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Transcript
Pages 415-425 Soluble proteins secreted by activated B cells or by their plasmacell offspring (in response to an antigen) They are capable of binding specifically with that antigen Also known as immunoglobulins or Igs B lymphocyte activation and clonal selection: First they bind to a specific antigen clonal selection creates copies of the activated cell this is called the primary humoral response most clones become antibody producing plasma cells other clones become memory cells memory cells provide the secondary humoral response a much faster, effective, and more prolonged response © 2015 Pearson Education, Inc. Primary response (initial encounter with antigen) Activated B cells Proliferation to form a clone Plasma cells Antigen Antigen binding to a receptor on a specific B cell (B cells with non-complementary receptors remain inactive) Memory B cell Secreted antibody molecules Secondary response (can be years later) Clone of cells identical to ancestral cells Subsequent challenge by same antigen results in more rapid response Plasma cells Secreted antibody molecules Memory B cells Relative antibody concentration in blood plasma Secondary response Primary response 0 1 2 3 4 5 Time (weeks) Antigen injected Antigen injected 6 Active immunity when B cells encounter antigens and produce antibodies acquired naturally from infection or from vaccines Most vaccines contain dead or weakened pathogens © 2015 Pearson Education, Inc. Passive Antibodies are obtained from an immune human or animal donor immunity (temporary protection) Naturally by mother to fetus via placenta; child via breast milk Artificially by way of an immune serum containing antibodies (antivenoms, antitoxins, gamma globulin) No immunological memory is established Four amino acid chains linked by disulfide bonds to form a T- or Yshaped molecule Each polypeptide chain has a variable and a constant region Constant regions determine antibody function and class © 2015 Pearson Education, Inc. Five 1. 2. 3. 4. 5. major immunoglobulin classes (MADGE): IgM—can fix complement IgA—found mainly in mucus IgD—important in activation of B cell IgG—can cross placental barrier; fixes complement IgE—involved in allergies © 2015 Pearson Education, Inc. T lymphocytes are activated indirectly: Antigens must be presented by APCs This is known as antigen presentation T cell recognizes and binds to the antigen fragment T cell also recognizes and binds to “self” glycoprotein on APC Clonal selection occurs Clones differentiate into various T cell classes © 2015 Pearson Education, Inc. Cytotoxic (killer) T cells Helper T cells Direct/manage cloning, signal with APCs, release chemicals called cytokines which increase efficiency of response Regulatory (suppressor) T cells Binds, releases lethal chemicals that degrade membrane and digest proteins Release chemicals that slow down B and T cell activity; cease the response after removal of antigen Memory cells Remember each unique antigen second response is harder, better, faster, stronger… that’s where Kanye got that song!! HUMORAL (ANTIBODY-MEDIATED) ADAPTIVE IMMUNE RESPONSE CELLULAR (CELL-MEDIATED) ADAPTIVE IMMUNE RESPONSE Antigen (1st exposure) Engulfed by Macrophage Free antigens directly activate Antigens displayed by infected cells activate Becomes Antigenpresenting cell Stimulates Helper Stimulates Stimulates B cell Cytotoxic T cell T cell Memory T cell Gives rise to Stimulates Stimulates Stimulates Antigen (2nd exposure) Stimulates Gives rise to Active cytotoxic T cells Plasma cells Secrete Memory B cells Memory T cells Antibodies Defend against extracellular pathogens by binding to antigens and making them easier targets for phagocytes and complement. Defend against intracellular pathogens and cancer by binding to and lysing the infected cells or cancer cells. Class II MHC: The main function of major histocompatibility complex (MHC) class II molecules is to present processed antigens which are derived from exogenous sources; they are critical for the initiation of the antigen-specific immune response. T cell dependent antigens Clonal Selection http://highered.mheducation.com/sites/0072507470/student_view0/chapter22/ animation__t-cell_dependent_antigens__quiz_1_.html http://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?it=swf::600::480::/ sites/dl/free/0073532215/788107/Clonal_Selection.swf::Clonal%20Selection Cell mediated Immunity https://smartsite.ucdavis.edu/access/content/user/00002950/bis10v/media/ch2 3/cell_mediated.swf Major Autografts—tissue transplanted on the same person most successful Isografts—tissue from an identical person (twin) Allografts—tissue from unrelated person types of tissue grafts most common Xenografts—tissue from a different animal species (whole organs unsuccessful) © 2015 Pearson Education, Inc. Blood group and tissue matching is done ensures the best match possible Cell membrane antigens must have a 75% match (or better) to continue with transplant immunosuppressive therapy follows © 2015 Pearson Education, Inc.