The effect of NK cells and Fc-dependent mechanisms on the therapeutic activity of B1 mAb in SCID mice. (A) Groups of 4 to 5 SCID mice were injected with 2.5 × 106 Daudi cells intravenously on day 0, and then treated with 100 μg B1, 1F5, or PBS (control) intravenously on day 7. In the NK-depleted groups (solid symbols), the animals were injected with 25 μg anti-ASGM1 (ASGM1) intraperitoneally on days 5 and 9 after tumor inoculation. (B) Groups of 4 to 5 SCID mice were injected with 2.5 × 106 Daudi cells intravenously on day 0 and then treated with 100 μg B1 or 1F5 IgG (open symbols) or F(ab′)2 fragments (solid symbols) or PBS intravenously on day 7. Additional 100-μg injections of F(ab′)2 were given intraperitoneally on day 7, intravenously and intraperitoneally on day 8, and intraperitoneally on day 9, to a total of 500 μg. (C) Samples of the IgG and F(ab′)2 fragments of the IF5 and B1 mAb used in panel B were assessed by SDS-PAGE analysis under reducing conditions. The Fd and light (L) chain fragments of the reduced B1 F(ab′)2 comigrate. Note, the absence of contaminating heavy (H) chains in both F(ab′)2 preparations.
