Fig. 5.

Memory CD4 T cells reactivated with antigen alone can provide help to B cells. B6 mice immunized with 3K with/without LPS i.v. as indicated were injected with 3K-OVA and alum i.p. 40 d after Imm2. After an additional 6 d, the amount of anti–OVA-specific IgG in the serum was examined. The data are combined from two independent experiments with four mice per group. Significant differences between the groups and primary responding mice are indicated by *P < 0.05, ***P < 0.001; ns, not significant, error bars are SEM.