fibrous capsule.
lymphoid tissue is organized into structures called lymphoid follicles,
Until it is activated by antigen, a lymphoid follicle—called a primary follicle—comprises a network of follicular dendritic cells and small resting B cells.
After an antigenic challenge, a primary follicle becomes a larger secondary follicle—a ring of concentrically packed B lymphocytes surrounding a center (the germinal center)
-Spleen
-Lymph nodes
-Associated tissue
-MALT
-GALT
-BALT
-CALT
Dr. Alok Tripathi studies immunology at the Department of Biotechnology. The document discusses the history and key concepts of immunology, including:
1. The dual immune system of vertebrates, consisting of cell-mediated and humoral immunity.
2. Early theories on immunity proposed by scientists like Metchnikoff, von Behring, and Paul Ehrlich to explain concepts like phagocytosis, humoral immunity, and the generation of antibody diversity.
3. The development of the clonal selection theory by Burnet, Jerne, and others to explain how the immune system achieves antigen specificity through clonal expansion and memory cells.
The document summarizes the immune system's defenses against various pathogens. It describes both innate and acquired immunity. The innate immune system provides non-specific defenses like physical barriers, chemicals, and phagocytosis. The acquired immune system mounts pathogen-specific responses through antibodies, B cells, T cells, and cytokines. Together these defenses protect the body from bacteria, viruses, and parasites through mechanisms like inflammation, phagocytosis, and cell-mediated or antibody-mediated immunity.
18. Immune Responses to Infectious diseases.pdfbriankash1
Our body's immunity has different means of showing response to pathogens be it virus, bacteria, fungi or parasite by involving the functions of innate and adapted immunity. Some of these pathogens have adopoted means to evade host's immunity system making them survive and cause diseases.
The mouth, like all external surfaces of the body and the gut,
has a substantial microflora living in symbiosis with a healthy
host.
• The microflora of the mouth contains hundreds of species of
aerobic and anaerobic bacteria.
• Cultural studies indicate that more than 500 distinct microbial
species can be found in dental plaque.
5
• Although bacteria are necessary for periodontal disease to
take place, a susceptible host is also needed.
• The immune-inflammatory response that develops in the
gingival and periodontal tissues in response to the chronic
presence of plaque bacteria results in destruction of
structural components of the periodontium leading,
ultimately, to clinical signs of periodontitis.
6
• The host response is essentially protective, but both
hyporesponsiveness and hyper-responsiveness of certain
pathways can result in enhanced tissue destruction (Bruce
Pihlstrom 2005 ).
• Closer investigations of the destructive pathway of periodontal
disease began to focus on the relation-ship between bacteria
and the host response in the initiation and progression of
periodontal disease.
7
• This shift in etiological theory produced a paradigm that
called attention to the fact that although microorganisms are
the cause of periodontitis, the clinical expression of the disease
depends on how the host responds to the extent and virulence
of the microbial burden.
• It was found that degradation of host tissue results from this
bacterial-host interaction.
The immune response to extracellular bacteria involves antibodies targeting bacterial capsular polysaccharides, exotoxins, and extracellular enzymes. Complement activation promotes opsonization and lysis of bacteria, and recruits phagocytic cells to the infection site. Neutrophils, monocytes, and macrophages phagocytose and kill ingested extracellular bacteria through microbicidal actions. Complement activation and phagocytosis are key innate immune responses that help rid the body of invading extracellular bacteria.
Immunity is the balanced state of multicellular organisms having adequate biological defenses to fight infection, disease, or other unwanted biological invasion, while having adequate tolerance to avoid allergy, and autoimmune diseases.
Immune response during bacterial, parasitic and viral infection.pptxVanshikaVarshney5
1) The innate immune response to viruses involves interferon production which stimulates antiviral proteins to block viral replication. Natural killer cells also help destroy infected cells.
2) The adaptive immune response involves humoral immunity with antiviral antibodies that neutralize viruses and prevent infection of cells. Cell-mediated immunity uses cytotoxic T-cells and macrophages to directly kill infected cells.
3) Viruses have evolved mechanisms to evade the immune response, such as reducing MHC expression to avoid detection by T-cells, direct immunosuppression, and antigenic variation for influenza virus.
