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cell mediated immunity ppt 5th sem biotech
- 1. CELL MEDIATED IMMUNITY IMMUNOLOGY DIVYA K MENON IIIDC BIOTECHNOLOGY
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- 3. WHAT IS IMMUNOLOGY? Immunologyis the branch of biology and medicine that studies the immune system, it's functions, and it's role in defending against disease. It encompasses the study of the body's defense mechanisms against infection and other pathologies,including both innate and adaptive immunity. Louis Pasteur is known as the father of Immunology. Immunology is categorised into the following types: ¤ Diagnostic Immunology ¤ Clinical Immunology ¤ Eco Immunology ¤ Cancer Immunology ¤ Reproductive Immunology ¤ Developmental Immunology
- 4. IMMUNE SYSTEM ANDIMMUNITY The immune system is the body's defense system that protects us from harmful microorganisms like bacteria, viruses,fungi,and parasites. It is made up of various cells,tissues and organs that work together to detect and destroy foreign invaders. The immune response are of two types - Innate immunity and Adaptive immunity. The result of a well functioning immune system is immunity - the ability to resist infections. Immune system and immunity are crucial for keeping the body healthy and are the basis for how vaccines and immune therapies work.
- 5. Humoral Immunity isan antibody mediated response that occurs when foreign materials - antigens are detected in the body. This foreign material typically includes extracellular invaders such as bacteria.This mechanism is primarily driven by B cell lymphocytes, a type of immune cell that produces amtibodies after the detection of specific antigen. HUMORAL AND CELL MEDIATED Cell mediated immunity does not depend on antibodies for it's adaptive immune functions.it relies on the direct action of immune cells, particularly T lymphocytes, to eliminate intracellular pathogens and abnormal cells, rather than the production of antibodies. It's crucial for defending against viruses, fungi, and certain bacteria, as well as cancer cells.
- 6. LET'S LEARN MOREABOUT CELL MEDIATED IMMUNITY
- 7. Cell mediated immunityworks through the coordinated action of several immune responses.The main cell's involved in this are the T lymphocytes ,which kill the infected or abnormal cells and help regulate the immune response. And the T lymphocytes are activated by the help of Antigen presenting cells (APC),which display foreign antigens using Major histocompatability complex (MHC) molecules.Once they are activated ,they communicate and functions with the help of cytokines, which are chemical messengers.
- 8. T - LYMPHOCYTE Alsoknown as T cell, it is a type of lymphocytes ( a type of WBC) that plays an important role in the immune system. T cells are born from hematopoietic stem cells, found in the bone marrow. Developing T cells, then migrate to the thymus gland to develop (or mature) and react highly specifically agains t the particular type of antigen that initiated their development. There are three main groups of T- lymphocytes, and they are cytotoxic/killer cells, Helper T cells, and Suppressor cells. CYTOTOXIC T CELL~ Also known as Tc, CD8+ and killer T cell. They destroy virus-infected cells and tumor cells, and are also implicated in transplant rejection. These cells are defined by the expression of the CD8 protein on their cell surface. Cytotoxic T cells recognize their targets by binding to short peptides (8-11 amino acids in length) associated with MHC class I molecules, present on the surface of all nucleated cells. They also produce the key cytokines IL-2 and IFNγ. These cytokines influence the effector functions of other cells, in particular macrophages and NK cells.
- 9. HELPER T CELLS~A type of white blood cell that serves as a key mediator of immune function. Helper T cells play a central role in normal immune responses by producing factors that activate virtually all the other immune system cells. These cells include B cells, which produce antibodies needed to fight infection; cytotoxic T cells, which kill cells carrying infectious agents; and macrophages and other effector cells, which attack invading pathogens (disease-causing agents). Helper T cells express a protein called CD4 on their surface. This protein plays a critical role in helper T cell activation by binding class II major histocompatibility complex (MHC) molecules, which specialize in helping the immune system recognize foreign substances. SUPPRESSOR CELLS ~ Also known as Regulatory T cells and Tregs. They are a specialized subset of white blood cells that play a crucial role in maintaining immune system balance and preventing excessive or inappropriate immune responses. They act as immune system regulators, preventing the body's own immune cells from attacking healthy tissues (autoimmunity) and limiting inflammatory responses. MEMORY T CELLS ~ They are a type of specialized immune cell that provides long-lasting protection against previously encountered pathogens. They are formed after an initial immune response and remain in the body to quickly recognize and respond to the same pathogen if it enters again, leading to a more rapid and effective immune response
- 11. ANTIGEN PRESENTING CELLS(APC) An antigen-presenting cell (APC) or accessory cell is a cell that displays an antigen bound by major histocompatibility complex (MHC) proteins on its surface; this process is known as antigen presentation.It detects, engulfs, and informs the adaptive immune response about an infection. When a pathogen is detected, these APCs will phagocytose the pathogen and digest it to form many different fragments of the antigen. Antigen fragments will then be transported to the surface of the APC, where they will serve as an indicator to other immune cells. The three main types of antigen-presenting cells (APCs) are dendritic cells, macrophages, and B cells.
