Estradiol-dependent perforin expression by human regulatory T-cells

P>Background CD4+CD25+FoxP3+ regulatory T-cells (nT(Reg)) have been shown to suppress immune responses to autoantigens and to other diverse antigens, this suppression is mainly mediated by a cell contact-dependent mechanism not yet fully defined. It has been reported that both human natural and induced T-Reg exert cytotoxic activity against autologous target cells, which suggests that the perforin/granzyme pathway may be a relevant candidate mechanism for the suppressive function of T-Reg. Previous reports have shown that oestradiol (E2) modulates T-Reg percentages and function. Methods We have evaluated in pregnant and non-pregnant subjects perforin intracellular expression in CD4+CD25+FoxP3+ regulatory T-cells by flow cytometry in whole blood, ex-vivo purified nT(Reg) and ex-vivo purified nT(Reg) after TCR and E2 stimulation. The expression of cellular degranulation markers was also phenotypically determined. Results We show that E2 expands T-Reg, enhances in vitro T-Reg function and induces a T-Reg phenotype in activated responder (CD4+CD25) T-cells, further increasing the expression of perforin on T-Reg than in vitro T-cell receptor activation alone. We found surface lysosomal-associated membrane glycoproteins (LAMP)-1and LAMP-2 expression by T-Reg, which is a sign of cell degranulation and therefore of cytotoxicity exerted by these cells. Conclusion Our data demonstrates the presence of functional T-Reg cytotoxic properties in biological systems and support the concept that E2 enhances the number and function of T-Reg suggesting the potential interaction between E2 and immunoregulatory mechanisms.