DEFECTIVE EXPRESSION OF HLA-DR ANTIGENS (DR-Ag): ANOTHER CAUSE OF CHRONIC DIARRHEA

Abstract

Defective expression of DR-Ag on mononuclear cells has been recently described as a new cause of combined immuno-deficiency, with chronic diarrhea and failure to thrive as main features. We were interested in relating these symptoms with an eventual defect of DR-Ag expression on enterocyte membranes, in 17 patients. 15 had diarrhea, starting between 1 and 6 months in 8, later on in 7, becoming chronic afterwards in all cases. Documented malabsorption was demonstrated in only 4. Candidiosis was noted in 16 and cryptosporidiosis in 3. Intestinal biopsies were performed in 10 patients : villous atrophy was partial in 8, subtotal in 2; intestinal IgA plasmocytes were absent in 4, strongly decreased in 3 out of 7. In 5 patients cryostat sections were incubated with various monoclonal antibodies directed against DR-Ag and lymphocyte subpopulations. In contrast to controls and coeliac patients, no enterocyte staining was visible either in the crypts or the villi. In 4 patients a strong epithelium and lamina propria infiltration of cytotoxic/suppressor lymphocytes was noted. In conclusion, chronic diarrhea, nearly constant in this disease, might be related more often to the near complete lack of immunological reactivity towards exogenous antigens than to the intestinal lesions observed. It is remarkable that the latter occured even though enterocytes did not express DR-Ag.