- 12. MAJOR HISTOCOMPATIBILITY COMPLEX(MHC) Major histocompatibility complex (MHC), group of genes that code for proteins found on the surfaces of cells that help the immune system recognize foreign substances. MHC proteins are found in all higher vertebrates. In human beings the complex is also called the human leukocyte antigen (HLA) system. There are two major types of MHC protein molecules—class I and class II. Class I MHC molecules span the membrane of almost every cell in an organism, while class II molecules are restricted to cells of the immune system called macrophages and lymphocytes. The MHC is also polymorphic, meaning a large number of alleles exist in the population for each of the genes. Each individual inherits a restricted set of alleles from his or her parent.
- 13. Activation of TCells T cell activation is a crucial process in the adaptive immune response, where T lymphocytes become functional and capable of initiating an immune response. This activation requires a series of carefully orchestrated signals, including antigen recognition, costimulatory signals, and cytokine signalling, which ultimately lead to T cell proliferation, differentiation, and effector function. STEP 1: ANTIGEN RECOGNIT ION STEP 2: CO-STIMULAT ION STEP 3: CYTOKINE SIGNALLING
- 14. T-cell receptors (TCRs)on T lymphocytes recognize only antigen fragments presented by APCs through MHC molecules. Unlike B cells, T cells cannot detect free antigens. This process, called MHC restriction, ensures specificity. CD8⁺ T cells recognize antigens with MHC class I, while CD4⁺ T cells recognize those with MHC class II, allowing the immune system to target infected or abnormal cells accurately. Co-stimulation is a secondary signal which immune cells rely on to activate an immune response in the presence of an antigen-presenting cell. In the case of T cells, two stimuli are required to fully activate their immune response. The co-stimulatory signal, is antigen nonspecific and is provided by the interaction between co-stimulatory molecules expressed on the membrane of the APC and the T cell. This interaction promotes and enhances the TCR signaling, but can also be bi-directional. The co-stimulatory signal is necessary for T cell proliferation, differentiation and survival. Activation of T cells without co-stimulation may lead to the unresponsiveness of the T cell (also called anergy), apoptosis or the acquisition of the immune tolerance After T cell activation, cytokines like IL-2 trigger clonal expansion, where the activated T cell multiplies into identical effector and memory cells. Depending on the cytokine signals received, helper T cells can differentiate into Th1 (promoting cell-mediated responses via IFN-γ) or Th2 (supporting humoral immunity via IL-4, IL-5). Cytotoxic T lymphocytes (CTLs) arise from CD8⁺ T cells and directly kill infected cells. This finely tuned process ensures the immune system generates the right type of response. ☛ ☛ ☛
- 15. MECHANISM The image showshow T-cells get activated during an immune response. When they encounter an antigen-presenting cell displaying antigen on MHC molecules, their receptors bind to it and get activated with the help of cytokines. 》》》》》
- 16. FUNCTIONS Defense against intracellularpathogens : CMI is essential for clearing cells that have been infected by viruses, intracellular bacteria, or fungi. Tumor surveillance : CMI helps detect and destroy cancer cells that arise in the body. Cytotoxic T cells recognize cancer-specific antigens on the surface of tumor cells and eliminate them, preventing tumor growth and metastasis. Regulation of immune responses: : T cells, especially regulatory T cells, play a role in suppressing or controlling the immune response, preventing excessive inflammation and autoimmunity. Long-term immunityCMI responses generate memory T cells that can quickly recognize and respond to the same pathogen if encountered again in the future.
- 17. CONCLUSION • Cell-mediated immunityis a vital part of the adaptive immune system involving T lymphocytes. Through antigen recognition, activation, and cytokine signaling, T cells multiply and carry out targeted responses. Helper and cytotoxic T cells coordinate to eliminate infected cells, providing strong defense and lasting protection against intracellular pathogens.
- 18. REFERENCE 1.Cavanagh, M. (Originalauthor), & Gwyer Findlay, E. (Updated). (2022). T-cell activation. British Society for Immunology. Retrieved August 11, 2025, from https://www.immunology.org/public-information/bitesized-immunology/systems-processes/t-cell -activation 2. Wikipedia Contributors. (n.d.). Cell-mediated immunity. In Wikipedia, The Free Encyclopedia. Retrieved August 11, 2025, from https://en.wikipedia.org/wiki/Cell-mediated_immunity. 3. Kaiser, G. (2023, November 2). 14.1: Cell-Mediated Immunity – An Overview. In Microbiology (Kaiser). LibreTexts. Retrieved August 11, 2025
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