Objective: To test the hypothesis that peripheral blood mononuclear cells in women with unexplained recurrent abortion (URA) produce T-helper 1 (TH1)-type cytokines in response to trophoblast antigens.
Design: Cohort study.
Setting: Medical center.
Participants: A total of 244 women with URA, 13 reproductively normal parous control women, and 10 men.
Main outcome measures: Supernatants from trophoblast-activated peripheral blood mononuclear cells from all participants were tested for toxic effects on mouse embryos and by enzyme-linked immunosorbent assay (ELISA) for interferon gamma (IFN-gamma). Supernatants from 20 URA patients with embryotoxic activity and IFN-gamma, 13 reproductively normal parous women, and 10 men were further tested by ELISA for other TH1-type cytokines (interleukin-2 [IL-2], tumor necrosis factor-beta [TNF-beta]), TH2-type cytokines (IL-4, IL-10), and TNF-alpha.
Results: Embryotoxic activity was detected in supernatants from 160 of 244 URA patients and in none of the controls. Interferon gamma was detected in supernatants from 125 of 244 URA patients and was significantly associated with embryotoxicity (121 of 160 supernatants with embryotoxicity vs four of 84 supernatants without embryotoxicity [P < .001]). Of 20 supernatants from patients chosen for further study, all were positive for TNF-alpha, 17 for TNF-beta, two for IL-10, and one for IL-4. No cytokines were detected in supernatants from unstimulated or red blood cell membrane-activated cells of women with URA. In contrast, trophoblast-activated lymphocyte supernatants from reproductively normal women and men neither were embryotoxic nor contained TH1-type cytokines, but most contained the TH2-type cytokine IL-10. Three supernatants from reproductively normal women also contained IL-4.
Conclusion: Whereas TH1-type immunity to trophoblast is associated with URA and may play a role in reproductive failure, TH2-type immunity may be a natural response to trophoblast contributing to successful pregnancy.