CIRCULATING INTERLEUKIN-10-PRODUCING DENDRITIC CELLS ARE ASSOCIATED WITH HIGH INTERFERON-γ, IL-2, AND IL-3, AND LOW IL-10 IN PLASMA OF RENAL TRANSPLANT RECIPIENTS (2004)

P997 Aims: A domination of circulating plasmacytoid dendritic cells type 2 (DC2) late posttransplant was reported to be associated with good liver graft acceptance. In-vitro, both IL-10-producing myeloid and plasmacytoid DC were shown to polarize T helper cells (Th) into Th2 lymphocytes. Both exogenous and endogenous IL-10 affects the maturation of bone-marrow-derived dendritic cells in vitro and strongly influences T cell priming in vivo. Immature DC exposed to IL-10 for at least 2 days of culture showed a strongly reduced capacity to elicit a CD4+ T cell response in allogeneic MLR and it was shown that IL-10 converts immature DC into tolerogenic antigen presenting cells. We investigated in symptom-free renal transplant recipients early and late posttransplant whether IL-10-producing DC (IL-10+ DC) and Th might be conditioned towards anergy by high plasma IL-10. Methods: Plasma levels of soluble interleukin-1 receptor antagonist (sIL-1RA), IL-2, sIL-2R, IL-3, IL-4, IL-6, sIL-6R, IL-10, tumor-necrosis-factor-α (TNF-α), transforming-growth-factor-β2 (TGF-β2), and interferon-γ (IFN-γ) were studied in 25 hospitalized renal transplant recipients without acute rejection or acute infection early (x±1SD: 11±7 days) posttransplant, and in 32 symptom-free outpatients late (x±1SD: 2762±2423 days) posttransplant using standard ELISA. Intracellular IL-12 and IL-10 content of CD11c+CD83+CD40+ DC was measured in freshly obtained whole blood using four-color fluorescence flow cytometry. Proportions of CD11c+CD83+CD40+IL-12+ and CD11c+CD83+CD40+IL-10+ DC were compared with plasma cytokine levels. Results: Plasma IFN-γ (p=0.003) and IL-2 (p=0.01) were positively, plasma IL-10 (p=0.01) negatively associated with the posttransplant day, and high plasma IFN-γ and low plasma IL-10 were associated with low daily dosages of cyclosporine (IFN-γ: p=0.009; IL-10: p=0.0001), methylprednisolone (IFN-γ: p=0.002; IL-10: p=0.001), and mycophenolate mofetil (IFN-γ: p=0.08; IL-10: p=0.005). Th2 cytokines were found to dominate early posttransplant whereas during maintenance immunosuppression late posttransplant Th1 cytokines were high. It seems that IL-10+ DC are induced independent of IL-10 plasma levels. Both IL-12+ DC and IL-10+ DC were associated with low plasma IL-10 (IL-12+ DC: p=0.01; IL-10+ DC: p=0.01) and high plasma IL-6 (IL-12+ DC: p=0.009; IL-10+ DC: p=0.001). In addition, IL-10+ DC were associated with high plasma levels of IL-3 (p=0.003), IFN-γ (p=0.01), and IL-2 (p=0.05). The data suggest that IL-10+ DC dominate late posttransplant in association with high Th1 plasma cytokines. Plasma levels of IFN-γ and IL-10 were independent of graft function and serum creatinine levels in these patients with good graft outcome. Mycophenolate mofetil seems to affect TGF-β2 plasma levels because high plasma TGF-β2 was associated with low dose mycophenolate mofetil (p=0.01). Conclusion: High proportions of IL-10+ DC in transplant recipients with good graft outcome are associated with high IFN-γ, IL-2, and IL-3, and low IL-10 plasma levels. Strong immunosuppression is associated with a domination of Th2 and lower maintenance immunosuppression with a domination of Th1 cytokines in the plasma. Obviously, plasma cytokine levels do not affect the induction of IL-10+ DC late posttransplant implying that DC and Th are not conditioned towards anergy by high plasma IL-10 in outpatients.