Fig. 4
Dual-κ B cells upregulate several T cell co-stimulatory receptors. a Representative MHCII I-Ak expression on single-κ (shaded gray) or dual-κ (black line) CD19+ B cells gated as in Supplementary Fig. 1a, b. b Quantification of MHCII described in a. c MHCII expression on dual-κ relative to single-κ FO and MZ B cells (gated as in Supplementary Fig. 6a), and plasmablasts (PB, gated as in Supplementary Fig. 1a, b). Data in b, c are pooled from two independent experiments (N = 7 total) using 13–15-wk-old MRL/lpr-Igkm/h mice. d IL-21R transcripts per million (TPM) in single or dual-κ FO and MZ B cells analyzed by RNAseq (described in Fig. 2). Data are from three independent biological replicates analyzed in one experiment. e Representative analysis of IL-21R expression on CD19+ single-κ or dual-κ B cells (gated as in Supplementary Fig. 1a, b) showing frequencies of IL-21R+ cells. IL-21R knockout splenocytes (inset plot) were used to set gates. f Frequencies of IL-21R+ cells as fold change relative to single-κ cells, analyzed as described in panel (e). g Relative MFI of IL-21R on IL-21R+ B cells from analyses in e, f. Data in f, g were combined from three independent experiments (N = 10 13–14-wk-old MRL/lpr-Igkm/h mice). h Representative analyses of indicated co-receptors on CD19+ single-κ (shaded gray) or dual-κ (black line) B cells gated as in Supplementary Fig. 5a, top row. i Expression (MFI) of indicated surface proteins analyzed as in panel (h) on dual-κ cells as a fold change relative to single-κ cells. CD40 is shown for total or CD40+ cells. Data were combined from two independent experiments (N = 10–14 13–16-wk-old MRL/lpr-Igkm/h mice). One CD80 dual-κ point (10.05 value) is outside the scale. j Representative analysis of MRL/lpr-Igkm/h GC B cells within CD19+Igκ+ cells gated as in Supplementary Fig. 1a,b. k Frequency of GC single or dual-κ B cells described in panel (j). Data were combined from three independent experiments (N = 9). **P < 0.01, ***P < 0.001, ****P < 0.0001; n.s., not significant. Significance was assessed by Student’s t- or Mann–Whitney tests. Bar graphs report SEM and symbols represent individual mice (besides in panel d)
