The interleukin-10 inducing effect of transforming growth factor-β on human naive CD4⁺ T cells from cord blood is restricted to the T _H1 subset

Transforming growth factor (TGF-β) seems to play a role in the regulation of immune responses, mainly by its suppressive function towards cells of the immune system. However, both in mice and human, conflicting data are published on the capacity of TGF-β to induce interleukin (IL)-10 secretion in both naive and skewed T cell populations. Our aim was to test the IL-10-inducing capacity of TGF-β in both naive and skewed cord blood mononuclear cells (CBMCs) and elucidate the mechanism by which TGF-β exerts its effect. Therefore, naive CBMCs and CBMCs during skewing under T helper 1 (Th1) and Th2 polarizing conditions were stimulated with CD3 and/or CD28 in the presence or absence of TGF-β. Proliferation, cytokine production and mRNA expression of transcription factors was measured. TGF-β enhanced the IL-10 production in Th1 and naive cells only, and suppressed the T_H1 phenotype as demonstrated in cytokine levels and T-box expression in T cells (T-bet) expression. Interestingly, forkhead box p3 (Foxp3) expression tended to increase in both Th1 and Th2 cells. These data indicate that TGF-β can induce a regulatory phenotype in both naive and Th1-polarized cells derived from cord blood. The induction of IL-10 was not observed in Th2-polarized phenotype, indicating that TGF-β might be especially of interest for immunomodulation in Th1 cells.