Interaction of trophoblast membranes with lymphocytes and other cells.

Certain proteins present in trophoblast membranes may be instrumental in assuring the successful cohabitation of allogeneic tissues in the materno-fetal relationship of normal human pregnancy, inasmuch as preparations of trophoblast microvilli can specifically impede the progress of immune recognition reactions, as measured by the mixed lymphocyte culture (MLC) reaction. Microvilli prepared from fresh placentae were extracted with 3 mol/1 KCl and solubilized overnight in 1 per cent sodium deoxycholic acid (DOC). Following ultracentrifugation, the DOC supernatant chromatographed on Bio-Gel P-200 yielded two major protein peaks. The first peak (P1) was observed to eliminate MLC reactivity, impede the spontaneous turnover of T-cell-enriched populations and interfere with the proliferation of the Daudi lymphoblastoid B cell line. Sepharose CL-6B chromatography of KCl-extracted, DOC-solubilized microvilli yielded a broad peak (m.w. 5 X 10(4) to 5 X 10(5)); 5 micrograms of this specifically abrogated all MLC reactivity while leaving lymphocyte responses to lectins unaffected. The composition of the MLC-inhibitory peak was analysed by using SDS polyacrylamide gel electrophoresis under reducing conditions; it revealed 15 protein bands, six of which also stained for glycoproteins.