Small intestinal villous enterocytes express Class II molecules whereas crypt cells do not. The role of such molecules in the gut is unknown but it has been suggested that they may be involved in maintaining tolerance to oral antigens. In some children with IPD, circulating EcAbs are present together with other autoimmune manifestations. Jejunal biopsies from 9 children with IPD, EcAbs and an enteropathy were compared with histologically normal jejunum from 9 controls. We studied HLA Class I and II molecule expression in the enterocyte epithelium by immunofluorescence. HLA Class I products were normally expressed in the jejunal epithelium of IPD patients. Class II (DR complex) expression in controls was restricted to upper villous enterocytes. In 6/9 patients with IPD and EcAbs (titres ⋝1:64) aberrant expression of DR molecules was seen in crypt enterocytes. It can be suggested that by analogy with a similar phenomenon detected in glands from patients with classical autoimmune diseases, DR+ve crypt enterocytes would be able to act as Ag presenting cells, bypassing macrophage requirement. In the other 3 patients with EcAbs (titres ⋜1:8) a decreased reactivity was seen in villous enterocytes. In all 9 patients numerous DR+ve cells were present in the lamina propria compared to controls. We postulate that aberrant MHC molecule expression in the small intestine might reflect loss of tolerance to luminal antigen which could lead to autoimnune disease.
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Mirakian, R., Richardson, C., Walker-Smith, J. et al. 72. HLA D/DR Ag EXPRESSION IN THE JEJUNUM OF CHILDREN WITH IDIOPATHIC PROTRACTED DIARRHOEA (IPD) AND CIRCULATING ENTEROCYTE ANTIBODIES (EcAb). Pediatr Res 22, 108 (1987) doi:10.1203/00006450-198707000-00093