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An illustration that shows how antigens induce the immune system response by interacting with an antibody that matches the molecular structure of an antigen. In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. [1]
However, strictly speaking, immunogenicity refers to the ability of an antigen to induce an adaptive immune response. Thus an antigen might bind specifically to a T or B cell receptor, but not induce an adaptive immune response. If the antigen does induce a response, it is an 'immunogenic antigen', which is referred to as an immunogen.
In contrast, the B cell antigen-specific receptor is an antibody molecule on the B cell surface and recognizes native (unprocessed) antigen without any need for antigen processing. Such antigens may be large molecules found on the surfaces of pathogens, but can also be small haptens (such as penicillin) attached to carrier molecule. [60]
Each antibody recognizes a specific antigen unique to its target. By binding their specific antigens, antibodies can cause agglutination and precipitation of antibody-antigen products, prime for phagocytosis by macrophages and other cells, block viral receptors, and stimulate other immune responses, such as the complement pathway.
The antigens and antibodies combine by a process called agglutination. It is the fundamental reaction in the body by which the body is protected from complex foreign molecules, such as pathogens and their chemical toxins. In the blood, the antigens are specifically and with high affinity bound by antibodies to form an antigen-antibody complex.
The phagocytic cells of the immune system include macrophages, neutrophils, and dendritic cells. Phagocytosis of the hosts' own cells is common as part of regular tissue development and maintenance. When host cells die, either by apoptosis or by cell injury due to an infection, phagocytic cells are responsible for their removal from the ...
These antigens are almost universally present on human red cells, but their absence has been noted in some individuals and some have been associated with transfusion reactions or other problems. Finding compatible units for transfusion to a patient that lacks one of these antigens is a major challenge and some countries maintain rare donor ...
Antigen processing, or the cytosolic pathway, is an immunological process that prepares antigens for presentation to special cells of the immune system called T lymphocytes. It is considered to be a stage of antigen presentation pathways.
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