Fig 1: SLE patient T-bethi BDN cells rapidly differentiate in ASCs in the absence of BCR stimulation.(a–d) ASC generation from SLE BN cells requires early but transient BCR activation. Cartoon (a) depicting in vitro stimulation conditions to activate sort-purified T-betlo BN cells from SLE patients. BN cells were stimulated for 3 days with R848, cytokines (IFN?, IL-2, IL-21, BAFF) ± anti-Ig (Step 1) and then washed and recultured for an additional 3 days with the same stimuli ± anti-Ig (Step 2). Cells were analyzed by flow cytometry on day 6 (b–d). Phenotypic characterization (b) of IgDnegCD27neg BDN cells in cultures containing anti-Ig for all 6 days showing expression of T-bet, CD11c, FcRL5, CD21 and CXCR5 by the T-bethi BDN subset. The frequency (c) and number (d) of CD38hiCD27+ ASCs in cultures lacking anti-Ig (-,-), containing anti-Ig for all 6 days (+,+) or exposed to anti-Ig for the first 3 days only (+,-). (e) SLE patient T-bethi BDN cells rapidly differentiate in ASCs. Purified SLE B cell subsets (T-betlo BN, T-betlo CD11cnegCXCR5+ CD27negIgDneg DN1 memory cells, T-betlo CD27+ memory B cells (Bmem) and T-bethi CD11c+CXCR5neg DN2 cells) were stimulated with cytokines (IFN?, IL-21, IL-2, BAFF) and R848 for 2.5 days then counted and transferred to anti-IgG ELISPOT plates for 6 hr. The frequency of IgG ASCs derived from each B cell subset is shown. See Figure 8—figure supplement 1 for gating strategy to purify B cell subsets from SLE patients. Data shown in (c–d) are from a single SLE individual and are representative of 2 independent experiments. Data reported in (e) are representative of 3 independent experiments using B cells sorted from 3 different SLE donors. Statistical analyses were performed using one-way ANOVA with Tukey’s multiple comparison test (d–e). P values *<0.05, **<0.01, ***<0.001, ****<0.0001.