EMBRYO-ASSOCIATED IMMUNOSUPPRESSOR FACTOR IS PRODUCED AT THE MATERNAL-FETAL INTERFACE IN HUMAN-PREGNANCY

PROBLEM: To study whether embryo associated immunosuppressor factor (E ASE) is synthesized at the maternal-fetal interface. METHOD: Anti-EASE monoclonal antibody H5D12 was used to identify EASE Paraffin-embedded sections were prepared from placental and fetal tissues and immunohis tochemistry was done by the avidin-biotin-peroxidase technique. EASF w as affinity purified using HSD12-Sepharose 4B from culture media of pl acental villi and analyzed for immunosuppressive activity (by Concanav alin A-induced lymphocyte proliferation assay) and molecular weight id entity (by metabolic labeling studies with S-35-methionine followed by immunoprecipitation and SDS-PAGE). RESULTS: Immunohistochemical studi es demonstrates intense immunostaining of villous syncytiotrophoblast and cytotrophoblast cells of first trimester placental tissues. Hoffba uer cells and decidual cells stained positive. The same cells in secon d and third trimester placental tissues stained weakly. However, the e ndothelium and smooth muscle cells of fetal blood vessels, fetal ovari an stroma and primordial follicles, kidney epithelium, cerebral neuron s, and gliaI cells all stained negative. The affinity-purified EASE fr om the conditioned media of placental villi (less than 12 wk gestation al age) was identified as a 37-kDa molecule with immunosuppressive act ivity. Metabolic labeling studies revealed that placental villi from e arly gestational age secretes a major factor of 37-kDa and minor facto rs of 41-kDa and 47-kDa molecular weight. CONCLUSIONS: Monoclonal anti body H5D12 identifies a factor that is produced by the pre-implantatio n embryo and also synthesized by decidua and trophoblast cells.