Unit 2 Learning ObjectivesB and T Cell ImmunityB lymphocytes - Mature to plasma cells which then in turn secrete antibodiesAntibodies are part of humoral immunity (secreted into the bodies humors)B cells mature in the bone marrowT Lymphocytes – Cell mediated immunityCytotoxic T Cells: Kill via cell to cell interactinoHelper T Cells: Help other immune cells operate with secreation of cytokinesT cells mature in the thymusSecondary Lymphoid Organs: Lymph nodes, tonsils, spleen, lymph clusters near body linings. Lyphocytes take up residence in these organs and increase the chance they interact with their specific antigen. They can move through various lymph organs. This is where lymphocytes are activatedSpleen is lymph node of blood (cleans blood of invaders)Cytokines are used to activate B and Cytotoxic T cellsAntibodies are Y shaped proteins that are secreated by plasma cells (b cells)When a specific antigen binds to a b cell, it is then activated and it relases the specific antibody for that antigen which can then be used to tag other antigens.Immunoglobulin on membrane is the B cell receptor while immunoglobulin in bloodis the antibodiesAntibody structureFC region is the same on all antibodies, is the “stem”Antigen binds to the fab (“prongs”). The fab is different for each antibodyIgG is most common antibodieIgE is involved in allergiesEach antibody comes from a clone of plasma cells. (clone= a group of identical cells)Function of AntibodiesAct as opsonins: “prepare for eating”, it holds microbe in place for phagocyte to eatFc binds to phagocyte while fab binds to antigen. This promotes phagocytosis and links the target to the phagocyteAct to activate complement or complement systemA complement molecule binds to Fc part of antibody (fab bound to antigen) and starts a reaction. This antibody/complement complex forms a membrane attack complex (MAC) and punches holes into the cell membrane which causes cell lysis.This can occur nonspecficically with just the activated complement C1 or specificallywith antibodies.An activated C3b complex acts as an opsonin and promotes phagocytosisAntibodies can also be sued to neutralize viruses or toxins in ECFAntibody binds to toxin and then is phagocytizedCan bind to antigens and NK cellsFc binds to NK cell and fab binds to antigen. NK cell secretes chemicals which then kill the cell. This is antibody dependent cell cytotoxicityMemory CellsB cells that don’t become plasma cells first time around. Are stored and whenantigen appears again, memory cells can quickly respond (bigger and faster than 1st)First response is primary resonse while later response is secondary response.Vaccines are used to create memory cells so that when exposed to actual disease, you are prepared and don’t get the disease. (look at page 256 in course pack)T CellsT cell receptors are NOT y shapedT cell repsctors cannot bind with antigen directly, it must be processed and presented by Antigen Presenting Cells (APCs)APCs are macrophage/ dendritic cells which are found in many tissues or B cellsThe antigen is then bound to a class of Major Histocompatibility Protein Complex (MHC) These complexes are unique to everyone and they define the “self”Class II MHCs are used to present the antigen to helper T cells. They are only found in macropahges and b cells. They are the APC for helper T cells. B cell will present to helper T which will in turn cause release of cytokines. This is necessary for MAXIMUM b cell stimulation. Binds to CD4 receptor on helper TClass I MHCs (protein found in all cells with nucleus) are use to present antigen to cytotoxic t cells. Antigen is developed inside – “endogenous antigen” If a cell is infected (virus or cancer), antigen comes from inside the cells a d it is presented to cytotoxic t cell. Cytotoxic T cell CD8 receptor will bind to the antigen and destroy thecell that is presenting it. Killing is done with preforin which creates pores in the membrane NK cells kill cancer cells or other cells without antigen presenation. Kill things that donr have MHC class 1 (self)