The document summarizes the immune response to different infectious agents including viruses, bacteria, fungi, parasites. It discusses both the innate and adaptive immune responses targeting each type of pathogen. It also describes mechanisms pathogens use to evade the host immune response, such as antigenic variation, inhibiting phagocytosis, and surface structures that prevent complement activation. Tissue damage during infection can be caused by either the pathogen itself or the host immune response.
The immune system responds to different microbes through innate and adaptive immunity. Innate immunity uses mechanisms like phagocytosis, inflammation, and complement activation to respond quickly. Adaptive immunity produces antibodies and T cells for long-lasting protection. Extracellular bacteria are targeted by antibodies, phagocytes, and the complement system. Intracellular bacteria are responded to by NK cells, phagocytes, and CD8 T cells that activate macrophages. Viruses induce type I interferons and are targeted by antibodies and cytotoxic T lymphocytes that kill infected cells. Microbes have evolved ways to evade these immune responses like altering antigens, inhibiting antigen presentation, or infecting immune cells.
Innate immunity provides non-specific protection against pathogens and involves physical and chemical barriers as well as cellular responses. Adaptive immunity provides pathogen-specific protection through antibodies and T-cells, develops over time, and results in immunological memory. Innate immunity forms the first line of defense through mechanisms like epithelial surfaces, antimicrobial proteins, inflammation, and phagocytosis. Adaptive immunity is subdivided into active and passive immunity and involves both humoral and cell-mediated responses that are stimulated by antigens.
Hypersensitivity reactions (immunologic tissue injury) - PHARM DJuliya Susan Reji
Immune tolerance is the ability of the immune system to distinguish self from non-self and not mount an immune response against self-antigens. It occurs through clonal elimination of self-reactive T cells in the thymus, clonal anergy where self-reactive T cells are nonresponsive, and suppressor T cells that inhibit self-reactive T cell responses. Hypersensitivity reactions occur when the immune system mounts an exaggerated response against antigens and causes tissue damage. The four types of hypersensitivity reactions are classified based on the mechanisms and temporal onset of the immune response.
Microbes, Man and Environment (Microbial pathogenicity) .pptxMidhatSarfraz
The document discusses microbial pathogenicity and the progression of infection and disease. It provides details on:
1) The factors that influence a microbe's pathogenicity, including host factors like age and immune status, and microbial factors like virulence factors and inoculum size.
2) The steps in pathogenesis which include a microbe gaining access to the host, adhering to tissues, penetrating defenses, and damaging the host directly or through toxins.
3) The two qualities that allow microbes to cause disease - invasiveness and toxigenesis. It also discusses bacterial adherence, biofilm formation, and how pathogens prevent host defenses.
Immunity
Definitions
Components of Immune system
Types
Innate immunity and Mechanism
Adaptive immunity and Mechanism
2. Antigen
Origin of Antigen
Immunogen
3. Antibody- Immunoglobulin
- Structure
- Classification
- Function of each antibody
Bacterial pathogenesis is a complicated process. On encountering a host, pathogenic microorganisms must first adapt to life on the host surface and survive long enough to initiate an infection.
Vaccines work by inducing active immunity through antibody and cell-mediated immune responses. Antibodies are produced by B cells to help eliminate antigens, while T cells have cytotoxic and helper functions. There are two main types of vaccines - live attenuated vaccines, which activate all phases of the immune system but carry a risk of mutation; and inactivated vaccines, which are safer but require boosters. An ideal vaccine would provide lifelong protection against all variants of a pathogen by preventing disease transmission through rapid, effective, and safe induction of immunity in all individuals.
Microbial interactions with the host in periodontal diseaseDr Heena Sharma
This document summarizes the microbial and host interactions that determine the progression of periodontal diseases. It discusses how bacteria colonize surfaces in the oral cavity and invade host tissues. Virulence factors like adhesins, proteases and toxins enable pathogenic bacteria to cause direct tissue damage or stimulate the host immune response. The host response is mediated by innate immune cells like neutrophils and macrophages, as well as cytokines and proteinases that can contribute to periodontal tissue destruction. Certain bacterial pathogens are also able to evade or suppress the host immune response to enhance their survival in the periodontal environment.
