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Major histocompatibility complex

Major histocompatibility complex. MHCs: The Role of Cell Surface Markers. MHC- Major Histocompatibility complex. Immunity = ability to distinguish between "self" and "non-self” Every cell carries same set of distinctive surface proteins distinguish you as "self”

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Major histocompatibility complex

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  1. Major histocompatibility complex MHCs: The Role of Cell Surface Markers

  2. MHC-Major Histocompatibility complex • Immunity = ability to distinguish between "self" and "non-self” • Every cell carries same set of distinctive surface proteins • distinguish you as "self” • Pattern is unique to individual • Set of unique markers on human cells = major histocompatibility complex (MHC).

  3. Immune response • Respond against/eliminate foreign agents • Protein toxin molecule • Virus • Infectious bacterium • Lack of MHC = Lack of immune response

  4. histocompatilibity • Similarity of patterns of MHC molecules • Skin grafts • Tissue/organ transplants • Organ transplants • Both individuals examined for genetic similarity • Blood group & MHC molecules • 10/12 matches • Medicine to lower immune response

  5. MHC Class I/II • Inherit 2 of each class (MHC I/II) • 1 from Mom • 1 from Dad • Both sets of Class I or Class II OR sometimes both are expressed on cell surface • Induction of immune response of invader • Class (I/II) expressed on surface depends on type of cell involved

  6. MHCs

  7. Which cells express MCH i/ii? • All nucleated cells = equally express BOTH sets of just MCH I

  8. Antigen-Presenting Cells • Some specialized cells of immune system = express BOTH sets of MCH I AND MCH II • B-lymphocytes • Macrophages • Certain dendritic cells • Capacity to express MHC Class II molecules  known as Antigen-Presenting Cells (APC)

  9. Antigen-Presenting Cells • Can present parts of proteins taken up by the ACP to T lymphocytes.

  10. Non-specific mechanism • First line of defense • Physical barriers of the body • Skin • Mucous • Tears • Saliva • pH of skin

  11. Non-specific mechanism • 2nd line of defense • White blood cells + inflammatory response • Phagocytosis (Neutrophils, macrophages, eosinophils) • Inflammation = blood supply increased in injured area (redness, heat) • Swelling = histamine released by basophils and mast cells, triggers inflammatory response

  12. Specific immune mechanism • Recognizes SPECIFIC foreign material and destroys it • Antibodies, Killer T cells • Active vs. Passive immunity • Active = develops after recovery disease or vaccination • Chicken pox, vaccinations (measles, mumps, rubella) • Passive = passed from one individual to another • NOT PERMANENT!Ex: Breast-feeding passes immunities to child

  13. 2 types of responses to antigens 1. Humoral immunity-B Cell activation -Production of antibodies 2. Cell-mediated response - Production of Cytotoxic T Cells

  14. Humoral IMMUNE RESPONSE • Antibodies produced • Bind to antigens = easier targets for phagocytes. • Mainly free bacteria, toxins, viruses in body fluids

  15. Humoral response

  16. Humoral Response • T-Cell (Helper T Cell) • Specifically interacts with MHC II shapes produces cytokines • Cytokines (IL-2) stimulate activated B cells to produce antibodies • Now, anywhere toxin is in system… engulfed by macrophages!

  17. Cytokines • Secreted proteins + signaling molecules • Interleukin • promote development and differentiation of T & B cells • Interleukin-1 (IL-1) • Inflammatory response (fever) • Macrophage secretes IL-1 after presenting antigen • IL-1 + presented antigen  Activates helper T Cell to produce IL-2

  18. Cytokines • Secreted proteins + signaling molecules • Interleukin • promote development and differentiation of T& B cells • Interleukin-1 (IL-1) • Inflammatory response (fever) • Macrophage secretes IL-1 after presenting antigen • IL-1 + presented antigen  Activates helper T Cell to produce IL-2 • Interleukin-2 (IL-2) “The Recruiter” • Helps B cells that have contacted antigen to differentiate into antibody-secreting plasma cells • Helps Cytotoxic T cells become active killers

  19. Cell Mediated Immune Response • Cytotoxic T cells (Killer T cells) produces killer substances • Active against viruses/bacteria within infected cells • Will be eliminated from the body • Depends on MHC Class I AND II

  20. Cell Mediated immune response • Viral proteins associate with MHC I • Transported to surface • Recognized by cytotoxic T cell (Killer T Cell) • Binds to specific fragment shape of MHC I and foreign protein shape (FITS TO ONLY FOREIGN) • ACTIVATES AND PREPARES KILLING SUBSTANCES • Waits for permission from Helper T cell

  21. Cell mediated response • Helper T Cell • Activated by interaction of APC (Antigen Presenting Cell) presenting fragments via MCH II molecules • Just like in Humoral Response! • Helper T Cell releases cytokines (IL-2) • SIGNALS KILLER T CELL TO RELEASE THE KILLING SUBSTANCES! • Kills cell that contains virus • Eventually rid body

  22. Organ transplants • MHC Class I / II expressed on surface of tissue • Different shapes than our own • Recognized by helper and killer T cells • See it as out own MHC molecules “presenting” foreign fragments • Perceived as our own tissue that is “infected” • REJECTION-IMMUNE SYSTEM ATTACKS! • 10/12 MHCs must match • Immunosuppressant medication

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