Recent studies have implicated T helper type 1 CYTs (TH1) including IFNg, TNFa & IL2 in imparting deleterious effect on the conceptus by promoting cell mediated immune response. The purpose of this study is to test the hypothesis that the placenta(PL) in early preg.(EP) protects itself by producing counteracting TH2 type CYTs including IL4, IL6 & IL 10 which down regulate harmful THl CYTs. We used enzyme immunoassay to study CYT production from PL culture, stimulated maternal peripheral blood mononuclear cells PBMCs, from both EP (8-12 wks) and late preg.(LP) before onset of labor(38-40 wks) and from stimulated PMBCs of healthy, non-preg women as a control group. Results are expressed as concentration (pg/ml) of CYTs from the supernatant culture media and presented as Mean±SE. (· EP vs non-preg * LP vs non-preg) Table

Table 1

Using mouse monoclonal antibody specific for IL10, immunohistochemical analysis of PL specimens demonstrated ↑ production of IL10 from EP compared to LP, moreover, PL IL10 was biologically active as assayed on activated normal human B cells. Our results suggest that PL IL10 is significantly ↑ in EP compared to LP in contrast to the harmful CYTs IFNγ and IL1. On the other hand, stimulated maternal PBMCs produc more IFNγ and IL1 in EP. We conclude that during human preg. the PL appears to constitute a unique local immune environment which may be different from systemic immune system, by producing immunoregulatory TH2 type CYT, namely IL10 which down regulates the production of the PL harmful CYTs. (Supported by NIH grant CA 55910(S.S.))