Clinical and immunologic features of selective IgA deficiency.

Selective absence of serum and secretory IgA is probably the most common form of human immunodeficiency. High frequencies of recurrent sinusitis, otitis media, pneumonia, and atopy were noted among a group of 75 such patients, all but 4 of whom were Caucasian. Seven instances of familial absence of IgA were detected among 106 relatives of 34 of the group; in 1 family 1 member from each of 3 successive generations was affected. Two IgA-deficient children were later found to have normal amounts of serum IgA. Despite their humoral deficit, B lymphocytes bearing surface IgA were detected in 9/9 IgA-deficient patients in immunofluorescence studies of their peripheral blood lymphocytes. Although in vitro lymphocyte responses to 2 putative T-cell mitogens and to allogenic cells were normal, results of spontaneous rosette formation studies with sheep erythrocytes raise the possibility of a lymphocyte subpopulation deficit in this condition.