Adenovirus type 12 (Ad12)-transformed mouse cells were examined for their susceptibility to cell-mediated immunity in vitro, with respect to the activity of the virus-specific surface (S) antigen in the cells. A transformed cell line, C57ATl, was established from embryonic cells of C57BL/6 mice by Ad12 infection. In fluorescent antibody tests, the transformed cells were positive for the S antigen when the cells were maintained as cultures, whereas when the cells were grown as tumors in animals they became negative for the antigen (referred to as S(+) and S(-) cells, respectively). These S(+) and S(-) cells were subjected to the 51Cr-release test for cell lysis by immune spleen cells (ISC) raised in syngeneic mice by Ad12 infection. When the S (+) cells at various passage levels were exposed to ISC, all of them were lysed extensively and to a similar extent irrespective of their passage history. In contrast, the S(-) cells were consistently refractory to the action of ISC. In addition, the cytotoxic action of ISC was markedly impeded by pretreating the S(+) cells with antiserum to the S antigen, or the ISC with anti-Thy-1,2 serum plus complement. Taken these findings together, the S(+) cells were assumed to be injured by ISC through direct interaction of the S antigen with T-lymphocytes.In the tumors induced by adenovirus type 12 (Ad12), a virus-specific antigen has been located in their cell surfaces by the in vitro methods of cytotoxicity (2, 5, 17, 27, 28) and of fluorescent antibody (FA) technique (15,21,31), and the in vivo method of immunorejection revealed a virus-specific TSTA (tumor-specific transplantation antigen) (3-7, 11, 12, 18, 22-24, 28-30). However the relationship between the two antigens is not yet fully established. Of these antigens, the one shown by the FA technique and called surface (S) antigen was readily detectable in Ad 12-transformed cells cultured in vitro (15, 21), but not in tumor cells grown in animals unless the cells were treated with a low concentration of trypsin (31). In a previous paper, we described alternate changes of the S antigen on Ad12-transformed cells cultured in vitro and grown in animals (21). In the FA test, while all of the hamster and mouse cells transformed with Ad12 showed specific and distinct membrane fluorescence, the tumor cells produced by grafting the transformed cells, did not show any fluorescence (referred to as S(+) and S(-) cells, respectively). In the same paper, it was also shown that the S(+) cells were less tumorigenic and more immuno-1085

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A virus-specific cell surface (S) antigen in adenovirus type 12 (Ad12)-transformed mouse cells has been assumed to be a direct target for cytotoxic thymusderived lymphocytes (CTL). In this study, the spatial proximity between the S and H-2 antigens was determined by three different methods, the proximity and co-capping tests, and the test for blocking of CTL-mediated lysis by anti-H-2 serum. In the proximity test with Ad12-infected thymic and splenic lymphocytes, and an Ad12-transformed line of C3H/He (H_2 k ) mouse cells, anti-Hvz" and anti-S sera reciprocally inhibited fluorescent-antibody staining of the opposite antigens. By contrast, anti-Thy-1, 2 serum as well as anti-Ia and anti-Ig sera failed to show any appreciable effect in this test, when paired with anti-S serum. In addition, the Sand H-2 antigens co-capped in the infected thymic lymphocytes, and CTL-mediated lysis of the transformed cells was abrogated equally by treatment of cells with anti-S and anti-H-2 sera. These results clearly demonstrate that there is a close proximity between the Sand H-2 antigens on the surface of Ad12-infected and -transformed mouse cells.In adenovirus type 12 (Ad12)-infected and -transformed cells, a virus-specific cell surface (S) antigen was detected by the fluorescent-antibody technique (18,39). In the transformed cells, the S antigen was readily detected when the cells were cultured in vitro, but was undetectable when the cells were grown as tumors in animals (29) (referred to as S( +) and S( -) cells, respectively). In animals, the S( +) cells were less tumorigenic and more immunosensitive than the S( -) cells (29). In in vitro tests, the S( +) cells were more efficiently lysed by cytotoxic thymusderived lymphocytes (CTL) than were the S( -) cells, and the effect of cytotoxicity was markedly inhibited by pretreatment of the S( +) cells with antiserum to the S antigen (17,26). Thus, the S antigen of Ad 12-transformed cells was designated as a primary target for the tumor rejection reaction in animals, especially for that exerted by CTL.On the other hand, virus-infected murine cells are recognized by CTL for both viral and murine major histocompatibility (H-2) determinants to yield cyto-1 This work was done in partial fulfillment of the requirements for Y. Maeta's degree of Doctor

Immune spleen cells (ISC) capable of inhibiting the growth of adenovirus type 12 (AdI2) tumors were raised in C57BL/6 mice by immunization with Ad12, fractionated according to their affinity for plastic and nylon-wool substrates or treated with various antisera plus complement, and subjected to the tumorneutralization test (Winn) to define the effector cells for the cell species. Full antitumor activity of ISC was recovered in the cell fractions nonadherent to the two substrates; the antitumor activity of ISC was abrogated entirely by antiThy-I,2 serum and almost entirely by anti-Lyt-2.2 ascites fluid plus complement. These results clearly indicate that T-Iymphocytes, particularly those bearing Lyt-2.2 antigen, are the principal effectors in ISC against Adl2 tumors in animals.