Cross-reactions between cell surface membrane antigens of human trophoblast and cancer cells

This report describes cross-reactivity between cell surface membrane antigens of human trophoblast and certain transformed cells. Heterologous antisera were raised to chaotrope extracted, intact and solubilized trophoblast microvillous pellets. Antisera to microvilli, after absorption with human erythrocytes and serum proteins, reacted with trophoblast, endothelium and stromal cells of chorionic villi as well as with all other human tissues tested. This group of antigens was designated TA2. Further absorptions of the TA2 antisera with normal human tissues such as liver, kidney or peripheral blood leucocytes, removed all immunofluorescent reactivity except for the apical aspect of syncytiotrophoblast and membranes of the human transformed cell lines HEp-2, AV3 and Chang liver. This group of antigens was designated TA1. Absorption with trophoblast membrane pellets removed all TA1 and TA2 antibody activity. Rabbit antisera raised to the first peak of DOC solubilized syncytiotrophoblast microvilli were shown to have identical patterns of immunofluorescent reactivity to that described for TA1. Cytotoxicity assays with the antisera confirmed the immunofluorescent findings of species specificity and the inability to absorb out reactivity to the cell lines expressing trophoblast cross-reactive antigens with normal tissues. Exhaustive absorptions with AV3 and HEp-2 cell lines removed all immunofluorescent and cytotoxic activities. We propose that the trophoblast cross-reactive antigens present on certain transformed cell lines represent an adaptive response of tumour cells to natural selection pressures as a biological response to resist immunological recognition and rejection by the host.