The document summarizes key aspects of innate immunity in 3 paragraphs or less:
Innate immunity provides the first line of defense against pathogens and includes physical barriers and fixed mechanisms that are always ready. It responds immediately through mechanisms like antimicrobial peptides, complement proteins that tag pathogens, and pattern recognition receptors on macrophages that help clear infections. Phagocytes like macrophages and neutrophils work to eliminate invading pathogens through receptors, phagocytosis, and secretion of inflammatory cytokines and chemokines to recruit more immune cells. Together the fixed and cellular defenses of innate immunity function to quickly control infections before the adaptive immune response is deployed.
This slide covers briefly how intracellular and extracellular bacteria elicits an immune response, how bacteria evade from the immune system, what complement system is, opsonization, neutralisation, septic shock, sepsis, superantigens, phagocytosis, interleukins, Toll-like receptors, a list of diseases caused by bacterias and their names etc.
PATHOGENICITY by Mathan.S, 1st M.Sc Microbiology, Sri Paramakalyani College MathanS22
Pathogenicity pertains to the ability of a pathogenic agent to cause disease. Examples of pathogenic agents are infectious bacteria, viruses, prions, fungi, viroids, and parasites causing disease.
This document discusses bacterial pathogenicity and virulence factors. It begins with defining key terms like pathogenesis, virulence, and types of bacterial pathogens. It then covers various requirements for bacterial pathogenicity like adhesion, invasion, multiplication, and tissue destruction. The document discusses several virulence factors like capsules, cell wall proteins, cytotoxins, fimbriae, biofilms, and exotoxins that allow bacteria to evade host defenses and cause disease. It also covers concepts like quorum sensing, bacterial secretion systems, and mechanisms of bacterial infection and colonization.
This document discusses several common zoonotic diseases including their causative agents, modes of transmission, signs and symptoms, and methods of diagnosis and treatment. Plague is caused by Yersinia pestis and transmitted via flea bites, presenting as bubonic, pneumonic, or septicemic plague. Tularemia caused by Francisella tularensis is transmitted by ticks or infected animals and presents as ulceroglandular or typhoidal disease. Lyme disease, caused by the spirochete Borrelia burgdorferi, causes an erythema migrans rash and can lead to joint, heart, or neurological involvement.
1. Systemic inflammatory response syndrome (SIRS) is a clinical syndrome characterized by generalized inflammation in organs remote from the initial insult, caused by deregulated inflammation.
2. SIRS can be triggered by infectious processes like sepsis or non-infectious insults and is characterized by fever, hypotension, tachycardia, tachypnea, and leukocytosis.
3. Untreated, SIRS can lead to multiple organ dysfunction syndrome (MODS) through the massive release of pro-inflammatory mediators, resulting in organ damage and extremely high mortality rates.
This document discusses process improvement in quality management systems. It outlines Deming's Plan-Do-Check-Act model for continual process improvement. Key aspects of process improvement include identifying problems, developing improvement plans, implementing plans, reviewing effectiveness through audits, and adjusting plans based on results. Quality indicators are important tools that provide measurable information on performance to identify areas for improvement. Selecting the right quality indicators and developing them successfully is also discussed.
This document provides an overview of mycology, which is the study of fungi. It discusses the classification, morphology, and types of fungal infections that affect the skin, nails, hair (dermatophytes), subcutaneous tissues, and internal organs/systems (systemic and opportunistic fungi). Common fungal infections discussed include dermatophytosis, tinea versicolor, tinea nigra, sporotrichosis, chromomycosis, mycetoma, blastomycosis, histoplasmosis, and coccidioidomycosis. The document also covers the laboratory diagnosis and treatment of various mycoses. The lecture objectives are to describe the classification of fungal infections,
This document provides an overview of diagnostic microbiology. It discusses the goals of clinical microbiology laboratories in testing specimens to identify microorganisms causing illness and providing antimicrobial susceptibility results. It also describes various laboratory procedures used, including microscopy, culture-based techniques, immunological and molecular assays. Specimen collection, processing, staining methods, and interpretation of culture results are discussed in detail.
