Immunoregulatory activity of decidua in spontaneous early pregnancy loss.

The present study aimed to address whether the immunoregulatory properties of the molecules secreted within decidua were altered in women suffering spontaneous miscarriage, compared with apparently normal fertile women. Unfractionated decidual cells from 22 women undergoing therapeutic pregnancy terminations and 25 women experiencing a sporadic spontaneous early pregnancy loss were isolated, cultured for 24 h and 72 h, and supernatants were collected. The effect of decidual supernatants on phytohaemagglutinin (PHA)-induced peripheral blood lymphocyte proliferation was investigated. Immunosuppressive activity was detected in 24 h cell culture supernatants from 91% of therapeutic abortion cases compared with only 64% of spontaneous abortion samples; 72 h supernatants from all of therapeutic abortion samples and 90% of spontaneous abortion cases suppressed lymphoproliferation. The remaining spontaneous abortion samples (36% of 24 h supernatants; 10% of 72 h supernatants) enhanced or had no effect on lymphocyte proliferation. Enhancement of lymphocyte proliferation was not observed in therapeutic abortion samples, and the association between stimulation of cell proliferation and spontaneous abortion was significant for 24 h decidual cell supernatants at 50% concentration (P = 0.02). These findings suggest that in a subgroup of women experiencing spontaneous early pregnancy loss, soluble factors within decidua display altered immune responses that may be implicated in the complex process of fetal rejection.