Forssman antigen on yolk sac derived rat tumor cells.

By means of indirect immunofluorescence (IFF) tests with rabbit antiserum to Forssman (F) glycolipid, expression of F antigen was investigated on 16 rat tumor cell lines; 14 chemical carcinogen-induced tumors, one yolk sac-derived (AT-1) tumor and another spontaneous tumor. Four lines of the carcinogen-induced tumors gave weakly positive reactions in the IIF tests and the AT-1 cells a strongly positive reaction. Flow fluorocytometric analyses on the AT-1 cell line revealed that some of the major and the vast majority of the minor population of the AT-1 express F antigen. Specificity of the F antigen demonstrated on AT-1 cells was determined by absorption experiments, in which absorption of the F antiserum with guinea pig kidney sediment, sheep red blood cells and F-liposome but not bovine red blood cells or G-liposome abolished the reaction. Results of this study together with those of our previous studies demonstrated that F antigen appears as a result of malignant transformation of F negative rat cells induced by chemical carcinogens, apparently "distorted differentiation" and the viral oncogenes.