Independence of Moloney virus-induced cell-surface antigen and membrane-associated virion antigens in immunoselected lymphoma sublines

Abstract

THE nature of virus-determined cell-surface antigens (CSAs), recognised by the syngeneic host on neoplastic cells induced by RNA viruses has not been properly defined in spite of much recent speculation about the possible role of cell membrane associated virion proteins¹. Lymphoma cells induced by the Moloney leukaemia virus (MLV) are said to carry MCSAs. It is a matter of some debate whether MCSA is identical with the tumour-associated transplantation antigen (TATA) detected in vivo by the rejection of small tumour grafts in syngeneic preimmunised animals. Views are divided on the origin and control of CSA and/or TATA: some authors regard them as virally induced, but distinct from virion antigens (see for example refs 2–5) whereas others believe that they are virion components, inserted into the cell membrane^6,7. Antisera against purified virion components (designated according to the recently adopted nomenclature⁸) have been used to demonstrate that p30 and gp69/71 are present on the surface of mammalian type C RNA virus-infected cells^9–11. We have confirmed this in the present paper using an MLV-induced mouse lymphoma (YAC) and shown, in addition, that antigen(s) identical with or related to p15 and p12 are also expressed on the outer cell surface. Since these specificities were all detected with antisera produced in foreign species, the question as to which, if any of them, is responsible for MCSA, the antigen recognised by the syngeneic mouse—as mentioned above—remains open. We have approached this question by exposing the YAC lymphoma repeatedly to the immunoselective pressure of anti-MCSA sera and passage through preimmunised syngeneic hosts, until all detectable MCSA has disappeared. The immunoresistant sublines were compared with the original YAC line with regard to the expression of the various virion antigens. The results support that MCSA differs from the known virion antigens, partly or completely.