Deficiency of decidual IL-10 in first trimester missed abortion: A lack of correlation with the decidual immune cell profile

Problem: To determine if first trimester missed abortion decidua is characterized by an altered immune cell profile and/or a modified interleukin (IL)-10 and interferon (IFN)-γ production pattern compared with decidua from elective termination. Method of study: Flow cytometry and immunohistochemistry techniques were used to determine the decidual immune cell phenotypic profile and production pattern of IL-10 and IFN-γ in cases of elective termination (n = 14) and missed abortion (n = 12). Results: Both groups had a similar proportion of CD56⁺ CD16^-, CD56⁺ CD16⁺, CD19⁺, CD3⁺, CD4⁺, CD8⁺, αβ T cells and γδ T cells. The majority of αβ and γδ positive T cells in both groups coexpressed the natural killer (NK) cell marker CD56, but lacked cell surface expression of CD3. Diminished decidual IL-10 staining was noted in 7/10 missed abortion cases compared with none of the elective termination cases (n = 12) (P = 0.007). A uniform decidual IFN-γ staining pattern was observed in both groups. Conclusion: Decreased IL-10 production coupled with a sustained IFN-γ presence noted in missed abortion compared with elective termination cases suggest that these cytokines may be important determinants in pregnancy outcome. In contrast, differences in the proportion of immune cells between both groups may not be a critical factor in early pregnancy loss. In normal pregnancy, decidual αβ and γδ positive T cells with reduced CD3 on their cell surface may be intrinsically restricted in T-cell receptor (TCR)-mediated activation.