Tosis in Vivo. SCID/beige mice wereAldrich (St. Louis, MO); the antibody to HLA-A,B,C #G46?.6 was from BD Biosciences (San Diego, CA). Fragments of W6/32, including F(ab )2 and Fab, were prepared by using a kit according to the manufacturer's instructions (ImmunoPure Fab Preparation Kit; Pierce, Rockford, IL). The antibody to cross-link the F(ab) fragment was goat anti-mouse IgG that was cleaved a