Effect of Ribi coadministration on tolerance induction and response to sialylated and unsialylated antigens. (A) Mice received the indicated conjugates in the presence or absence of Ribi; serum IgM and IgG3 anti-NP levels were measured on days 7 and 14. (B) Mice were treated with the tolerogenic compound NP–PA–bNeuGc with or without Ribi on day 0, and were rechallenged on day 18 with NP–PA. Shown are serum anti-NP titers monitored on day 25. Results are representative of three experiments. For all experimental groups, eight mice were analyzed. Shown are means + SD. All statistical tests given used the two-tailed Student’s t test. *, P < 0.05; ***, P < 0.005. n.s., not significant.