Fig. 6.
Memory CD4 T cells reactivated twice with antigen alone do not survive and therefore cannot provide accelerated help for antibody production. B6 mice were immunized with/without 3K peptide and LPS i.v. as indicated with immunizations given 40 d apart. Six days following immunization with 3K-OVA and alum i.p., the numbers of splenic CD4 T cells that were IAb/3K tetramer+ CD44hi were examined (A) and the levels of anti-OVA IgG in the serum determined (B). In A, each point represents a mouse and the lines show the mean of the group, * indicates groups with means significantly greater than background, determined by staining naive splenoctyes with IAb/3K tetramer, the mean of which is indicated by the x axis. In B, error bars are SEM. In both, the data are combined from two experiments with four mice per group and in B, significant differences are indicated by *P < 0.05, **P < 0.01, and ***P < 0.001.