Accumulation of IL-17-Positive Cells in Decidua of Inevitable Abortion Cases

Th17 cells, a new subset of helper T cells, have been focused on as a producer pro-inflammatory cytokines. It is, however, still unknown how Th17 cells affect pregnancy outcome. We investigated the expression of IL-17-producing cells in human spontaneous abortion.Method of study IL-17 expression was analyzed in decidual tissues among normal pregnancy, missed abortion, and inevitable abortion cases by immunohistochemistry and flow cytometry.Results IL-17⁺ cells were accumulated in decidua and were detected in decidual CD4⁺ T cells and few decidual CD8⁺ T cells in spontaneous abortion cases. The number of decidual IL-17⁺ cells in inevitable abortion cases involving active genital bleeding was significantly higher than that in normal pregnancy cases (P < 0.05). On the other hand, there were no significant differences in the numbers of decidual IL-17⁺ cells between missed abortion cases and normal pregnancy subjects. Furthermore, the number of IL-17⁺ cells was positively correlated with the number of neutrophils in spontaneous abortion cases.Conclusion IL-17⁺ cells might be involved in the induction of inflammation in the late stage of abortion, but not in the early stage of abortion.