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Induction of Fas-mediated apoptosis in a human renal epithelial cell line by interferon-gamma: involvement of Fas-mediated apoptosis in acute renal rejection.

To examine the role of the Fas ligand/Fas (FasL/Fas) system and apoptosis in renal allograft rejection, we analyzed FasL/Fas expression and apoptosis in 63 renal allograft biopsy specimens obtained from 56 renal transplant recipients in Tokyo, Japan. Sixteen biopsy specimens were diagnosed (Banff criteria) as acute rejection (AR), 17 as AR plus chronic rejection, 10 as borderline stages, and 20 as no rejection (NR). Immunohistochemically, Fas antigen was highly expressed in the renal tubular epithelium in tissues from patients with rejection. The mean number of Fas-positive tubular epithelium was significantly higher in biopsy specimens with AR than in those with NR, but FasL expression was highly expressed in infiltrating lymphocytes in the interstitium of allografts with cellular rejection. The mean number of FasL-positive infiltrating lymphocytes was significantly higher in specimens with AR than in those with NR or borderline stages. For detection of apoptotic cells, the specimens were subjected to terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling, which showed that the mean number of tubular epithelial cells positive for this labeling was highest for the specimens with AR, the number being significantly higher than in those with AR plus chronic rejection or with NR. Thus, Fas expression on epithelial cells might actively trigger their apoptosis by the interaction between Fas and FasL. Studies of human normal renal-derived cell lines (RPTEC 2601 [epithelial] and NHMC 5155 [mesangial]) showed that both constitutively expressed Fas (but not FasL) mRNA. After pretreatment with interferon-gamma, Fas-induced apoptosis was observed in the RPTEC 2601 line, but without interferon-gamma pretreatment, anti-Fas-mediated apoptosis was not seen. Under identical conditions, the NHMC 5155 line was resistant to anti-Fas-mediated apoptosis regardless of interferon-gamma pretreatment. This suggested that AR might be associated with increased apoptosis in the renal tubular epithelial cells mediated by the Fas/FasL system.