EXPRESSION OF CLASS-II MAJOR HISTOCOMPATIBILITY COMPLEX-MOLECULES IN RENAL TUBULAR EPITHELIAL-CELLS OF CANINE KIDNEYS AFFECTED WITH TUBULOINTERSTITIAL NEPHRITIS

Class II major histocompatibility complex (MHC) products are important molecules on various antigen-presenting cells and induce a T cell-spe cific immune response. The distribution of class II MHC molecules in t he normal canine kidney and kidneys of dogs with tubulointerstitial ne phritis was investigated by using a sensitive immunocytochemical metho d. In the normal canine kidney, class II MHC molecules were detected i n interstitial 'dendritic' cells. In cases of tubulointerstitial nephr itis, however, the expression of class II MHC molecules extended to ot her renal elements such as the epithelial cells of cortical and medull ary tubules and, in some cases, the endothelial cells of peritubular c apillaries. The tubular expression of class II MHC molecules was enhan ced in dogs with higher levels of proteinuria. The results suggest tha t heavy proteinuria may be one triggering factor in canine tubulointer stitial damage, probably mediated by the reabsorption of filtered cyto kines and immunogenic peptides which induce tubular epithelial cells t o behave as immune accessory cells.