Fig. 3
T cells responses in spleen and cervical lymph nodes (CLNs). BALB/c mice were immunized by 3R-NC + KFDi.n and 3R-NC + ALi.m 3 times at 3 weeks interval (n = 5 mice per group). T cell responses were tested at day 10 post 3rd immunization. a 1.25 × 105 of positive selected CD4+ T cells were mixed with 7.5 × 105 naïve splenocyte as antigen presenting cells, and stimulated with or without RBD peptides. RBD-specific IFN-γ secretions were indicated by the mock (unstim) background-normalized spots (n = 4 mice per group). b, c ELISPOT tested the RBD peptides stimulated IFN-γ, IL-17 and IL-5 secretion by cells of spleens and CLNs. d, f Percentages of Tfh in CD4+ T cells of CLNs and spleens. e, g IL-21, IFN-γ and IL-17 secretion potential of Tfh in CLNs and spleens post non-specific stimulation. h Immune-staining of IL-17 (green), plasma cell marker CD138 (red) and cell nuclei (DAPI, blue) in spleens. The co-localization of IL-17 with CD138 were labeled by pink arrow. i Correlation of RBD-specific Th17 responses with the RBD-specific IgG and IgA response in mice of 3R-NC + KFDi.n and 3R-NC + ALi.m groups at day 10 post the 3rd immunization. The 95% confidence interval is indicated by dotted lines. Data are represented as mean ± SEM and are representative of two independent experiments. Groups were compared using one-way ANOVA except in (i). *p < 0.05; **p < 0.01; ***p < 0.001; ns non-significant
