Adaptive Immunity Group Assignment BHS405 (D's Part) PDF

ADAPTIVE IMMUNITY annshafeera@FSK UiTM'09 54  Adaptive immunity n Ability of the body to defend itself against specific invading agents n Antigens (Ags) – substances recognized as foreign and provoking an immune response n Distinguished from innate immunity by n Specificit...

ADAPTIVE IMMUNITY annshafeera@FSK UiTM'09 54  Adaptive immunity n Ability of the body to defend itself against specific invading agents n Antigens (Ags) – substances recognized as foreign and provoking an immune response n Distinguished from innate immunity by n Specificity n Memory annshafeera@FSK UiTM'09 55  1. Maturation of T cells and B cells n Both develop from pluripotent stem cells originating in red bone marrow n B cells complete their development in red bone marrow n T cells develop from pre-T cells that migrate from red bone marrow to the thymus n Helper T cells (CD4 T cells) and cytotoxic T cells (CD8 T cells) n Immunocompetence – ability to carry out adaptive immune response n Have antigen receptors(make protein that r inserted into their plasma membranes): to identify specific antigen 56  2. types of adaptive immunity n Cell-mediated n Cytotoxic T cells directly attack invading antigens n Particularly effective against intracellular pathogens(viruses, bacteria,fungi), some cancer cells and foreign tissue transplants(inside cell) n Involve cells attacking cells n Antibody-mediated n B cells transform into plasma cells making antibodies (Abs) or immunoglobulins n Works against extracellular pathogens in fluids outside cells n Helper T cells aid in both types n CM & AM often work together to get rid of large no. of copies of particular antigen from th body annshafeera@FSK UiTM'09 57  Cell-mediated and antibody-mediated immunity Lymph nodes,spleen ,lymp nodules annshafeera@FSK UiTM'09 58  3. Clonal selection n Process by which a lymphocyte proliferates and differentiates (highly specialized cell) in response to a specific antigen n Clone – population of identical cells all recognizing the same antigen as original cell n Occur in secondary lymphatic organ & tissue n Indicator : swollen lymph nodes+tonsils when you were sick n Lymphocyte undergoes clonal selection to produce n Effector cell (inactivation of the antigen)– active helper T cell, active cytotoxic T cell, plasma cell, die after immune response n Memory cell – do not participate in initial immune response, respond to 2nd invasion by proliferating and differentiating into more effector and memory cells, long life spans destroy the ANTG fast & vigorous b4 any sign & symptom of disease can occur 59  4. Who is Antigens???? n Antigens have 2 characteristics n Immunogenicity – ability to provoke immune response n Reactivity – ability of antigen to react specifically with antibodies it provoked n Entire microbes may act as antigen n Typically, just certain small parts of large antigen molecule triggers response (epitope or antigenic determinant) 60  Diversity of antigen receptors n Human immune system able to recognize and bind to at least a billion different epitopes n An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells n Major Histocompatibility Complex Antigens (protein self antigen: located at the plasma membrane surface of most body cells) n MHC or human leukocyte antigens (HLA) n Normal function to help T cells recognize foreign or self 61  5. Pathways of antigen processing n B cells can recognize and bind to antigens(lymph, interstitial fluid, or blood plasma) n T cells only recognize fragments of antigens that are processed and presented in a certain way n Antigen processing n Antigenic proteins are broken down into peptide fragments and associated with MHC molecules n Antigen presentation – antigen-MHC complex inserted into plasma membrane n Pathway depends on whether antigen is outside or inside body cells 62 Antigen presenting cell: -process and present the antigen -APC’s include :dendritic cells, macrophage, B cell -location: place that antigen like to penetrate (skin: langerhans cell is dendritic cell)mucous membranes of resp, gastro, urinary, reproductive tract, lymph nodes. -post action: APC’s migrate from tissue via lymphatic vessels to lymph nodes 63  Exogenous and Endogenous Antigens n Exogenous antigens – present in fluid outside body cells n Antigen-presenting cells (APCs) include dendritic cells, macrophages and B cells n Ingest antigen, process, place next to MHC-II molecule in plasma membrane, and present to T cells n Endogenous antigens – antigens inside body cells n Infected cell displays antigen next to MHC-I AFTER PROCESS AN ANTIGEN APC MIGRATE TO LYMPHATIC TISSUE TO PRESENT ANTIGEN TO T CELLS T CELL BIND WITH ANTIGEN FRAGMENT MHC COMLEX TRIGGER CELL MEDIATD / ANTIBODY MDIATED IMMUNE RESPONSE 64 Exogenous Antigens annshafeera@FSK UiTM'09 65  Key: 5 Vesicles containing antigen Antigen peptide fragments and peptide 1 Phagocytosis or MHC-II molecules fuse fragments Exogenous 6 Antigen peptide endocytosis of antigen antigen fragments bind to MHC-II MHC-II molecules self-antigen Phagosome or endosome 7 Vesicle undergoes 2 Digestion of exocytosis and antigen into antigen–MHC-II peptide fragments complexes are inserted Antigen- 4 Packaging of MHC-II presenting molecules into a vesicle into plasma membrane cell (APC) Endoplasmic reticulum 3 Synthesis of MHC-II molecules APCs present exogenous antigens in association with MHC-II molecules Endogenous Antigens annshafeera@FSK UiTM'09 67 Cell-mediated immunity 68  Cell-mediated immunity n Activation of T cells n First signal in activation n T-cell receptors (TCRs) recognize and bind to a specific foreign antigen fragments that are presented in antigen-MHC complexes n CD4 and CD8 proteins are coreceptors n Second signal required for activation n Costimulation – 20 known substances (cytokines, plasma membrane molecules)interleukin 2 n May prevent immune response from occurring accidentally n Anergy – recognition without costimulation (in both B and T cells) leads to prolonged state of inactivity 69  Activation and clonal selection of helper T cells n Most that display CD4 develop into helper T cells (CD4 T cells) n Recognize exogenous antigen fragments associated with MHC-II molecules on the surface of an APC n After activation undergoes clonal selection n Makes active helper T cells and memory helper T cells n Function:help other cells of adaptive immune response combat intruders n Active helper T cells secrete variety of cytokines n Interleukin-2 (IL-2)(costimulator) needed for virtually all immune responses(enhance activation/poliferate of restingT,B,NK cell) n Memory helper T cells are not active cells – can quickly proliferate and differentiate if the antigen appears again annshafeera@FSK UiTM'09 70  Activation and clonal selection of cytotoxic T cells n Most that display CD8 develop into cytotoxic T cells (CD8 T cells) n Recognize antigens combined with MHC-I n Maximal activation also requires presentation of antigen with MHC-II to cause helper T cells to produce IL-2 n Undergoes clonal selection n Active cytotoxic T cells attack body cells that have been infected n Memory cytotoxic T cells do not attack but wait for a antigen to appear again annshafeera@FSK UiTM'09 72 Activation and clonal selection of a cytoxic T cell annshafeera@FSK UiTM'09 73  Elimination of invaders n Cytotoxic T cells migrate to seek out and destroy infected target cells n Kill like natural killer cells n Major difference is T cells have specific receptor for particular microbe while NK cells destroy a wide variety of microbe-infected cells n 2 ways to kill cells n Granzymes cause apoptosis (fragmentation of cellular contents) once the infected cell is destroyed the released microbs are killed by phagocytocyte n Release 2 protein from their granule : Perforin and/ or granulysin causes cytolysis (cell bursting) n Immunological surveillance n Tumor antigens displayed on cancerous cells targeted by cytotoxic T cells, macrophages and natural killer cells 74 Activity of cytoxic T cells annshafeera@FSK UiTM'09 75