Low-dose cyclosporine mediates donor hyporesponsiveness in a fully mismatched rat kidney transplant model

Tolerance induction protocols have been successfully tested in animal models, yet their compatibility with immunosuppressive drugs remains to be fully elucidated. Our own previous data have indicated that cyclosporine A (CsA) affects the balance of effector and regulatory mechanisms with low-dose CsA doses promoting hyporesponsiveness. Here, we present a fully mismatched rat kidney model in which low-dose CsA treatment induces donor hyporesponsiveness to secondary renal allografts. Lewis recipients of DA kidney grafts received low, medium or high doses of CsA × 10 days. By 30 days, the primary transplant was removed and a second transplant of donor origin was engrafted. Following low-dose CsA, but not high-dose CsA treatment of the primary recipient, secondary transplants were accepted long-term in the absence of immunosuppression. Regulatory T-cell function was unimpaired and independent of the CyA dosage. Of note, low-dose CsA significantly reduced alloantibody titers in primary recipients. Adoptive transfer of graft infiltrating cells or splenocytes from hyporesponsive recipients supported long-term acceptance of donor kidney allografts. These results demonstrate a dose-dependent and transferable "pro-tolerogenic" effect of low-dose CsA treatment. This model is of clinical relevance to test the interference of CsA with tolerance induction in the absence of additional immunosuppression.