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.