INDUCTION OF MHC CLASS-II GENE-PRODUCTS IN RAT INTESTINAL EPITHELIUM DURING GRAFT-VERSUS-HOST DISEASE AND EFFECTS ON THE IMMUNE FUNCTION OF THE EPITHELIUM

The induction of major histocompatibility complex (MHC) class II expression in the epithelium of the small intestine of the rat during graft-versus-host disease (GVHD) and the effect of this process on the capacity of isolated epithelial cells to present antigen has been investigated. By immunohistology, increased class II (I-A) was noted in lamina propria cells and villus epithelium and de novo expression in crypt epithelium by Day 7 after transfer of parental spleen cells into irradiated hybrid rats. This increased expression reached a maximum by Day 9 or 10. The kinetics of induction of I-E products paralleled those of I-A in villus epithelium, but I-E was not seen in crypt epithelium. Direct radioimmunoassay of class II in isolated villus and crypt epithelial cells revealed a minor peak of class II, particularly in villus cells, very soon after cell transfer which waned and then increased to a second peak at Days 7-9. Assay of presentation of ovalbumin by isolated enterocytes to primed T cells at the peak of class II induction showed that increased class II expression by villus cells mediated enhanced antigen-presenting activity, whereas increases in crypt cell class II did not enable these cells to present ovalbumin.