O agglutinin ( )n. An agglutinin that reacts with, and is formed as the result of stimulation by, the relatively thermostable antigens present in the cell bodies of microorganisms. |
agglutinin
any substance causing agglutination (clumping together) of cells, particularly a specific antibody formed in the blood in response to an invading agent. Such agglutinating antibodies (see immunoglobulin) function as part of the immune mechanism of the body. When the invading agents that bring about the production of agglutinins are bacteria, the agglutinins produced bring about agglutination of the bacterial cells both in vivo and in vitro.
Erythrocytes also may be agglutinated by agglutinins that are naturally present in the blood, such as the presence of anti A antibody in humans with the blood group B erythrocytes, or such agglutinins may also be formed in response to the entrance of noncompatible blood cells into the bloodstream. A transfusion reaction is an example of the result of agglutination of blood cells brought about by agglutinins present in the recipient's blood.
cold agglutinin
antibody that acts only at low temperature.
cold agglutinin disease
an autoimmune disease in which erythrocyte autoantibodies, usually IgM, are most active at temperatures below 98.6°F (37°C). Agglutination occurs in capillaries of the extremities (tail, ears, nose and feet), particularly on exposure to cold, resulting in tissue necrosis in those areas. Hemolytic anemia is a variable feature.
group agglutinin
antibody made against a particular organism. One that has a specific action on certain organisms, but will agglutinate other, usually related species as well.
H agglutinin
one that is specific for flagellar antigens of bacteria.
immune agglutinin
a specific antibody found in the blood after recovery from the disease or injection of the microorganism.
incomplete agglutinin
antibody that at appropriate concentrations fails to agglutinate the homologous antigen for steric reasons.
normal agglutinin
a specific antibody found in the blood of an animal or of humans that has had no known exposure to the antigen with which it combines; these may be natural antibodies such as those directed against A and B blood group antigens in humans or cross-reacting antibodies produced after infection with a related microorganism.
O agglutinin
antibody specific for somatic or cell wall antigens of a bacterium.
partial agglutinin
antibody which agglutinates organisms closely related to the specific antigen, but at a lower dilution.
warm agglutinin
an incomplete antibody that sensitizes and reacts optimally with erythrocytes at 98.6°F (37°C).
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