Cell-mediated immunity
From Wikipedia, the free encyclopedia
Cell-mediated immunity, also known as delayed-type hypersensitivity (DTH) or Type IV Hypersensitivity, is an immune response that does not involve antibodies but rather involves the activation of macrophages, natural killer cells (NK), antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. Historically, the immune system was separated into two branches; 1. Humoral immunity, for which the protective function of immunization could be found in the humor (cell-free bodily fluid or serum), 2. Cellular immunity, for which the protective function of immunization was associated with cells. Cellular immunity protects the body by:
- activating antigen-specific cytotoxic T-lymphocytes that are able to lyse body cells displaying epitopes of foreign antigen on their surface, such as virus-infected cells, cells with intracellular bacteria, and cancer cells displaying tumor antigens;
- activating macrophages and natural killer cells, enabling them to destroy intracellular pathogens; and
- stimulating cells to secrete a variety of cytokines that influence the function of other cells involved in adaptive immune responses and innate immune responses.
Cell-mediated immunity is directed primarily at microbes that survive in phagocytes and microbes that infect non-phagocytic cells. It is most effective in removing virus-infected cells, but also participates in defending against fungi, protozoans, cancers, and intracellular bacteria. It also plays a major role in transplant rejection.
Adaptive immune system - Innate immune system - Humoral immune system - Cellular immune system
Lymphatic system - Inflammation - Complement system (Classical, Alternative, Lectin) - Cytokines - White blood cells - Antibody - Antigen - APC - MHC
Immunity - Autoimmunity - Tolerance (Central) - Immunodeficiency
