FIGURE 5.

LT-K63 increased the frequency of Pnc1-TT–specific AbSCs. PPS-1– and TT-specific IgG⁺ AbSCs measured by ELISPOT, shown as number of spots (mean ± SD) per 10⁶ cells (A, B), and PPS-1– and TT-specific IgG levels (mean EU/ml ± SD) in serum measured by ELISA (C, D). Results are shown for neonatal (filled bars) and adult (open bars) mice immunized with 0.5 μg Pnc1-TT with or without 5 μg LT-K63, LT-K63, or saline. Spleens were removed 14 or 10 d after priming, when GCs and AbSCs peak in neonatal and adult mice, respectively (14), and single-cell suspension was prepared from half of the spleen. Statistical difference between test groups and controls (LT-K63– and saline-immunized mice) are shown; *p < 0.05, **p ≤ 0.001. Results in (A)–(D) are from three experiments for neonatal mice (n = 24 per group, except for LT-K63 injected mice n = 16) and two experiments for adult mice (n = 16 per group, except for LT-K63–injected mice n = 8), with eight mice per group in each experiment.