Fig. 4: SpFN + ALFQ vaccinated mice elicited higher frequencies of S-2P protein-specific naive B cells and S-2P protein-specific-IgG1⁺ memory B cells (MBCs) in the spleen following priming vaccinations.

Spleens from vaccinated (n = 6 in each group) and naive (n = 2) mice were collected on week 4. Flow cytometry analysis was performed to determine the frequencies of naive B cells and MBCs. a Frequency of naive B (CD19⁺B220⁺IgD^hi) cells in all the three groups. b Frequency of S-2P protein-specific naive B (CD19⁺B220⁺IgD^hi) cells. c IgG-1⁺CD38⁺MBCs (IgD^-Fas^-CD19⁺B220⁺) and d S-2P protein-specific IgG-1⁺MBCs are shown. The data are represented as bar graphs (Mean±SEM) and each dot represents the data from an individual spleen. The right panels show the representative contour flow plots for each subset. The flow panel and the gating strategy for the respective subsets are shown in Supplementary Table 4 and Supplementary Figs. 4 and 5a, respectively. The statistical differences between the two vaccinated groups were evaluated by Mann–Whitney U-test with P ≤ 0.05 considered as significant.