FIG. 1.

Evaluation of whether immunological tolerance to flagellin occurs in BALB/c mice immunized by the oral route with S. enterica serovar Dublin ICB5. Mouse groups 1 and 3 were immunized with three doses of 10¹⁰ CFU of the ICB5 strain on days 0, 21, and 35. Mouse group 2 was maintained as a control and was not immunized by the oral route. One week after the last immunizing dose, mice in groups 2 and 3 were injected i.p. with two doses of the ICB5 strain (SD) (10⁷ CFU) (A) or two doses of 10 μg of purified flagellin (FLA) (B) separated by a 2-week interval (group 3). Antiflagellin (IgG) antibody responses in sera were measured 1 week after the last i.p. immunization. Five animals were used for each immunization group. Values are expressed as means of end point titers ± SEM for serum pools prepared from each mouse group.