cold agglutinin

agglutinin /ag·glu·ti·nin/ (ah-gloo´tĭ-nin)

1. antibody which aggregates a particulate antigen, e.g., bacteria, following combination with the homologous antigen.

2. any substance other than antibody, e.g., lectin, that is capable of agglutinating particles.

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anti-Rh agglutinin  an agglutinin not normally present in human plasma, which may be produced in Rh− mothers carrying an Rh+ fetus or after transfusion of Rh+ blood into an Rh− patient.

chief agglutinin  major a.

cold agglutinin  one that acts only at relatively low temperatures (0°–20° C).

group agglutinin  one that has a specific action on a particular group of microorganisms.

H agglutinin  one that is specific for flagellar antigens of the motile strain of a microorganism.

immune agglutinin  any agglutinating antibody.

incomplete agglutinin  one that at appropriate concentrations fails to agglutinate the homologous antigen.

leukocyte agglutinin  one that is directed against neutrophilic and other leukocytes.

major agglutinin  that present at highest titer in an antiserum.

minor agglutinin , partial agglutinin one present in agglutinative serum which acts on organisms and cells that are closely related to the specific antigen, but in a lower dilution.

warm agglutinin  an agglutinin more reactive at 37° C than at lower temperatures.

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cold agglutinin

n.

An agglutinin associated with cold agglutination.

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cold agglutinin,

a nonspecific antibody, found on the surface of red blood cells in certain diseases, that may cause clumping of the cells at temperatures below 36° C and may cause hemolysis. The phenomenon does not occur at body temperature. Mycoplasma pneumonia, infectious mononucleosis, and many lymphoproliferative disorders are associated with cold agglutinins.

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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.

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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).