B cells were purified (90–95%) by negative selection with single-cell splenocyte suspensions by using biotinylated anti-Thy1.2 mAb followed by streptavidin-conjugated microbeads (BD Pharmingen). In brief, 0.75 × 106 cells/ml were cultured in 3 ml of RPMI 1640 medium (Life Technologies, no. 23400–021) in a six-well cell culture plate (Peak Serum, no. TR5000), supplemented with recombinant mouse BAFF (10 ng/ml). B cells were activated and plasma cell differentiation was stimulated using anti-CD40 (BD Biosciences, no. 553788) (1 μg/ml) or LPS (Sigma-Aldrich, L2630) (1 μg/ml), supplemented with IL-4 (PeproTech, no. 214–14) (10 ng/ml) and IL-5 (PeproTech, no. 215–15) (10 ng/ml) as indicated. RBN012579 was dissolved in 100% DMSO for stock solutions (1 mM; 368 μg/ml). Based on experimental data later reported in Schenkel et al. (33 (link)) (e.g., the section “Biochemical and pharmacokinetic characterization of RBN012759,” the Methods section, and legends to figures 4 and 5), cultures were treated with either DMSO or PARP14i (1 or 0.33 μM RBN012759), added once daily. Cultures were harvested and counted on day 5; supernatants were collected for ELISA to quantify relative levels of Ab (IgG1, IgG2a, and IgE) as described (14 (link)).