ATRA treatment of B cells from active cGVHD patients enhances genes involved in B-cell maturation. (A) B cells from active cGVHD patients (n = 4) were treated with ATRA (0.1 μM) or vehicle alone for 24 hours. The B cells were harvested, total RNA isolated, and real-time qPCR analysis performed to assess the expression levels of genes of interest. P values were determined using a paired Student t test (*P < .05; **P < .01). (B-C) Purified B cells from active cGVHD patients were plated in medium in the presence of ATRA (0.1 μM) or DMSO vehicle control. Following an initial culture period of 30 minutes, CpG (1 μg/mL) or anti-IgM Ab (0.625 μg/mL) were added alone or in combination. The cells were cultured for 72 hours, harvested, and flow cytometry analysis performed to assess Ki-67 and CD19 expression (B), as well as relative cell size by FSC (C). In panel B, the large gates with numbers outside indicate the frequency of Ki-67⁺ B cells, and the small gates (arrows) with numbers inside represent the frequency of proliferating, CD19^low B cells.