Presentation on theme: "MHCs: The Role of Cell Surface Markers. Immunity = ability to distinguish between "self" and "non-self” Every cell carries same set of distinctive."— Presentation transcript:
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).
Respond against/eliminate foreign agents Protein toxin molecule Virus Infectious bacterium Lack of MHC = Lack of immune response
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
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
All nucleated cells = equally express BOTH sets of just MCH I
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)
Can present parts of proteins taken up by the ACP to T lymphocytes.
First line of defense Physical barriers of the body Skin Mucous Tears Saliva pH of skin
2 nd 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
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
1. Humoral immunity -B Cell activation -Production of antibodies 2. Cell-mediated response - Production of Cytotoxic T Cells
Antibodies produced Bind to antigens = easier targets for phagocytes. Mainly free bacteria, toxins, viruses in body fluids
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!
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
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
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
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
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
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