The document discusses clinical microbiology and the diagnosis of infectious diseases. It covers the following key points in 3 sentences:
Clinical specimens must be properly collected, transported, and processed to accurately diagnose infectious diseases. A variety of specimen types can be used to identify different types of bacterial, fungal, parasitic and viral infections. The clinical microbiology laboratory works to isolate, identify, and test pathogens from specimens to assist clinicians in diagnosing and treating infectious diseases.
The document provides an overview of infectious diseases presented by Dr. Fatima Fasih. It discusses the historical perspective of infectious diseases including the contributions of Robert Koch and the Koch Postulates. The document also covers classifications of infectious agents such as viruses, bacteria, fungi, protozoa, and helminths. It examines how these microbes are transmitted and the mechanisms by which they cause disease, and also addresses emerging infectious diseases.
Bronchopneumonia and lobar pneumonia are two main types of pneumonia. Bronchopneumonia is a patchy pneumonia localized around the bronchioles and surrounding alveoli, often seen in infants and the elderly. It spreads from the bronchioles to nearby alveoli. Lobar pneumonia involves consolidation of an entire lung lobe or more. It is typically caused by Streptococcus pneumoniae and presents with high fever, shaking chills, and cough producing mucopurulent sputum. Other types of pneumonia discussed include community-acquired bacterial pneumonia, community-acquired viral pneumonia, hospital-acquired pneumonia, and aspiration pneumonia.
This document discusses water bacteriology and the use of fecal indicator bacteria to detect contamination. It describes the criteria for a good indicator bacteria, including being present in high numbers in feces. It outlines the most commonly used indicators: total coliforms, E. coli, and enterococci. The document also details methods for detecting these indicators, such as membrane filtration and culture media like EMB agar. It provides definitions and procedures for microbiological water testing and interpreting results.
How to Add Chatter in the odoo 17 ERP ModuleCeline George
In Odoo, the chatter is like a chat tool that helps you work together on records. You can leave notes and track things, making it easier to talk with your team and partners. Inside chatter, all communication history, activity, and changes will be displayed.
Executive Directors Chat Leveraging AI for Diversity, Equity, and InclusionTechSoup
Let’s explore the intersection of technology and equity in the final session of our DEI series. Discover how AI tools, like ChatGPT, can be used to support and enhance your nonprofit's DEI initiatives. Participants will gain insights into practical AI applications and get tips for leveraging technology to advance their DEI goals.
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How to Make a Field Mandatory in Odoo 17Celine George
In Odoo, making a field required can be done through both Python code and XML views. When you set the required attribute to True in Python code, it makes the field required across all views where it's used. Conversely, when you set the required attribute in XML views, it makes the field required only in the context of that particular view.
LAND USE LAND COVER AND NDVI OF MIRZAPUR DISTRICT, UPRAHUL
This Dissertation explores the particular circumstances of Mirzapur, a region located in the
core of India. Mirzapur, with its varied terrains and abundant biodiversity, offers an optimal
environment for investigating the changes in vegetation cover dynamics. Our study utilizes
advanced technologies such as GIS (Geographic Information Systems) and Remote sensing to
analyze the transformations that have taken place over the course of a decade.
The complex relationship between human activities and the environment has been the focus
of extensive research and worry. As the global community grapples with swift urbanization,
population expansion, and economic progress, the effects on natural ecosystems are becoming
more evident. A crucial element of this impact is the alteration of vegetation cover, which plays a
significant role in maintaining the ecological equilibrium of our planet.Land serves as the foundation for all human activities and provides the necessary materials for
these activities. As the most crucial natural resource, its utilization by humans results in different
'Land uses,' which are determined by both human activities and the physical characteristics of the
land.
The utilization of land is impacted by human needs and environmental factors. In countries
like India, rapid population growth and the emphasis on extensive resource exploitation can lead
to significant land degradation, adversely affecting the region's land cover.
