Berberine (BB) is a protoberberine alkaloid derived from various representatives of the Berberidaceae family. Although used as a therapeutic agent, it has not been applied in the treatment of immune-mediated disorders. In the present study, BB was administered at a daily dose of 10 mg/kg for 3 consecutive days before the induction of tubulointerstitial nephritis (TIN) by injection of bovine tubular basement membrane (TBM) antigen in BALB/c mice. The animals were investigated 2 months after TBM inoculation. The intensity of pathological injuries in animals with TIN+BB decreased significantly, an effect that correlated with the improvement of renal function. Flow cytometric analysis of peripheral blood cells showed that BB caused a decrease in the number of CD3(+), CD4(+), CD8(+), and sIg(+) lymphocytes in comparison with TIN mice. The same tendency was noticed in the lymphocytes from kidney infiltrates of treated animals. The control animals treated only with BB showed a decrease in the number of CD3(+), CD4(+), CD8(+) T-lymphocytes in comparison with control nontreated mice. Our results, thus, indicate that BB has an immunosuppressive effect in the TIN model, which is an analogue of various human kidney autoimmune diseases.