In vitro effects of cyclosporine A and tacrolimus on regulatory T-cell proliferation and function.

Background: Liver transplantation is the treatment of end-stage liver diseases, including hepatitis C. Immunosuppression prevents graft rejection but seems to accelerate the recurrence of hepatitis C. Regulatory T cells (Tregs) may be beneficial in tolerance but deleterious in recurrent hepatitis C. We evaluated the effects of cyclosporine or tacrolimus, the principal immunosuppressive drugs, on Treg proliferation and function.
Methods: Human Tregs were isolated from healthy donors and cultured with cyclosporine, tacrolimus, or NIM811, a cyclosporine analog devoid of calcineurin-inhibiting activity. Treg proliferation and suppressive activity were assessed. The phenotype, cytokine production, and phosphorylation profile of nuclear factor of activated T cell of Tregs were also analyzed.
Results: Cyclosporine and tacrolimus both decreased Treg proliferation, but only low doses of cyclosporine reduced Treg activity, by inducing the production of interleukin 2 proinflammatory cytokines in these cells. Moreover, NIM811 also inhibited Treg activity. The phosphorylation of nuclear factor of activated T cell in Tregs was not altered by cyclosporine, suggesting that the effects of this drug are independent of the calcineurin pathway.
Conclusion: In summary, low doses of cyclosporine inhibit Treg activity, a finding that might explain the beneficial effect of this drug on hepatitis C recurrence. In contrast, by maintaining Treg activity, tacrolimus could be more helpful than cyclosporine in controlling rejection.