cold 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.

cold ag·glu·ti·nin

an antibody that reacts more efficiently at temperatures lower than 37°C.

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.

cold agglutinin

Any of the IgM antibodies that agglutinate at <32ºC and react with blood groups I and i, which are often present in atypical pneumonia caused by Mycoplasma pneumoniae. Cold agglutinins cause clumping of red cells when the extremities are cooled, causing Raynaud phenomenon.

Specimen
Serum.
 
Ref range
Titer < 32.
 
Method
RBC agglutination.

cold ag·glu·ti·nin

(kōld ă-glū'ti-nin)
An antibody that reacts more efficiently at temperatures below 37°C.

cold agglutinin

A substance found in blood serum that causes red blood cells to clump together (agglutination) if the blood is kept at low temperatures.

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).