Human seminal plasma fosters CD4(+) regulatory T-cell phenotype and transforming growth factor-β1 expression.

Abstract

Semen mediates expansion of CD4(+) regulatory T cells (Treg) in the murine female reproductive tract. The impact of semen on Treg in humans, however, remains unclear. Using seminal plasma (SP) from 20 healthy donors, we investigated the impact of human semen on CD4(+) T-cell expression of CD127 and CD49d as well as CD4(+) CD127(low) CD49d(low) Treg proliferation, apoptosis, and intracellular expression of FoxP3, TGF-β1, and IL-10. SP reduced CD4(+) T-cell expression of CD127 and CD49d and increased the proportion of CD127(low) CD49d(low) Treg. This increase was non-proliferative, mediated in part via the conversion of CD4(+) helper T cells into FoxP3(-) but not FoxP3(+) Treg. Additionally, SP induced an increase in intracellular expression of the immunosuppressive cytokine TGF-β1 by the FoxP3(-) but not FoxP3(+) Treg. SP had no impact on Treg intracellular expression of IL-10. Human seminal plasma fosters the non-proliferative increase in the proportion and immunoregulatory activity of FoxP3(-) Treg.