Differences in Type 1 and Type 2 intracytoplasmic cytokines, detected by flow cytometry, according to immunosuppression (cyclosporine A vs. tacrolimus) in stable renal allograft recipients

Recent multicenter, randomized clinical trials have shown that in renal tra nsplant patients tacrolimus (FK506) was more efficient than cyclosporine A (CsA) at preventing acute rejection. In older to try and evaluate whether t his difference was related to a different br vivo T-cell suppression we ass essed, in a prospective study, the frequencies of interleukin (IL)-2-, IL-4 -, IL-5-, IL-6-, IL-10-, interferon-gamma (IFN-gamma)- and double-positive IL-2/IFN-gamma-producing whole T cells, CD4 + and CD8 + T-cell subsets by m eans of cytokine flow cytometry. This was performed after in vitro stimulat ion of peripheral blood mononuclear cells (PBMCs) with phorbol myristate ac etate (PMA) and ionomycin, in the presence of monensin, in 14 healthy volun teers (controls) and in 14 renal transplant patients. The immunosuppression of the latter was based either on CsA (n = 7) or on FK506 (n = 7). Cytokin e-expressing T-cell frequencies were assessed immediately pretransplantatio n (D0), and subsequently 3 months (M3) and 6 months (M6) afterwards in fast ing patients prior to the morning intake of the immunosuppressive drug. We found that at D0 the frequencies of IL-2-(22 +/- 2% vs. 22.2 +/- 2%), IFN-g amma-(26 +/- 3% vs. 29 +/- 3.4%) and IL-4-(0.8 +/- 0.2% vs. 1.4 +/- 0.2%)-e xpressing T lymphocytes were not significantly different between the contro ls and the patients, respectively. Conversely, the frequency of IL-2/IFN-ga mma double positive cells was higher in the latter (9.3 +/- 1.6%) than in t he controls (5.6 +/- 0.8); p = 0.06. Finally, on D0 the frequencies of IL-5 -, IL-6-, and IL-10-producing T lymphocytes were lower than 1% in both grou ps, as well as after grafting, i.e. on M3 and M6. As compared to baseline ( D0): (a) chronic immunosuppression significantly decreased the frequencies of IL-2-, IL-4- and IL-2/IFN-gamma-expressing T cells, whereas those of IFN -gamma, IL-5, IL-6, and IL-10 were not significantly affected; (b) the freq uencies of cytokine-expressing T cells were not statistically different bet ween M3 and M6; (c) the decrease in the frequencies of IL-2- and IL-2/IFN-g amma-expressing T cells affected CD4 + and CD8 + cells equally; (d) there w as a marginal decrease in the frequency of IFN-gamma-expressing cells only in the CD4 + subset but not in the CD8 population; and (e) for CsA, but not for FK506, the frequency of the IL-2-expressing T cells was negatively cor related with the whole blood trough levels. When we compared the frequencie s of cytokine-expressing cells in FK506- and CsA-treated patients, we found that the frequency of IL-2-expressing T cells was significantly lower with FK506 (10.9 +/- 1.6%) than with CsA (16.3 +/- 1.8%; p = 0.03), whereas the frequencies of the other cytokine-expressing cells were not statistically different between the two groups. In conclusion, our study clearly demonstr ated that studied ex vivo, FK506 and CsA decrease the frequencies of cells expressing IL-2, IL-4 and IL-2/IFN-gamma in vivo but do not affect those ex pressing IFN-gamma. Meanwhile, the frequency of IL-2-producing T cells was more affected with FK506 than with CsA and was negatively correlated with t he CsA trough level. Finally, our results regarding IL-2 might explain to s ome extent the higher efficiency of FK506 in vivo than CsA.