Weak anti-IgA antibodies with limited specificity and nonhemolytic transfusion reactions.

Anti-IgA antibodies were studied in sera from patients with nonhemolytic transfusion reactions for which no serological reason had been found. Of the 158 sera that were studied by passive hemagglutination assay using twelve IgA myeloma proteins, 4 samples had class-specific antibodies and 10 samples antibodies with limited specificity. Titers were 1:8 or less. 100 multitransfused hemophilia patients were studied with two IgA myeloma proteins. Four of the sera had anti-IgA antibodies. Normal blood donor sera reacted with IgA only when antigens were first either digested with pepsin or stored for several months as dilute solutions in refrigerator. The results emphasize the need for fresh IgA proteins of good quality when human anti-IgA antibodies are investigated.