Immunohistochemical study of Ia antigen in the normal and diseased human kidney

The presence and distribution of Ia antigen in normal human kidneys and biopsy specimens from patients with renal disease were investigated by immunohistochemical techniques using two monoclonal antibodies to the nonpolymorphic determinants of human HLA-DR molecules. Ia antigen was found on the endothelium of glomerular and peritubular capillaries and of veins and vasa recta. Loss of endothelial staining was found in necrotic and sclerotic glomerular and tubulointerstitial lesions. Staining or decreased staining was also not found in the severe proliferative nephritis of systemic lupus erythematosus although endothelial cells could still be identified upon light microscopic examination of the same biopsy specimen. Resting and proliferating cells in mesangial areas did not stain with anti-Ia antibody and extracapillary proliferating cells did not express Ia antigen except for occasional cells in anti-GBM crescentic glomerulonephritis, suggesting that Ia-bearing cells are not involved in mesangial and most extracapillary proliferations in human glomerulonephritis. All clustered mononuclear cells infiltrating the renal interstitium stained with anti-Ia antibody regardless of the type of nephritis where infiltrates occurred.