Therefore, human intervention has significantly influenced land use patterns over many
centuries, evolving its structure over time and space. In the present era, these changes have
accelerated due to factors such as agriculture and urbanization. Information regarding land use and
cover is essential for various planning and management tasks related to the Earth's surface,
providing crucial environmental data for scientific, resource management, policy purposes, and
diverse human activities.
Accurate understanding of land use and cover is imperative for the development planning
of any area. Consequently, a wide range of professionals, including earth system scientists, land
and water managers, and urban planners, are interested in obtaining data on land use and cover
changes, conversion trends, and other related patterns. The spatial dimensions of land use and
cover support policymakers and scientists in making well-informed decisions, as alterations in
these patterns indicate shifts in economic and social conditions. Monitoring such changes with the
help of Advanced technologies like Remote Sensing and Geographic Information Systems is
crucial for coordinated efforts across different administrative levels. Advanced technologies like
Remote Sensing and Geographic Information Systems
9
Changes in vegetation cover refer to variations in the distribution, composition, and overall
structure of plant communities across different temporal and spatial scales. These changes can
occur natural.
This presentation includes basic of PCOS their pathology and treatment and also Ayurveda correlation of PCOS and Ayurvedic line of treatment mentioned in classics.
How to Fix the Import Error in the Odoo 17Celine George
An import error occurs when a program fails to import a module or library, disrupting its execution. In languages like Python, this issue arises when the specified module cannot be found or accessed, hindering the program's functionality. Resolving import errors is crucial for maintaining smooth software operation and uninterrupted development processes.
The simplified electron and muon model, Oscillating Spacetime: The Foundation...RitikBhardwaj56
Discover the Simplified Electron and Muon Model: A New Wave-Based Approach to Understanding Particles delves into a groundbreaking theory that presents electrons and muons as rotating soliton waves within oscillating spacetime. Geared towards students, researchers, and science buffs, this book breaks down complex ideas into simple explanations. It covers topics such as electron waves, temporal dynamics, and the implications of this model on particle physics. With clear illustrations and easy-to-follow explanations, readers will gain a new outlook on the universe's fundamental nature.
2. Introduction
▶ The development of an infectious disease in an individual involves complex
interactions between the microbe and the host. The key events during
infection include:
▶ entry of the microbe
▶ invasion and colonization of host tissues
▶ evasion of host immunity
▶ tissue injury or functional impairment
▶ Microbes produce disease by:
▶ directly killing the host cells they infect
▶ liberating toxins that can cause tissue damage and functional derangements in
neighboring or distant cells and tissues that are not infected
▶ stimulating immune responses that injure both the infected tissues and normal tissues.
2/4/2023 immune invasion by microbes 2
3. General Features of Immune Responses to
Microbes
▶ Defense against microbes is mediated by the effector mechanisms of innate and
adaptive immunity.
▶ The immune system responds in specialized and distinct ways to different types of
microbes to most effectively combat these infectious agents.
▶ The survival and pathogenicity of microbes in a host are critically influenced by the
ability of the microbes to evade or resist the effector mechanisms of
immunity.
2/4/2023 immune invasion by microbes 3
4. General Features of Immune Responses to
Microbes
▶ Many microbes establish latent, or persistent, infections in which the immune
response controls but does not eliminate the microbe and the microbe survives
without propagating the infection.
▶ In many infections, tissue injury and disease may be caused by the host
response to the microbe rather than by the microbe itself.
▶ Inherited and acquired defects in innate and adaptive immunity are important
causes of susceptibility to infections
2/4/2023 immune invasion by microbes 4
5. Immunity to Extracellular Bacteria
Replicate outside the host cells e.g.,
▶ circulation
▶ connective tissues
▶ in tissue spaces : lumens of the airways, gastrointestinal tract
• Induce inflammation: tissue destruction at the site of infection
• Production toxins :diverse pathologic effects, cytotoxic and kill
the cells
• Endotoxin : bacterial cell wall component e.g., LPS from gram negative bacteria can activate MØ
and DC
• Exotoxin: bacterial secretion
2/4/2023 immune invasion by microbes 5
6. Immunity to Extracellular Bacteria
• Innate Immunity to Extracellular Bacteria:
• ▶ The principal mechanisms of innate immunity to extracellular bacteria are
complement activation, phagocytosis, and the inflammatory response.
