EXPRESSION OF B7-1 BY HIGHLY METASTATIC MOUSE T-LYMPHOMAS INDUCES OPTIMAL NATURAL-KILLER CELL-MEDIATED CYTOTOXICITY

The interaction between B7-1 and CD28 provides costimulatory signals n ot only for T cells but also for natural killer (NK) cells, Highly met astatic mouse T lymphoma cells (BW-Li) can escape from MK cell-mediate d killing by expressing H-2D(k) molecules that negatively regulate NK lytic activity, We have analyzed whether B7-1:CD28 overrules the MHC c lass I-mediated inactivation of NK cells by transfecting BW-Li with th e gene coding for B7-1, Expression of B7-1 rendered BW-Li cells sensit ive toward NK cells, The experimental metastatic capacity of the B7-1 transfectants was drastically reduced in both syngeneic AKR and SCID m ice but could be restored in SCID bg mice, These results provide direc t evidence that B7-1 expression leads to NK-mediated elimination of me tastasizing, NK-resistant tumor cells.