Monoclonal antibodies to human sarcoma and connective tissue differentiation antigens

The use of monoclonal antibodies to distinguish human sarcoma from carcinoma cells has been explored. Spleen cells from a BALB/c mouse immunized with a human malignant fibrohistiocytoma were fused with cells of the mouse P3U1 plasmacytoma cell line. Antibodies were then screened for reactivity against human sarcoma and carcinoma cells growing in culture. This work has yielded 2 immunoglobulin G monoclonal antibodies VIE4 and VIF3 which, respectively, reacted with 85% (17 of 20) and 90% (18 of 20) of sarcoma lines tested but with none of eight carcinoma cell line preparations. Reactivity against normal fibroblasts was also demonstrated. By immunofluorescence, the antigens detected by the two antibodies appear to have distinctive intracellular distributions. Immunoprecipitation with VIF3 has shown that it is detecting a protein with a molecular weight of 70,000. When tested against pathological frozen tissue sections, VIF3 reacted with four of 11 and VIE4 with three of 11 human sarcomas but with none of ten carcinomas tested. VIF3 occasionally bound to normal adult connective tissues, whereas no such reactivity was seen with VIE4. These antibodies appear to be directed to fibroblastic markers associated with sarcomas and connective tissue differentiation antigens.