Close Association of Virus‐Specific Cell Surface (S) and H‐2 Antigens in Ad12‐Infected and ‐Transformed Mouse Cells

Abstract

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

Effector Cells Working for Rejection of Ad12 Tumors in Mice

“…T-Iymphocytes bearing Lyt-2.2 antigen are considered to be the prime effectors in ISC. Although the precise function of these Lyt-2.2+ lymphocytes was not analyzed in this study, the most plausible function is direct killing of the tumor cells by acting as cytotoxic T-lymphocytes (CTL) (II,12). In fact, the same schedule for immunization of mice with Ad 12 as described herein can induce CTL which specifically lyse Adl2-transformed cells in vitro (11).…”

“…However, all these findings are still circumstantial in regard to our understanding of the precise mechanism for generation of cellular immunity to Adl2 tumors. Thus, even for the effector cells, there is no definitive proof of the cell species that attacks the tumor cells in vivo, though in vitro investigations point to cytotoxic T-Iymphocytes as possible candidates for the effectors (7,II,12,20).…”

“…Immunoadjuvants known to stimulate cellular immunity augment the rejection reaction of animals against Adl2 tumors (5,16,19). Lymphocytes from animals made immune to Adl2 tumors damage the tumor cells in vitro (7,II,12,20). Animals immunized with Adl2-tumor antigens give rise to delayed hypersensitivity as revealed by macrophage-migration inhibition (IS,18).…”