title: T cell costimulation by B7/BB1 induces CD8 T cell-dependent tumor rejection: an important role of B7/BB1 in the induction, recruitment, and effector function of antitumor T cells.
abstract: A successful antitumor T cell immune response involves induction, recruitment, and effector function of T cells. While B7/BB1 is known as a major costimulatory molecule in the induction of T cell responses, its role in T cell recruitment and effector function is still unclear. In this study, we show that introducing a major costimulatory molecule B7/BB1 into a major histocompatibility complex class II-negative tumor cell line, J558, results in a drastic reduction of its tumorigenicity. The tumor rejection depends on CD8 T cells but not CD4 T cells. However, unlike the previous reports on melanoma cell lines, B7/BB1-transfected J558 cells fail to induce cross-protection against parental J558 cells. The B7/BB1-transfected (J558-B7), but not untransfected J558 cells (J558-Neo) induce a CD8 T cell-dominant inflammatory response, and the T cells isolated from the tumor infiltrating lymphocytes (TIL) are polyclonal in terms of their T cell receptor V beta usage. Most surprisingly, the freshly prepared TIL have a potent, CD8 T cell-mediated cytotoxicity on tumor cells without any in vitro stimulation. The cytotoxic T lymphocyte (CTL) activity can be blocked by anti-CD8 monoclonal antibody (mAb). Interestingly, the CTL lyse J558-B7 about 10- to 80-fold more efficiently than untransfected J558-Neo cells. This preferential lysis cannot be attributed to recognition of B7/BB1-derived antigen by the T cells. This finding, together with the lack of the cross-protection between the J558-B7 and J558-Neo, suggests that B7/BB1 can also function at the effector phase of CTL responses. This notion is confirmed by our findings that the lysis of J558-B7 can be blocked by anti-B7 mAbs. Taken together, our results indicate that not only can the B7/BB1 molecule function as a costimulatory molecule at the initiation of immune response, it can also play a major role in T cell recruitment and effector function. This conclusion has significant implications for immunotherapy of tumors.
authors.affiliation: Michael Heidelberger Division of Immunology, Department of Pathology, New York University Medical Center, New York 10016.
authors.forename: L
authors.initials: L
authors.lastname: Ramarathinam
authors.forename: M
authors.initials: M
authors.lastname: Castle
authors.forename: Y
authors.initials: Y
authors.lastname: Wu
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000818:Animals; D018122:B7-1 Antigen / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D016827:CD8 Antigens; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009374:Neoplasms, Experimental / Q000276:immunology*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014162:Transfection; D014407:Tumor Cells, Cultured; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7 / Q000276:immunology*
chemical_list: D018122:B7-1 Antigen; D016827:CD8 Antigens; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7