hg4_lect28免疫系統(tǒng)的遺傳學(xué)(存儲(chǔ)版)
【正文】 e is in days. Major features: ? Diversity many different pathogens recognized ? Specificity distinguishes particular molecules ? Memory responds faster with subsequent exposure Primary immune response is reaction to first exposure. Secondary immune response is reaction to exposure using “memory” of first response. Antibodies antibodies are proteins that bind to antigens antigens a protein or other molecule that causes antibody production antibody generators antibodies are produced by B cell Bcells type of lymphocyte matures in the bone marrow circulates in the blood and lymph system encounters an antigen makes a specific antibody each Bcell produces only one antibody clonal B cells are the lymphocytes that mediate the Humoral response (antibodydirected immunity). T cell lymphocytes. target and destroy infected body cells develop in the bone marrow differentiate into mature T cells in the Thymus gland T cells move in the circulation and the lymphatic system are responsible for the Cellular Response (cell mediated immunity). Antibodymediated and cellmediated immune systems work together. Humoral response Antibodydirected Immunity Three basic steps detect the antigen activate helper T cells make the antibodies Antigens activate B cells directly and indirectly HOWEVER indirect is the major pathway. Antigenpresenting macrophage activates helper T cell Role of helper T cells in the humoral response Recognize antigens presented by macrophages Stimulate B cells to produce antibodies Antibodies several different classes known as immunoglobulins, IgG, IgM, IgE, etc Antibody structure ? Antibodies minimally consist of four proteins ? Two long proteins = heavy chains ? Two shorter proteins = light chains ? Constant region of each protein is similar in all antibodies. ? Variable region of each protein is diverse. ? Antigen binding sites are pockets where antigen is held. ? Idiotypes are sites in direct contact with antigen. ? The portion of the antigen contacting the antibody is called the epitope. Problem humans produce billions of different types of antibodies Where are the genes? B cell antibody genes undergo a tremendous number of rebination events rebination occurs during B cell maturation Simplest antibody 2 H (heavy) and 2 L (light) chains random rebination can make 30,000 different H chains random rebination can make about 3600 light chains 30,000 x 3600 = 108 million binations other processes generate more than 100 trillion a particular B cells produces only one antibody as it divides its daughter cells produce the same antibody it is these mature daughter cells that are circulating Cellmediated immunity helper T cells recruit and activate B cells to make antibodies suppressor T cell inhibit immune reaction are off switches killer T cells destroy infected body cells cytotoxic T cells a subset of killer T cells memory T cells T cells ready to respond to make other T cells when antigen is reintroduced Cytotoxic T cells can destroy cancer cells Join T
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