TGF-β1 induces differentiation of CD4~+CD25~-T cells into CD4~+CD25~+ reg ulatory T cells

Objective To investigate the capability of TGF-β1 to in duce the differentiation of CD4+CD25+ regulatory T cells and the mechanisms. Methods The nude Balb/c splenocytes pretreated with mitomycin as the stimulator were added to C57BL/6 T cells with or without TGF-β1 for a 6 -day culture. Four groups were e stablished: control group (0 ng/mL TGF-β1), low concentration group (0.1 ng/mL ) , middle concentration group (5 ng/mL), and high concentration group (10 ng/mL). At the end-point of culture, the percent of CD4+CD25+ T cells and the expr ession of Foxp3 mRNA were measured by FACS and RT-PCR, individually. Then CD4 +CD25-T cells were isolated by MACS and stimulated with alloantigen and TGF-β1. After a 6-day culture, CD4+CD25+ T cells were isolated and we measured the immuno suppr essive activity of these cells. Results The 5 ng/mL and 10 ng/m L TGF-β1 could increase the percent of CD4+CD25+ T cell and the expression of Foxp3 mRNA in T cells stimulated by alloantigen (P0.05). TGF-β1 indu ced CD4+CD25-T cells to convert to CD4+CD25+ T cells which could suppress the proliferation of lymph ocytes. Conclusion TGF-β1 induces CD4+CD25+ regulator T c ells from CD4+CD25-T cells which could express Foxp3 and suppress the proliferation of lymphocy tes.