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Humoral Immunity - cell proliferates and differentiates The...

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Humoral Immunity The second half of acquired immunity results in the production and release of antibodies. Secreted antibodies are made by mature and differentiated B-lymphocytes. After activation and proliferation , B-lymphocytes differentiate into either plasma cells or memory B-cells. It is the plasma cells that secrete antibodies into the circulatory system to target and destroy invading antigens. In contrast to T-lymphocytes which recognize infected or cancerous host cells (because the infected cells display bacterial, viral or mutated proteins on their surface), virgin B-lymphocytes bind to an antigen that is specifically recognized by its unique receptors and then endocytose the B-cell receptor-antigen complex. The antigen is digested and displayed on the surface of the B- lymphocyte and the B-cell is briefly an APC . Helper T-cells stimulate the APC/B-cell and the B-
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Unformatted text preview: cell proliferates and differentiates. The resulting cells are clones of the original B-cell and therefore recognize the original antigen. The majority of B-lymphocytes differentiate into plasma cells which secrete antibodies that are specific to the activating antigen; thus the antibodies produced target that antigen. Some differentiated B-cells become memory cells which aggressively and rapidly target for destruction the same antigen if exposure occurs again. (See Figure 7) Figure 7 Antibodies Antibodies bind to the antigen and 1) neutralize the antigen by blocking the pathogenic region of the antigen; 2) "tag" the antigen for destruction by complement protein binding (complement fixation); 3) "tag" the antigen for destruction by phagocytosis; or 4) agglutinate the antigen and immobilize them until phagocytosis....
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