T cells which produce interleukin (IL)-17 are involved in chronic inflammatory processes and regulatory T (Treg) cells are possibly the most important immune regulators. We aimed to investigate peripheral blood IL-17⁺ T and Foxp3⁺ Treg cells in women with idiopathic recurrent pregnancy loss (RPL).

The study design is a cross-sectional evaluation of Th1, Th2, IL-17⁺ T and Treg cells in women with idiopathic RPL (n = 42) and age-matched parous controls (n = 24). Flow cytometric analysis was performed to measure IL-17⁺ T and Foxp3⁺ Treg cells, and ratios of Th1/Th2 cells using anti-IL-17A and anti-Foxp3 antibodies, and monoclonal antibodies to tumor necrosis factor (TNF)-α, interferon (IFN)-γ and IL-10. Student's t-test and partial correlations were applied for statistical analysis.

TNF-α-/IL-10-producing CD3⁺CD4⁺ T cell ratio was higher in women with RPL than controls (P = 0.048). Levels of IL-17⁺ T cells (P = 0.021) and the IL-17⁺ T/CD4⁺Foxp3⁺ Treg cell ratio (P = 0.001) were increased, whereas Foxp3⁺ (P = 0.035), Foxp3^low (P = 0.032) and CD4⁺Foxp3⁺ T cell (P = 0.037) levels were decreased in women with RPL, compared with controls. Levels of IL-17⁺ T cells were correlated with TNF-α-producing CD3⁺CD4⁺ T cells (r = 0.269, P = 0.033), and with ratios of TNF-α/IL-10 (r = 0.276, P = 0.027) and IFN-γ/IL-10 (r = 0.266, P = 0.035)-producing CD3⁺CD4⁺ cells. Furthermore, the ratio of IL-17⁺ T cells to CD4⁺Foxp3⁺ Treg cells showed a positive correlation with TNF-α-producing CD3⁺CD4⁺ T cells (P = 0.047) and IFN-γ-producing CD3⁺CD4⁺ T cells (P = 0.048) as well as a ratio of IFN-γ/IL-10-producing CD3⁺CD4⁺ T cells (P = 0.037).

Enhanced pro-inflammatory immune responses with suppressed immune regulation may be an important immune mechanism involved in RPL.