Healthy blood donors with selective absence of immunoglobulin A: prevention of anaphylactic transfusion reactions caused by antibodies to IgA.

Gel diffusion analysis of sera from 73,569 healthy volunteer blood donors revealed apparent lack of IgA in 113 (1:650) samples, all with normal levels of IgG and IgM. Of these, 30 sera had low levels of IgA, while the remaining 83 had no IgA detectable by a more sensitive hemagglutination inhibition assay. The frequency of absent IgA (algA) was 1:886. High-titer anti-IgA was detected in the sera of 13 algA donors; only two had any known history of parenteral injection of IgA. Passive transfusion of high-titer anti-IgA in the units of blood elicited no clinical reaction in the recipients. Precipitating antibodies to ruminant IgM were present in 14 of the 83 donors. The incidence of hepatitis B surface antigen (HB-sAg), anti-HB-sAG, and antinuclear antibodies was the same in IgA-deficient and control sera. The algA donors form a unique resource for blood components for the clinical management of patients with anapylactic reactions caused by anti-IgA.