Fig. 2.

Innate-like B1 cells are involved in the rapid generation of F1-mediated anti-plague immunity. a Anti-F1 IgM titers in the sera of wild-type CBA-Ca/J mice (blue circles, n = 12) and Xid mice (red squares, n = 12) 3 days post vaccination with F1 (polymeric form, 80 μg/mouse). b Survival curves of CBA-Ca/J (blue line, n = 12) and Xid mice (red line, n = 12) vaccinated with F1 3 days prior to a lethal challenge with Y. pestis Kim53. Control mice were vaccinated with alum (n = 9, dashed black line). c Anti-F1 IgM and IgG titers in the sera of CBA-Ca/J mice (blue circles, n = 8) and Xid mice (red squares, n = 5) 14 days post vaccination with F1. d Survival curves of CBA-Ca/J mice (blue line, n = 8) and Xid mice (red line, n = 5) vaccinated with F1 14 days prior to the challenge indicated above. Black dashed line indicates the survival of alum-vaccinated animals (n = 8). Short horizontal lines mark the GMT ( ± 95% CI). Horizontal dashed line indicates the limit of detection. (***P < 0.001, ns = nonsignificant)