2) Antibody-Mediated (Humoral) Immunity: B cells transform into plasma cells, which synthesize and secrete specific proteins called Antibodies or Immunoglobulins. A given antibody can bind to and inactivate a specific antigen. Works primarily against extracellular pathogens including viruses, bacteria, or fungi that are in body fluids outside cells. This type of immunity involves antibodies binding to antigens in body “humors” which are fluids as blood or lymph. When a particular antigen enters the body, there is only a small group of lymphocytes with the correct antigen receptors to respond to that antigen. This group includes a few helper T cells, cytotoxic T cells, and B cells. Depending on the location of where an antigen enters both types of adaptive immunity can be initiated.
Antigens and Antigen Receptors
Antigen means Antibody Generator
Antigens have 2 important characteristics:
Immunogenicity: is the ability to provoke an immune response by stimulating the production of specific antibodies, the proliferation of specific T cells, or both. Reactivity: is the ability of an antigen to react specifically with the antibodies or cells it provoked. Typically, just certain small parts of a large antigen molecule act as triggers for immune responses. These parts are called Epitopes. Antigens that get past the innate defenses generally follow one of three routes into lymphatic tissue: 1. Most antigens enter the blood stream (through an injured blood vessel) are trapped as they flow through the spleen. 2. Antigens that penetrate the skin, enter lymphatic vessels and lodge in lymph nodes. 3. Antigens that penetrate the mucous membranes are entrapped by mucosa-associated lymphatic tissue (MALT). Antigens are most often proteins. Nucleic acids, lipoproteins, glycoproteins, and certain large polysaccharides may act as antigens.
Generally, antigens are foreign substances; they are not usually part of body tissues. T cells MUST be able to recognize your own antigens ( self-recognition ) and they MUST lack reactivity to your
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