Objective To detect if Fas is expressed in human renal interstitial fibroblasts (hRIFs) and apoptosis of hRIFs can be induced by specific anti-fas antibody. Methods hRIFs were cultured from isolated papillae of human kidney, and identified by morphologic examination, assay of antigenic components and culture in D-valine selective medium. Fas expression in normal hRIFs was detected by RT-PCR and immunocytochemistry staining. After hRIFs were incubated with interferon gamma (gamma -IFN 500 U/ml, 1000 U/ml, 1500 U/ml and 2000 U/ml, respectively) for 48 hours, Fas expression was determined by Northern blot, Western blot and flow cytometry. hRIFs pre-stimulated with gamma -IFN (500 U/ml, 48 hours) were incubated with anti-fas antibody (IgM, 0.5 mug/ml) for 12 hours. And apoptosis was identified by morphologic examination, DNA ladder assay and flow cytometry. Results The cultured hRIFs showed a shuttle-like shape and were positively stained by labeled antivimentin antibody but negatively stained by anti-epithelial membrane antibody. They could not grow in the D-valine selective medium and died partly in a week. Fas mRNA and protein were expressed in normal hRIFs and markedly upregulated by stimulation with gamma -IFN. Apoptosis in gamma -IFN pre-stimulated hRIFs was induced by anti-fas antibody, showing cell nuclear shrinkage and condensation in morphologic feature, internucleosomal DNA fragmentation in DNA ladder assay and a pick of hypo-diploid nuclei by flow cytometry. Conclusion Fas is normally expressed in hRIFs and can be markedly upregulated by gamma -IFN. Anti-Fas antibodies can induce apoptosis of hRIFs pre-stimulated with gamma -IFN.