Xeno-immunization does not produce long-term antitumor protection, which requires intact CAT-13 mAb in vivo. (A) Mice were intravenously injected on day 0 with either 5 × 105 DOX-treated EL4-huCD20 cells (×, n = 8) or 5 × 105 EL4-huCD20 cells (n = 14). The latter mice were divided into 2 groups. The first group was left untreated (□, n = 6) and the second received CAT-13 mAb therapy (■, n = 8). *P < .001. (B) Surviving CAT-13–treated mice (■, n = 6) and mice previously injected with DOX-treated EL4-huCD20 cells (×, n = 8) were challenged intravenously with 5 × 105 EL4-huCD20 cells. Control naive mice were injected intravenously with 5 × 105 EL4-huCD20 cells (□, n = 6). **P = .03. (C) Mice were intravenously injected on day 0 with 5 × 105 EL4-huCD20 cells (n = 18) and divided into 3 groups. The first group was left untreated (□, n = 6). The second group received the CAT-13 mAb therapy (■, n = 6). The third group received CAT-13 F(ab′)2 therapy (5 × 150 μg intraperitoneally on days 1, 4, 7, 10, and 13; ▴, n = 6). ***P < .001. Black arrows indicate CAT-13 mAb and CAT-13 F(ab′)2 fragment injections. Statistical comparisons were performed with the log-rank test.