Complement activation:
Activator:
• ▶ Peptidoglycans in the cell walls of Gram-positive bacteria
• ▶ LPS in Gram-negative bacteria
• ▶ Mannose on bacterial surface
Result of complement activation:
• ▶ Opsonization & enhanced phagocytosis of the bacteria
• ▶ Membrane attack complex : lyses bacteria
• ▶ Complement byproducts: stimulate inflammatory response
2/4/2023 immune invasion by microbes 6
7. Immunity to Extracellular Bacteria
▶ Activation of phagocytes and inflammation:
▶ Phagocytes (neutrophils and macrophages) use surface receptors to recognize
extracellular bacteria:
▶ Mannose receptors
▶ Scavenger receptors
▶ Fc receptors (opsonized bacteria)
▶ Complement receptors (opsonized bacteria)
▶ Microbial products activate Toll-like receptors (TLRs) and various cytoplasmic
sensors in phagocytes.
2/4/2023 immune invasion by microbes 7
8. Immunity to Extracellular Bacteria
of the microbes (e.g., mannose receptors, scavenger
▶ Receptors function mainly to
▶ promote the phagocytosis
receptors);
▶ stimulate the microbicidal activities of the phagocytes (mainly TLRs); and
▶ promote both phagocytosis and activation of the phagocytes (Fc and complement
receptors)
▶ Dendritic cells and phagocytes that are activated by the microbes secrete
cytokines, which induce leukocyte infiltration into sites of infection
(inflammation). The recruited leukocytes ingest and destroy the bacteria.
2/4/2023 immune invasion by microbes 8
9. Immunity to Extracellular Bacteria
▶ Adaptive Immunity to Extracellular Bacteria:
▶ Humoral immunity is a major protective immune response against
extracellular
bacteria, and it functions to-
▶ block infection,
▶ eliminate the microbes, and
▶ neutralize their toxins.
▶ Directed against cell wall antigens, secreted and cell-associated toxins▶
Neutralization: high affinity IgG, IgM, IgA (mucosal lumens)
Opsonization & phagocytosis : IgG
Classical complement activation pathway: IgM and IgG
2/4/2023 immune invasion by microbes 9
10. Immunity to Extracellular Bacteria
The protein antigens of
extracellular bacteria also
activate CD4+ helper T
cells, which produce
cytokines that induce local
inflammation, enhance the
phagocytic
microbicidal
macrophages
and
activities of
and
neutrophils, and stimulate
antibody production.
FIGURE: Adaptive immune responses to extracellular microbes. Adaptive immune responses to extracellular microbes
such as bacteria and their toxins consist of antibody production (A) and the activation of CD4+ helper T cells (B).
2/4/2023 immune invasion by microbes 10
11. Immune Evasion by Extracellular Bacteria
The virulence of extracellular bacteria has been linked to a number of
mechanisms that enable the microbes to resist innate immunity.
▶ Evading phagocytosis:
Capsule gives poor phagocyte adherence
Capsule does not adhere readily to phagocytic cells and covers carbohydrate molecules
on the bacterial surface which could otherwise be recognized by phagocyte receptors.
Many pathogens evolve capsules which physically prevent access of phagocytes to C3b
deposited on the bacterial cell wall.
Some microbes produce exotoxin that poisons phagocyte
Some other microbe attaches to surface component to enter non-phagocytic
cell
2/4/2023 immune invasion by microbes 11
12. Immune Evasion by Extracellular Bacteria
▶ Challenging the complement system:
Poor activation of complement
Capsule provides non-stabilizing surface for alternative pathway convertase.
Accelerating breakdown of complement by action of microbial products.
Certain bacterial surface molecules, notably those rich in sialic acid, bind factor H,
which then acts as a focus for the degradation of C3b by the serine protease factor I.
Some strains downregulate complement activation by interacting with C4BP; acting
as a cofactor for factor I-mediated degradation of the C4b component of the
classical pathway C3 convertase C4b2a.
C4BP can also inhibit activation of the alternative pathway.
Certain bacterial strains produce a C5a-ase which may act as a virulence factor by
proteolytically cleaving and thereby inactivating C5a.
