Relationship of HLA-DR expression to rejection and mononuclear cell infiltration in renal allograft biopsies.

Research on renal biopsies has shown that HLA class I antigens are distributed throughout the renal parenchyma, but that the distribution of HLA-DR varies greatly. We investigated HLA-DR expression in biopsies of 90 renal transplants, and also semiquantitatively assessed the proportions of CD68-, CD3-, and HLA-DR-positive infiltrating cells by immunohistochemistry. The relationships between tubular DR expression and interstitial lymphocyte and macrophage infiltration were examined. Forty of the biopsies showed acute rejection (AR), 33 showed chronic rejection (CR), 10 showed suspected rejection (SR), and 7 showed no evidence of rejection (NR). HLA-DR expression was noted in 35/40 (87.5%) of the AR cases, 22/33 (66.6%) of the CR cases, and 6/10 (60%) of the SR cases. Only 1 (14.3%) of the NR cases exhibited HLA-DR antigen expression in the renal tubules. The proportions of lymphocyte and macrophage infiltration observed in the interstitium were significantly correlated with tubular DR expression in all cases (p<0.01). At 6 months after biopsy was done, 24/35 (68.6%) of the AR patients with tubular DR expression had showed second episode of rejection or showed deteriorated renal function. The remaining 11 AR cases with tubular DR expression had stable renal function at this stage. The cases that had no significant tubular DR expression had no problems with rejection or functional deterioration. These findings are consistent with the theory that expression of HLA-DR antigens on renal tubular cells may be a marker of rejection and poor graft outcome.