Selective absence of immunoglobulin A1 or A2 among blood donors and hospital patients.

A hemagglutination inhibition assay was developed for the determination of immunoglobulin A1 and A2 (IgA1 and IgA2) with subclass-specific rabbit antiserums. Among 93,020 apparently healthy blood donors, selective absence of IgA1 was found in six and that of IgA2 in 15, at a prevalence much higher than the absence of total IgA that was revealed by only one donor. Among 6800 hospital patients with various disorders, the absence of IgA1 was found in one with breast cancer and that of IgA2 in two with rheumatoid arthritis.