A nonspecific human IgG1 antibody (Hu-IgG1) had little effect on the mean-time-to-death (MTD) and number of surviving mice that received the human anti-F1 mAb.

<p>The nonspecific human IgG1mAb, and the human and mouse anti-F1 and anti-V mAbs were given i.p. to mice 24 hrs before parenteral challenge with <i>Y. pestis</i> CO92, and the number of surviving mice for each treatment group was monitored for 21 days after challenge. Mouse or human mAbs and their amounts were given to the following groups of mice: nonspecific human IgG1 (Hu-IgG1, 1,500 µg); F1m (F1m, 500 µg); F1m (500 µg) + Hu-IgG1(1,000 µg); m252, 500 µg; m252 (500 µg) + Hu-IgG1 (1,000 µg).