| Summary: | MicroRNA (miR)-155 is a critical player in both innate and adaptive immune responses. It can influence CD4(+) T cell lineage choice. To clarify the role of miR-155 in CD4(+) CD25(+) regulatory T (Treg)/T helper (Th)17 cell differentiation and function, as well as the mechanism involved, we performed gain-and loss-of-function analysis by transfection pre-miR-155 and anti-miR-155 into purified CD4(+) T cells. The results showed that miR-155 positively regulated both Treg and Th17 cell differentiation. It also induced the release of interleukin (IL)-17A by Th17 cells, but not the release of IL-10 and transforming growth factor (TGF)-β1 by Treg cells. Furthermore, we found that miR-155 reacted through regulating Janus kinase/signal transducer and activator of transcription (JAK/STAT) rather than TGF-β/mothers against decapentaplegic homolog (SMAD) signaling pathway in the process of Treg and Th17 cells differentiation. This may because suppressors of cytokine signaling (SOCS)1, the important negative regulator of JAK/STAT signaling pathway, was the direct target of miR-155 in this process, but SMAD2 and SMAD5 were not. Therefore, we demonstrated that miR-155 enhanced Treg and Th17 cells differentiation and IL-17A production by targeting SOCS1.
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