Fig. 1: Characterization of antibody-secreting cell subsets in BCMA-KOΔ3 mice.

A Schematic illustration of the genetic locus of BCMA-KOΔ3 mice. BCMA:Tom mice with loxP sites flanking exon 3 of the BCMA-encoding Tnfrsf17 gene and the IRES-tdTomato cassette were crossed to E2A-Cre mice, resulting in a germline deletion of exon 3. Exons are illustrated in gray boxes, and light gray boxes indicate 5’ and 3’ UTRs. B Flow cytometric analysis of BCMA cell surface abundance on splenic ASCs after y-secretase inhibitor (DAPT) treatment using the anti-BCMA antibody clone 25C2. Splenic single-cell suspensions were cultured for 18 h with 1 µM DAPT or DMSO solvent control (Ctrl). C Representative gating strategy to quantify frequencies of CD138⁺TACI⁺ ASCs, ASC subsets P0 (B220^hiCD19^hi), P1 (B220⁺CD19⁺), P2 (B220⁻CD19⁺), and P3 (B220⁻CD19⁻) and IgH-chain isotype distribution in the bone marrow (BM) ASCs. Double negative (DN) ASCs contain mostly IgG ASCs^10,17. n = 8 mice per group from 3 independent experiments. Bar diagrams show mean and SD with each dot indicating one mouse. D, E Transcriptome analysis of bone marrow and splenic ASCs isolated from non-immunized BCMA-KOΔ3 and wildtype mice (WT). Principal component analysis (D) visualizes sample similarities; differential gene expression is visualized in the MA plot (E). In BCMA-KOΔ3 ASCs, no upregulated genes were detected, and the only downregulated gene (Tnfrsf17) is colored in blue. Statistical analysis in (C) was performed with a two-tailed unpaired t-test to compare total ASC numbers. Comparisons of ASC subsets were conducted by two-way ANOVA with Šídák’s correction for multiple comparisons. Exact p-values, mouse sex, and ages are provided in the Source Data file. ns not significant, ASC antibody-secreting cell, PC principal component.