Increased apoptosis in human B cells when treated with R788. (A) Representative flow plots of human PBMCs with or without cGVHD. Consistent with previous work,³⁶  unmanipulated, untreated cGVHD B cells had superior survival compared with B cells from patients without disease. PBMCs from patients without cGVHD (n = 6, open circles) and with cGVHD (n = 6, filled squares) treated with R406 (0, 0.01, and 0.1 μM) as indicated for 48 hours. Apoptotic B cells were defined as CD19⁺ Annexin V⁺ 7AAD⁻ cells (B) or as CD19⁻ non–B cells (C). Fold increase in apoptosis by R406 divided by phosphate-buffered saline is depicted. Data are median ± range pooled from 2 independent experiments. *P < .5; **P < .01; ***P < .001. n.s., not significant.