FIG. 2.

Neutralization of in vivo toxicity in mice. (A) Mice were treated with 100 to 250 μg either of an irrelevant HuMAb or of 1B11, CDA1, or 3H2 24 h prior to intraperitoneal administration of 100 ng of toxin A. Animals were observed for up to 72 h, and the percentages of surviving animals were plotted. The number of animals tested in each group is shown above the respective column in the bar graph, with P values indicated (the Fisher exact test). NS, not significant. (B) Mice were injected i.p. with 500 μg to 2 mg of 1B11, CDA1, or 3H2 24 h prior to ileal loop surgery. As an untreated positive control, mice were injected i.p. with PBS rather than antibody (no antibody). As a negative control for fluid accumulation due to surgery, PBS was injected into the ligated loop in place of toxin A (no toxin). The number of animals in each group is shown above the respective column in the bar graph. Toxin A (0.45 μg) was injected into ligated ileal loops of treated animals, and loops were excised 4 hours later. Weight-to-length ratios were calculated and plotted.