Inhibitory Effects of Cyclosporine on Human Regulatory T Cells In Vitro

Abstract

Background Inevitable hepatitis C virus (HCV) recurrence after liver transplantation is a major barrier to the survival of a transplanted liver. It may be promoted by immunosuppression and the emergence of CD4 +CD25 + regulatory T cells (Treg). Treg cells can mediate the induction and maintenance of immunological self-tolerance as well as transplant tolerance. We investigated the effects of cyclosporine (CsA), a widely used immunosuppressive agent, on human CD4 +CD25 + Treg cells. Methods Human CD4 +CD25 + cells isolated from healthy donors were cultured in the presence of 40 or 400 ng/mL CsA. The suppressive activity of Treg was assessed in mixed leukocyte reactions (MLR) using CD25 + and autologous activated peripheral blood mononuclear cells (PBMC). Phenotype analysis (flow cytometric, Q-PCR) and cytokine production (ELISA) of Treg cells were then performed on cultures. Results CsA (40 or 400 ng/mL) inhibited the proliferative capacity of PBMC and CD4 +CD25 + Treg in a dose-dependent manner. Interestingly, addition of 40 ng/mL CsA in MLR impaired the suppressive activity of CD4 +CD25 + cells, whereas a higher dose of CsA had no effect on Treg function. It appears that a therapeutic dose of CsA (40 ng/mL) did not change the phenotype of CD4 +CD25 + T cells, but altered Treg activity by switching the regulatory to an inflammatory cytokine profile. Conclusion CsA significantly impaired the function of CD4 +CD25 + Treg cells by inducing interleukin-2 (IL-2) and interferon-γ (IFN-γ) secretion. The present studies suggested that CsA may block the induction of immune tolerance and decrease the risk of hepatitis C recurrence.