[医药卫生]免疫学课件Antigen.ppt

Antigen 2.1 Concept of Antigen Antigens are substances that induce a specific immune response and subsequently react with the products of a specific immune response. 抗原是能够刺激机体免疫系统产生特异性免疫应答、并能与相应免疫应答产物（抗体或致敏淋巴细胞）在体内外发生特异性结合的物质，也叫免疫原(immunogen)。 An antigen is a molecule that stimulates an immune response. The word, antigen, originated from the notion that they can stimulate antibody generation. We now know that the immune system does not only consist of antibodies. The modern definition encompasses all substances that can be recognized by the adaptive immune system(i.e. T cell B cell). Tolerogen - An antigen that invokes a specific immune non-responsiveness due to its molecular form. If its molecular form is changed, a tolerogen can become an immunogen. Allergen - An allergen is a substance that causes the allergic reaction. The (detrimental) reaction may result after exposure via ingestion, inhalation, injection or contact with skin. Antigens can be classified in order of their origins Exogenous antigens Exogenous antigens are antigens that have entered the body from the outside, for example by inhalation, ingestion, or injection. By endocytosis or phagocytosis, these antigens are taken into the antigen-presenting cells (APCs) and processed into fragments. Endogenous antigens Endogenous antigens are antigens that have been generated within the cell, as a result of normal cell metabolism, or because of viral or intracellular bacterial infection. Autoantigens An autoantigen is usually a normal protein or complex of proteins (and sometimes DNA or RNA) that is recognized by the immune system of animals suffering from a specific autoimmune disease. These antigens should under normal conditions not be the target of the immune system, but due to mainly genetic and environmental factors the normal immunological tolerance for such an antigen has been lost in these animals. Tumor antigens Tumor antigens are those antigens that are presented by the