Fig. 3: Lymph node egress is necessary to generate anamnestic mucosal IgA responses.
a, Schematic of the experimental setup showing C57BL/6J mice i.m. primed with mRNA–LNPs at day 0, i.n. boosted with an unadjuvanted SARS-CoV-2 spike protein at day 14 post-priming, followed by treatment i.p. with PBS or FTY720 every other day, starting at day 14 (treatment 1), 16 (treatment 2) or 18 (treatment 3) after intramuscular priming, and lung, BALF and serum collection at day 21 after an intramuscular boost. b, Representative flow cytometry plots and number of extravascular total and RBD-specific IgA+ ASCs in the lungs of naive C57BL/6J mice (D0, n = 12); P + S mice treated with PBS (D21P+S, n = 13) or P + S mice treated with FTY720 at day 14 (D21T1, n = 10); day 16 (D21T2, n = 9); P + S day 18 (D21T3, n = 9) analyzed by flow cytometry at day 21 after intranasal priming as in a. c, ELISA measurements of SARS-CoV-2 S1-specific IgA and IgG in the BALF and serum from mice as in b. Data are the mean ± s.e.m. The statistical significance was calculated using one-way ANOVA (b,c). Tukey’s multiple comparisons were performed: *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. Data were pooled from three independent experiments (b,c). Values indicated as zero show the absence of detectable cells (b).
