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J. Exp. Med.,
Volume 189, Number 6, March 15, 1999 919-930
By


From the * Center for Neurological Diseases, Brigham and Women's Hospital, and Department of
Neurology, Harvard Medical School, Boston, Massachusetts 02115; and the For T cells to become functionally activated they require at least two signals. The B7 costimulatory molecules B7-1 and B7-2 provide the "second signal" pivotal for T cell activation. In this report, we studied the relative roles of B7-1 and B7-2 molecules in the induction of antitumor immunity to the T cell thymoma, EL4. We generated EL4 tumor cells that expressed
B7-1, B7-2, and B7-1+B7-2 by transfecting murine cDNAs. Our results demonstrate that
EL4-B7-1 cells are completely rejected in syngeneic mice. Unlike EL4-B7-1 cells, we find that
EL4-B7-2 cells are not rejected but progressively grow in the mice. A B7-1- and B7-2-EL4
double transfectant was generated by introducing B7-2 cDNA into the EL4-B7-1 tumor line
that regressed in vivo. The EL4-B7-1+B7-2 double transfectant was not rejected when implanted into syngeneic mice but progressively grew to produce tumors. The double transfectant EL4 cells could costimulate T cell proliferation that could be blocked by anti-B7-1 antibodies, anti-B7-2 antibodies, or hCTLA4 immunoglobulin, showing that the B7-1 and B7-2
molecules expressed on the EL4 cells were functional. In vivo, treatment of mice implanted
with double-transfected EL4 cells with anti-B7-2 monoclonal antibody resulted in tumor rejection. Furthermore, the EL4-B7-2 and EL4-B7-1+B7-2 cells, but not the wild-type EL4
cells, were rejected in interleukin 4 (IL-4) knockout mice. Our data suggests that B7-2 expressed on some T cell tumors inhibits development of antitumor immunity, and IL-4 appears to
play a critical role in abrogation of the antitumor immune response.
Department of Adult
Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115
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