Innate Immunity


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Innate Immunity

  1. 1. Resistance and the Immune System: Innate Immunity Chapter 19
  2. 2. Overview of Host Immune Defenses
  3. 3. <ul><li>Blood Cells Form an Important Defense for Innate and Acquired Immunity </li></ul><ul><li>Major Components </li></ul><ul><ul><li>Serum is the fluid part of blood, containing: </li></ul></ul><ul><ul><ul><li>Minerals, salts, proteins, etc. </li></ul></ul></ul><ul><ul><li>Plasma is serum that contains clotting agents </li></ul></ul><ul><ul><li>Cells </li></ul></ul><ul><ul><ul><li>RBC </li></ul></ul></ul><ul><ul><ul><li>Platelets </li></ul></ul></ul><ul><ul><ul><li>Leukocytes (white blood cells) </li></ul></ul></ul>Overview of Host Immune Defenses
  4. 4. <ul><li>Leukocytes (white blood cells) are produced in the bone marrow </li></ul><ul><ul><li>Neutrophils (polymorphonuclear leukocytes [PMNs]) are phagocytes </li></ul></ul><ul><ul><li>Eosinophils contain toxic compounds to defend against multicellular parasites </li></ul></ul><ul><ul><li>Basophils are similar to mast cells, acting in allergic reactions </li></ul></ul>Overview of Host Immune Defenses
  5. 5. <ul><li>Monocytes are phagocytes that mature into macrophages in tissue </li></ul><ul><li>Lymphocytes move to the lymph nodes after maturation </li></ul><ul><ul><li>Natural killer (NK) cells destroy virus-infected and abnormal cells </li></ul></ul><ul><ul><li>B lymphocytes and T lymphocytes are involved in acquired immunity </li></ul></ul><ul><li>Dendritic cells are found in the skin and other points of pathogen origin </li></ul><ul><ul><li>They are involved in acquired immunity </li></ul></ul>Overview of Host Immune Defenses
  6. 6. <ul><li>Lymphoid organs are the site of maturation, development and proliferation of lymphocytes </li></ul><ul><li>The primary lymphoid tissues are the thymus and bone marrow </li></ul><ul><li>The secondary lymphoid tissues are the spleen and lymph nodes </li></ul><ul><ul><li>The spleen contains cells that monitor and fight infectious microbes </li></ul></ul><ul><ul><li>The lymph nodes contain phagocytes and lymphocytes </li></ul></ul>Overview of Host Immune Defenses
  7. 7. <ul><li>The interactions between innate and acquired immunity make infections and disease establishments difficult </li></ul><ul><li>Innate immunity (nonspecific resistance) is genetically-encoded to recognize common pathogenic features and foreign substances; host’s “early-warning system” </li></ul><ul><ul><li>Skin, interferon, lysozyme, phagocytes </li></ul></ul><ul><ul><li>Cytokines are chemical signals sent by many immune cells to tissues involved with initiating acquired immunity; released by defensive cells in response to an activating substance (pathogen) </li></ul></ul><ul><li>Acquired immunity (specific resistance) involves production of: </li></ul><ul><ul><ul><li>Antibodies, action of complement System, Cellular immunity, Killer T-lymphocytes </li></ul></ul></ul>Innate and Acquired Immunity
  8. 8. <ul><li>Species Immunity: disease affecting one species will not affect another </li></ul><ul><li>Behavioral Immunities: exist among various races and people of the world (related to a people’s way of life) </li></ul><ul><li>Racial Immunities: reflect the evolution of resistant humans </li></ul><ul><li>Population Immunities: some parasites adapt to certain body environment </li></ul>Types of Non-Specific Resistance
  9. 9. <ul><li>Mechanical barriers </li></ul><ul><ul><li>Skin: breaches of the skin may allow microbes to enter the blood </li></ul></ul><ul><ul><li>Mucous membranes </li></ul></ul><ul><li>Chemical Barriers </li></ul><ul><ul><li>pH: acidity </li></ul></ul><ul><ul><li>Defensins: antimicrobial peptides found in secretions </li></ul></ul><ul><ul><li>Lysozyme: tears, saliva, sweat </li></ul></ul><ul><ul><li>Interferons: interfere with viral reproduction </li></ul></ul><ul><li>Microbiological barriers: normal microbiota </li></ul>The Innate Immune Response
  10. 10. <ul><li>Phagocytosis is the capture and digestion of foreign particles </li></ul><ul><li>Chemokines are cytokines that attract macrophages and neutrophils to infected tissues </li></ul><ul><li>Opsonins attach to microbes to increase the ability of phagocytes to adhere (opsonization) </li></ul>Phagocytosis
  11. 11.
  12. 12. Inflammation
  13. 13. <ul><li>Low to moderate fever supports the immune system by: </li></ul><ul><ul><li>inhibiting rapid microbial growth </li></ul></ul><ul><ul><li>encouraging rapid tissue repair </li></ul></ul><ul><ul><li>heightening phagocytosis </li></ul></ul><ul><li>Pyrogens are cytokines produced by: </li></ul><ul><ul><ul><li>some leukocytes </li></ul></ul></ul><ul><ul><ul><li>fragments from pathogens </li></ul></ul></ul><ul><ul><li>They affect the hypothalamus, causing elevated body temperature </li></ul></ul><ul><li>If a temperature rises above 40°C in an adult, host metabolic inhibition can occur </li></ul><ul><ul><li>This can cause convulsions and death </li></ul></ul>Fever
  14. 14. <ul><li>NK cells are formed in the bone marrow, and migrate to: tonsils, lymph nodes and spleen </li></ul><ul><li>When activated, they produce cytokines that trigger response by macrophages and other cells </li></ul><ul><li>They move into blood and lymph where they kill cancer cells and virus-infected cells </li></ul><ul><li>Not phagocytic, contain on their surfaces special receptors capable of forming cell-to-cell interactions with a target cell </li></ul><ul><ul><li>Cytolytic mediators: perforins, granzymes </li></ul></ul>Natural Killer Cells
  15. 15.
  16. 16. <ul><li>Complement is a series of proteins that circulate in the bloodstream that represents another innate defense to disease. </li></ul><ul><ul><li>They activate in the presence of microbes in a cascade of steps that assist inflammatory response and phagocytosis. </li></ul></ul><ul><li>In the classical pathway , antibody-microbe complexes activate complement proteins that activate C3 convertase </li></ul><ul><li>In the alternative pathway , the complement protein C3 binds to the pathogen cell surface to activate C3 convertase </li></ul>Complement System
  17. 17.
  18. 18. <ul><li>The immune system responds to pathogens by rapid immune response followed by development of antibodies and lymphocytes to generate acquired immune response. </li></ul><ul><li>Pathogen-associated molecular patterns (PAMPs) help the innate immune system recognize pathogens by identifying unique microbial molecular sequences not found on host cells. </li></ul><ul><li>Toll-like receptors (TLRs) are signaling receptors on: macrophages, dendritic cells and endothelial cells </li></ul>Innate Immunity and Receptor Recognition
  19. 19. <ul><li>TLRs mediate a specific response to distinct PAMPs </li></ul><ul><li>They stimulate the secretion of cytokines, </li></ul><ul><ul><li>For example, those that stimulate production of acute phase proteins </li></ul></ul><ul><li>The TLR response must be regulated to prevent infection and immune disorders </li></ul>