Secretory immunoglobulin deficiency in a family with inflammatory bowel disease.

A family with 4 of 10 first-degree relatives affected with inflammatory bowel disease (IBD) was studied to determine whether any distinct immunological abnormalities occur in the affected members, as compared with unaffected members of the family, normal controls, and other unrelated patients with IBD. Red cell blood type and HL-A phenotypes did not distinguish between healthy and affected members, although HL-A2, 32, B27, and B12 were the predominant haplotypes in members with IBD. There was no significant difference between the two groups in the lymphocyte subpopulation counts of T cells, B cells, and cells carrying Fc or complement receptors. The in vitro mitogen response, however, to phytohemagglutinin and pokeweed mitogen were depressed in the affected members. Serum IgA and C3 levels were significantly elevated in members with IBD compared to healthy subjects with values of 232 +/- 69 (mean +/- SD) versus 148 +/- 29 mg per dl for IgA (P less than 0.05) and 173 +/- 32 versus 115 +/- 22 mg per dl for C3 (P less than 0.025), respectively. Plasma and, to a lesser extent, peripheral lymphocytes from 2 affected members who were tested were cytotoxic to allogeneic colonic epithelial cells. Salivary IgA was normal in the affected family members and unrelated patients with IBD. However, the free secretory component of salivary IgA was absent or markedly depressed in family members, as well as in unrelated patients with ulcerative colitis. This deficiency of the secretory immune system appears to characterize more frequently ulcerative colitis than Crohn's disease and may compromise mucosal host defenses in IBD.