Fig. 3: P1, P2, and P4 B cells express IL-10 and PD-L1, but P2 and P4 B cells are more efficient than P1 B cells at suppressing T cell responses.

a, b Frequency of IL-10⁺ B cells in P1–P6 B cells (a) and the amount of IL-10 secreted by P1, P2, and P4 B cells (b). FACS-sorted blood B cells (P1–P6) of healthy subjects (N = 6) were incubated for 48 h with 2.5 µg/mL CpG-B before intracellular IL-10 staining. The amount of IL-10 in supernatant was measured by ELISA. Four independent experiments using cells from six healthy subjects (represented by individual dots) were performed. c, d Kinetics of the frequency of IL-10⁺ cells (c) and the amount of IL-10 secreted (d) overtime. Experiments were performed with the same number of cells plated for each indicated populations. Three independent experiments using cells from different healthy subjects (n = 5) were performed. e, f Representative FACS plots (e) and summarized data (f) for the frequency of IL-10⁺PD-L1⁺ B cells. Isotype antibody staining was performed using mixture of P1–P6 B cells. Five independent experiments using cells from different healthy subjects (n = 6) were performed. g–i Representative FACS data showing the suppression of CD4⁺ T cell proliferation by P1–P6 B cells (g). Summarized data of g from five independent experiments using cells from different healthy subjects (n = 6) (h). CD4⁺ T cell proliferation assay was performed with indicated numbers of B cells from different healthy subjects (n = 4) (i). Error bars are mean ± SD. P values were determined with one-way ANOVA with Holm–Sidak’s multiple comparisons test (a, b, f, and h) and two-way ANOVA with Dunnett’s multiple comparison test (c, d, and i).