Figure 4.

Survival of mice after tumor rechallenge and induced humoral immune response. (A) Long-term survivors were rechallenged (i.p.) with 3 × 10³ B16-F0 cells 23 weeks after Surek therapy. Six of 12 mice (50%) completely rejected the second tumor challenge in contrast to non pre-treated control mice (n = 10; log-rank test, p < 0.0001). Data of two independent experiments were summarized. (B) The binding of individual mouse plasma samples to B16 F0 cells was analyzed by FACS. Samples of long-term survivors (Surek pre-treated) or non-pretreated mice (control) were collected 14 days after tumor rechallenge with B16-F0 cells. The two analyzed sample groups are significantly different (p < 0.0001). (C) Induced tumor reactive antibodies are not directed against the target antigen GD2. Mice were i.p. treated as indicated in Figure 3 with 1 × 10⁵ B78-D14 tumor cells followed by 3 × 50 μg of Surek. Control animals were either left untreated or received only tumor cells. Three weeks after therapy, plasma samples were collected and analyzed for anti-GD2 (left panel) and for anti-B78-D14 antibodies (right panel). Only background anti-GD2 titers were detectable whereas a significant reaction with B78-D14 cells was observed in the group treated with tumor cells and Surek antibody as indicated by the asterisk (p = 0.024).