FIG. 2.

Serum IgG, IgA, and IgM antibody responses of C57BL/6 mice prior to immunization (day 0) and 7, 12, 23, 35, and 90 days after oral immunization with 10⁸ organisms of the indicated Yersinia mutant strains, as determined by using a Yersinia outer protein-specific ELISA. Columns represent means and standard deviations of results (log₁₀ titer) obtained from eight mice. ∗, value differs from that of a control serum obtained prior to oral immunization (P < 0.05).