2/4/2023 immune invasion by microbes 12
13. Immune Evasion by Extracellular Bacteria
▶ Challenging the complement system:
Complement deviation
Some species manage to avoid lysis by deviating the complement activation site
either to a secreted decoy protein or to a position on the bacterial surface distant
from the cell membrane.
Resistance to insertion of terminal complement components (MAC)
Gram-positive organisms have evolved thick peptidoglycan layers which prevent
the insertion of the lytic C5b-9 membrane attack complex into the bacterial cell
membrane.
Many capsules do the same.
2/4/2023 immune invasion by microbes 13
14. Figure: Avoidance strategies by extracellular bacteria. (a) Capsule gives poor phagocyte adherence.(b) Exotoxin poisons
phagocyte. (c) Microbe attaches to surface component to enter non-phagocytic cell. (d) Capsule provides non-stabilizing
surface for alternative pathway convertase. (e) Accelerating breakdown of complement by action of microbial products. (f)
Complement effectors are deviated from the microbial cell wall. (g) Cell wall impervious to complement membrane attack
complex (MAC).
2/4/2023 immune invasion by microbes 14
15. Immune Evasion by Extracellular Bacteria
▶ Antigenic variations:
Variation of surface lipoproteins in the lyme disease spirochete Borrelia burgdorferi
Alterations in enzymes involved in synthesizing surface structures in
Campylobacter jejuni
Antigenic variation of the pili in Neisseria meningitides
▶ Interfering with internal events in the macrophage:
Enteric Gram-negative bacteria in the gut have developed a number of ways of
influencing macrophage activity, including
Apoptosis
enhancing the production of IL-1
preventing phagosome-lysosome fusion
and affecting the actin cytoskeleton.
immune invasion by microbes 15
16. Immunity to Intracellular Bacteria
▶ A characteristic of facultative intracellular bacteria is their ability to survive and
even to replicate within phagocytes. Because these microbes are able to find a
niche where they are inaccessible to circulating antibodies, their elimination
requires the mechanisms of cell-mediated immunity.
▶ Innate Immunity to Intracellular Bacteria:
▶ The innate immune response to intracellular bacteria is mediated mainly by
phagocytes and natural killer (NK) cells.
▶ Phagocytes, initially neutrophils and later macrophages, ingest and attempt to
destroy these microbes, but pathogenic intracellular bacteria are resistant to
degradation within phagocytes. Products of these bacteria are recognized by TLRs
and cytoplasmic proteins of the NOD-like receptor (NLR) family, resulting in
activation of the phagocytes.
2/4/2023 immune invasion by microbes 16
17. Immunity to Intracellular Bacteria
▶ Intracellular bacteria activate NK cells by inducing expression of NK cell–activating
ligands on infected cells and by stimulating dendritic cell and macrophage
production of IL-12 and IL-15, both of which are NK cell– activating cytokines.
▶ The NK cells produce IFN-γ, which in turn activates macrophages and promotes
killing of the phagocytosed bacteria. Thus, NK cells provide an early defense against
these microbes, before the development of adaptive immunity.
▶ However, innate immunity usually fails to eradicate the infections, and eradication
requires adaptive cell-mediated immunity.
2/4/2023 immune invasion by microbes 17
18. Immunity to Intracellular Bacteria
▶ Adaptive Immunity to Intracellular Bacteria:
▶ The major protective immune response against intracellular bacteria is T cell–
mediated recruitment and activation of phagocytes (cell-mediated immunity).
▶ T cells provide defense against infections by two types of reactions:
▶ CD4+ T cells activate phagocytes through the actions of CD40 ligand and IFN-γ; these
two stimuli activate macrophages to produce several microbicidal substances, including
reactive oxygen species, nitric oxide, and lysosomal enzymes and resulting in killing of
microbes that are ingested by and survive within phagocytes. IFN-γ also stimulates the
production of antibody isotypes that activate complement and opsonize bacteria for
phagocytosis, thus aiding the effector functions of macrophages.
▶ CD8+ cytotoxic T lymphocytes (CTLs) kill infected cells, eliminating microbes that
escape the killing mechanisms of phagocytes.
