platelet agglutinin


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agglutinin

 [ah-gloo´tĭ-nin]
any substance causing agglutination (clumping together) of cells, particularly a specific antibody formed in the blood in response to the presence of an invading agent. Agglutinins are proteins (immunoglobulins) and 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.

Erythrocytes also may agglutinate when agglutinins are 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 produced in the recipient's blood in response to incompatible or foreign cells (the donor's blood). Anti-Rh agglutinins are produced in cases of Rh incompatibility and can result in a condition known as erythroblastosis fetalis when the maternal blood is Rh negative and the fetal blood is Rh positive. (See also rh factor.)
cold agglutinin antibody that agglutinates erythrocytes or bacteria more efficiently at temperatures below 37°C than at 37°C.
group agglutinin one that has a specific action on certain organisms, but will agglutinate other species as well.
H agglutinin one that is specific for flagellar antigens of the motile strain of an organism.
immune agglutinin a specific agglutinin found in the blood after recovery from the disease or injection of the microorganism.
incomplete agglutinin one that at appropriate concentrations fails to agglutinate the homologous antigen.
O agglutinin one specific for somatic antigens of a microorganism.
platelet agglutinin an antibody capable of agglutinating platelets; these may be associated with a variety of disorders, with and without frank thrombocytopenia.
warm agglutinin an incomplete antibody that sensitizes and reacts optimally with erythrocytes at 37°C.

platelet agglutinin

(1) Platelet antibody. 
(2) Platelet agglutinin (in current use).
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