solid phase radioimmunoassay with l?51-protein ~ to study the humoral immune response of parous females to antigens associated with membrane extracts of the cell lines F9 and PCC4. These cell lines were derived from the teratocarcinoma OTT6050 and express antigens found on early embryos and sperm of a l l mammals studied. Compared to sera from v i r g i n female mice, sera pools from C57~I,/6 female mice r e t i r e d from breeding to C57~IL/6 males or A/J males were 3-15 times more reactive with both the F9 and PCC4 antigens and were not reactive with 129 spleen cell antigens. The r e a c t i v i t y to PCC4 was lower than that to Fg, This r e a c t i v i t y was not due to the older age of the parous females, since sera from v i r q i n female mice over 1 year old were not reactive with either antigen. Sera from 3 selected multiparous humans extensively absorbed with mouse spleen c e l l s w e r e a l s o reactiue with both onco-fetal antigens. Ile conclude that parity and not age induces an immune response to onco-fetal antigens. Supported by The Milton Fund and Grant AI-~15,~77.
MONOCLONAL ANTIBODIES TO HUMAN TROPHOBLASTANTIGENS Marc L i p i n s k i , David R. Parks and Leonard &. Herzenber 9, Department of Genetics, Stanford University School of Medicine, Stanford, Ca 94305, U.S.A. Fetal cells of unknown histological type circulate in pregnant women,s blood. This was demonstrated by staining cells from pregnant women's blood samples with quinacrine to detect cells expressing a Y body and by correlating this finding with the following b i r t h of a male. I t is possible to enrich for fetal cells present in maternal blood by sorting with a Fluorescence-Activated Cell-Sorter (FACS) cells that have been tagged with fluorescent antibodies s p e c i f i c a l l y reacting with the fetal c e l l s . We have raised a series of monoclonal antibodies to trophoblast antigens expressed on a human choriocarcinoma c e l l - l i n e , BeWo. Two of these antibodies appear to s p e c i f i c a l l y react with tro~ phoblast c e l l s . We w i l l use these to investigate the presence of fetal placenta cells in maternal blood. These antibodies to antigens s p e c i f i c a l l y expressed on normal and tumoral trophoblast cells might also prove useful as diagnostic and therapeutic agents in patients with choriocarcinoma. Supported by NIH 9rants HD 13025 and GM 17367