Alloantigen expression of a rat Moloney sarcoma.

Cells of a brown Norway (BN) rat Moloney sarcoma (MST) failed to express certain BN alloantigen specificities and bound only about 30-50% the amount of labeled alloantibody bound by normal BN spleen cells. MST cells lacked antigen specificities shared by BN and WF rats, but expressed some of the antigen shared by BN and AUG rats. Further loss of alloantigens that occurred with prolonged in vitro culture was associated with reduced virulence of MST cells for syngeneic hosts and with increased expression of tumor-associated antigens. The LEW rats, which are resistant to MST cells, might have rejected the tumor on the basis of factors other than Ag-B antigens.