Studies on IgA class circulatory red cell antibodies--II. Properties of IgA class anti-A,anti-B.

The properties of IgA class red cell alloantibodies were determined using an anti-A,anti-B preparation confirmed to be free from IgG and IgM. The following characteristics were found: a thermal optimum of 37 degrees C; saline agglutination enhanced by anti-human IgA; activity substantially unchanged after 1 year's storage at 4 degrees C, but reduced by papain and destroyed by pepsin and by reduction and alkylation; neutralization by AB blood group substance; an inability to activate complement; and a distinctive pattern of apparent molecular sizes (reflecting dimeric and monomeric forms and complexes with serum proteins) which was significantly altered by the action of enzymes and by reduction and alkylation.