Fig. 3: CTA1-DD adjuvant accelerates FDC expansion and maturation also in neonatal draining lymph nodes.

a Tissue sections from spleen, iLN, or PP from unimmunized naive neonatal (7-day-old) or infant (17-day-old) CD21^mT/mG mice. Tissues were stained for B-cell follicles (B220⁺, blue) and FDC (CD35⁺, white). The size bars indicate 100 µm. b CD21^mT/mG mice were immunized s.c. with 10 μg CTA1-DD on post-natal day 3. FDC (GFP⁺ CD21⁺ CD19^- CD45^- CD31^- tdTomato^-) were sorted 4 days after immunization (post-natal day 7) and Cxcl13 gene expression in FDC from iLN was assessed in CTA1-DD immunized neonate mice and compared to that observed in naive 17-day-old mice. Results are given as the mean fold-change ± SD (2^ddCt) and statistical significance was determined by student’s t-test, *p < 0.05. c Maturation of neonatal FDCs was assessed in tissue sections from iLN from 7-day-old CD21^mT/mG mice with or without a s.c. immunization with 10 μg CTA1-DD adjuvant given 4 days before. Representative microtome sections; red: tdTomato, green: CD21-GFP, white: CD35, blue: CD16/32. The size bars indicate 50 µm. d, e, f CD21^mT/mG mice were immunized s.c. with 5 µg NP-OVA with or without 10 μg CTA1-DD on post-natal day 6. d Tissue sections of iLN from CTA1-DD adjuvant immunized neonatal (post natal on day 6) or adult CD21^mT/mG mice and analyzed 12 days later for GC reactions by labeling for B220 (blue) and GL-7 (red). The size bars indicate 100 µm. e The frequency of B-cell follicles containing a GC was determined as the mean ± SD from ten sequential sections of iLN from three mice in each group. All images were taken with an inverted confocal microscope (LSM700) with x20 magnification. f Serum levels of IgG anti-NP log₁₀ titers were determined by ELISA after 12 and 35 days following a priming and 5 days following a booster immunization on day 30, respectively. A statistical analysis was performed using two-way ANOVA followed by Dunnet correction for multiple comparison; *p < 0.05.