Pathology Review: Chapter 4 (Immunopathology) Disorder of the immune system 1. Hypersensitivity reactions (immunologically mediated tissue injury) 2. Autoimmune diseases 3. Possible immune disorders 4. Immunodeficiency diseases Immunologic responsiveness & major effector mechanisms - Humoral antibodies derived by B lymphocytes (B cells) - Cell mediated mechanisms involving T lymphocytes (T cells) Cell mediated immunity (CMI) Involved destruction of antigenic cells by T cells. Antibody mediated immunity (AMI) Involved destruction of antigens by antibodies produced by mature plasma cells B cell activation Mediated by dendritic and CD4 + effector cells T cell activation Involves T cell antigen receptors binding to an antigen-MHC protein complex on the surface of the body Types of mature T cells T lymphocytes arise from lymphoblast’s They possess several cell surface markers. All T cells possess T3 which is associated with a T cell antigen receptor TCR T cell antigen receptor TCR is made up of an alpha and beat polypeptide chain Each beta chain of the TCR is assembled from 4 seperate genes, each belonging to a group of genes separated into 4 regions: V, D, J, and C In gene rearrangement one gene each from the V, D, and J regions comes to lay next to each other by the elimination of the interposing DNA Cells of the immune system Helper T cells or T4 cells : Once primed by APC presentation of an antigen, they chemically stimulate proliferation of other T and B cells that have already been bound to the antigen
Helper T cells also secrete cytokines that co- stimulate other helper T cells and cytotoxic T cells Cytotoxic T cells or killer cells The only T cells that can directly attack and kill other cells Cytotoxic T cells or killer T cells bind tightly to the target cell and release perforins and granzymes from granules Some cytotoxic T cells secrete lymph toxins Memory T cells Descendants of activated T cells that are generated during the initial immune response A large number of memory cells are produced; therefore, the secondary response is enhanced and is greater than the primary response T suppressor cells Dampen both cellular and humoral immunity Immunological surveillance- maintained by T suppressor cells Most effective in recognizing tumor antigens caused by viruses and recognizing proteins in transplanted organs Graft rejection- transplant success depends on the similarity of tissues; a 75% tissue match is essential Following surgery immunosuppressive drugs kill rapidly diving cells B cells The body contains millions of different B cells each capable of responding to a specific antigen B lymphocytes mature within the bone marrow Once in the circulation, they express immunoglobulin IgM Memory B cells have a longer life span
and express membrane- bound antibody Once activated B cells differentiate into plasma cells Antibodies circulate in the blood and lymph where they bind to free
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- Fall '17
- cells, Cytotoxic T cells, Transplant Rejection, plasma cells, effector cells