Immunological advantages of everolimus versus cyclosporin A in liver-transplanted recipients, as revealed by polychromatic flow cytometry.

Several immunosuppressive drugs with different mechanisms of action are available to inhibit organ rejection after transplant. We analyzed different phenotypic and functional immunological parameters in liver-transplanted patients who received cyclosporin A (CsA) or Everolimus (Evr). In peripheral blood mononuclear cells (PBMC) from 29 subjects receiving a liver transplant and treated with two different immunosuppressive regimens, we analyzed T cell activation and differentiation, regulatory T cells (Tregs) and Tregs expressing homing receptors such as the chemokine receptor CXCR3. T cell polyfunctionality was studied by stimulating cells with the superantigen staphylococcal enterotoxin B (SEB), and measuring the simultaneous production of interleukin (IL)-2 and interferon (IFN)-γ, along with the expression of a marker of cytotoxicity such as CD107a. The analyses were performed by polychromatic flow cytometry before transplantation, and at different time points, up to 220 days after transplant. Patients taking Evr had a higher percentage of total CD4⁺ and naïve CD4⁺ T cells than those treated with CsA; the percentage of CD8⁺ T cells was lower, but the frequency of naïve CD8⁺ T cells higher. Patients taking Evr showed a significantly higher percentage of Tregs, and Tregs expressing CXCR3. After stimulation with SEB, CD8⁺ T cells from Evr-treated patients displayed a lower total response, and less IFN-γ producing cells. The effects on the immune system, such as the preservation of the naïve T cell pool and the expansion of Tregs (that are extremely useful in inhibiting organ rejection), along with the higher tolerability of Evr, suggest that this drug can be safely used after liver transplantation, and likely offers immunological advantages.