Fig. 2: Circulating memory cells are the source for mucosal recall responses.
a, Schematic of the experimental design showing CD45.2 C57BL/6J mice primed i.m. with mRNA–LNPs at day 0 surgically paired with CD45.1 naive mice at day 14, followed by an intranasal boost of either the CD45.1 naive or the CD45.2 primed mice of the parabiotic pair with SARS-CoV-2 spike protein at day 14 after surgery, and analysis of lungs and BALF at day 14 after booster i.n. b, Representative flow cytometry plots and frequency of host-derived cells among intravenous CD45+ cells in the lungs of a parabiosis pair boosted i.n. in either CD45.1 (n = 17) or CD45.2 (n = 15) mice analyzed by flow cytometry as in a. c–f, Representative flow cytometry plots (left) and number (right) of extravascular IV−CD44+Tet+CD4+ T cells (c) and IV−CD44+Tet+CD8+ T cells (e) and frequency of CD45.2+ cells among extravascular IV−CD44+Tet+CD4+ T cells (d) and IV−CD44+Tet+CD8+ T cells (f) in the lungs of CD45.1 and CD45.2 mice of a parabiosis pair as in b. g, Representative flow cytometry plots and extravascular RBD+IgA+ ASC numbers in the lungs of CD45.1 (n = 5) and CD45.2 (n = 5) mice of a parabiosis pair as in a. h, Frequency of CD45.2+ cells among extravascular IV−RBD+IgA+ ASCs in the lungs of CD45.1 and CD45.2 mice of a parabiosis pair as in g. i, ELISA measurements of SARS-CoV-2 S1-specific IgA and IgG in the BALF of CD45.1 and CD45.2 mice of a parabiosis pair as in b. Data are the mean ± s.e.m. The statistical significance was calculated using one-way ANOVA (b,i) or nonparametric Kruskal–Wallis test (c,e,g). Tukey’s multiple comparisons (b,i) and Dunn’s multiple comparisons (c,e,g) were performed: *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. Data were pooled from four (b–f) independent experiments or represent (g,h) an experiment. Values shown as zero indicate the absence of detectable cells (c,e,g).
