Suppression of lymphocyte proliferation in vitro by macromolecules in the vesicle fluid and tissue extracts of hydatidiform mole.

This study examines the effects of vesicle fluid and tissue extracts from hydatidiform mole trophoblast on lymphocyte proliferation in vitro. Samples were obtained by direct aspiration of vesicles (hydatidiform mole vesicle fluid (HMF] or homogenization of molar tissues (hydatidiform mole extract (HME] following therapeutic uterine evacuation of hydatidiform mole. Dialyzed and lyophylized HMF pooled from two patients exhibited a 30% suppression (P less than 0.05) of mitogen-induced lymphocyte proliferation at a concentration of 12.5 micrograms protein/ml. Similarly, lymphocyte transformation was significantly suppressed (P less than 0.05) by HME at concentrations of 500 and 250 micrograms/ml. Molecular weight chromatography of HME resolved 4 protein fractions. Fraction 3 (35--50 kDa) and fraction 4 (less than 35 kDa) significantly suppressed mitogen-induced lymphocyte transformation while fractions 1 and 2 demonstrated no immunosuppression. Heat treatment (56 degrees C, 30 min) abolished the immunosuppressive activity of HME as well as fractions 3 and 4. These results suggest that hydatidiform mole trophoblast contains heat-labile macromolecules which suppress mitogen-mediated lymphocyte transformation. Such trophoblast-derived factors may interfere with maternal rejection of the allograft.