2/4/2023 immune invasion by microbes 18
19. Immunity to Intracellular Bacteria
▶ Phagocytosed bacteria stimulate CD8+ T cell responses if bacterial antigens are
transported from phagosomes into the cytosol or if the bacteria escape from
phagosomes and enter the cytoplasm of infected cells.
▶ In the cytosol, the microbes are no longer susceptible to the microbicidal
mechanisms of phagocytes, and for eradication of the infection, the infected cells
have to be killed by CTLs.
▶ The macrophage activation that occurs in response to intracellular microbes is
capable of causing tissue injury.
2/4/2023 immune invasion by microbes 19
20. Immunity to Intracellular Bacteria
FIGURE: Cooperation of CD4+ and CD8+ T cells in defense against intracellular microbes.
2/4/2023 immune invasion by microbes 20
21. Immunity to Intracellular Bacteria:
Mycobacterium tuberculosis.
▶ Tuberculosis (TB) is on the rampage, aided by
the emergence of multidrug-resistant strains of
Mycobacterium tuberculosis.
▶ Mechanism
(a) Specific CD4 Th1 cell recognizes mycobacterial
peptide associated with MHC class II and releases MØ
activating IFNγ. (b) The activated MØ kills the
intracellular TB, mainly through generation of toxic
NO.. (c) A 'senile' MØ, unable to destroy the
intracellular bacteria, is killed by CD8 and CD4
cytotoxic cells and possibly by IL-2-activated NK
cells. The MØ then releases live tubercle bacilli which
are taken up and killed by newly recruited MØ
susceptible to IFNγ activation (d).
Figure: The 'cytokine connection': nonspecific macrophage killing of intracellular
bacteria triggered by a specific T-cell-mediated immunity reaction
2/4/2023 immune invasion by microbes 21
22. Immune Evasion by Intracellular Bacteria
▶ Intracellular bacteria have developed various strategies to resist elimination by
phagocytes. These include inhibiting phagolysosome fusion (Mycobacterium
tuberculosis, Legionella pneumophila) or escaping into the cytosol (Listeria
monocytogenes), thus hiding from the microbicidal mechanisms of lysosomes, and
directly scavenging or inactivating microbicidal substances (Mycobacterium
leprae) such as reactive oxygen and nitrogen species.
2/4/2023 immune invasion by microbes 22
23. Immunity to Fungi
Some fungal infections are endemic, and these infections are
usually caused by
fungi that are present in the environment and whose spores enter
humans.
Other fungal infections are said to be opportunistic because the
causative agents cause mild or no disease in healthy individuals
but may infect and cause severe disease in immunodeficient
persons. A serious opportunistic fungal infection associated
with AIDS is Pneumocystis jiroveci pneumonia.
2/4/2023 immune invasion by microbes 23
24. Immunity to Fungi
▶ Innate and Adaptive Immunity to Fungi:
▶ The principal mediators of innate immunity against fungi are neutrophils and
macrophages.
▶ Phagocytes and dendritic cells sense fungal organisms by TLRs and lectin-like
receptors called dectins.
▶ Neutrophils presumably liberate fungicidal substances, such as reactive oxygen
species and lysosomal enzymes, and phagocytose fungi for intracellular killing.
▶ Cryptococcus neoformans
▶ inhibit production of TNF and IL-12 by macrophage and stimulate production of IL-10,
thus inhibiting macrophage activation.
▶ CD4+ and CD8+ T cells cooperate to eliminate the yeast forms of Cryptococcus
neoformans, which tend to colonize the lungs and brain in immunodeficient hosts.
2/4/2023 immune invasion by microbes 24
25. Immunity to Fungi
Histoplasma capsulatum
facultative intracellular parasite that lives in macrophages
eliminated by the same cellular mechanisms that are effective against intracellular bacteria.
Pneumocystis jiroveci
causes serious infections in individuals with defective cell-mediated immunity.
• Candida
mucosal surfaces and cell-mediated immunity
• Fungi also elicit specific antibody responses that may be of
protective value.
2/4/2023 immune invasion by microbes 25