Surface antigen expression in malignant sublines derived from hybrid cells of low malignancy

Ehrlich ascites tumour cells were fused with three L cell derivatives A9, B82 and A9RI, and the surface antigens of the resultant hybrid cells examined. The expression of three surface antigens contributed to the hybrid cells by the L cell derivatives, the H-2^k isoantigen, the virus-induced Moloney-type antigen and the L antigen, was examined by the membrane immunofluorescence and mixed hemadsorption tests. The hybrid cells showed complete or partial suppression of the surface antigens. The hybrid cell lines had a low level of malignancy, but threw off occasional segregant sublines of high malignancy. In these malignant sublines, the three surface antigens reappeared independently of each other. The reappearance of these antigens was accompanied by substancial chromosome losses. This appeared to indicate that the Ehrlich cell possesses mechanisms for the suppression of surface antigens, and that the reappearance of these antigens in segregant tumours results from the loss of the chromosomes determining antigenic suppression.