MAJOR HISTOCOMPATIBI LITY 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 Pattern is unique to individual Set of unique markers on human cells = major histocompatibility complex (MHC). IMMUNE RESPONSE Respond against/eliminate foreign agents Protein
toxin molecule Virus Infectious bacterium Lack of MHC = Lack of immune response 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 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
MHCS WHICH CELLS EXPRESS MCH I/II? All nucleated cells = equally express BOTH sets of just MCH I 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 AntigenPresenting Cells (APC) ANTIGEN-PRESENTING CELLS Can present parts of proteins taken up by the ACP to T lymphocytes.
NON-SPECIFIC MECHANISM First line of defense Physical barriers of the body Skin Mucous Tears Saliva pH of skin
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 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 2 TYPES OF RESPONSES TO ANTIGENS 1. Humoral immunity
-B Cell activation -Production of antibodies 2. Cell-mediated response - Production of Cytotoxic T Cells HUMORAL IMMUNE RESPONSE Antibodies produced Bind to antigens = easier targets for phagocytes. Mainly fluids free bacteria, toxins, viruses in body
HUMORAL RESPONSE 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! CYTOKINES Secreted proteins + signaling molecules Interleukin promote B cells
development and differentiation of T & 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 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 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 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 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 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
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