TACI signaling in resting cells leads to a plasma-cell phenotype through plasma-cell gene program activation. (A) Representative FACS results showing CD19 and CD138 surface expression on resting A20, A20 GFP, and A20 TACI-expressing cells. Numbers indicate percentage of positive cells. (B) Flow cytometry analysis of surface CD19, CD138, and IgG on resting cells. Error bars represent standard deviation compared to A20 parental cell line, GFP, and S194X TACI-expressing cells (Mann-Whitney U test; **P < .01; ***P < .0001). Data summarize at least 3 independent experiments. (C) Resting A20 and A20 TACI-transduced cells were analyzed by transmission electron microscopy; >200 cells were assessed. Bar represents 2 μm. E, euchromatin; G, golgi; H, heterochromatin; M, mitochondria; N, nucleus; Nu, nucleolus; RER, rough endoplasmic reticulum. (D) qRT-PCR of Bcl6, Prdm1, Pax5, Xbp1, and Aicda mRNA expression levels. Results are normalized to Actb mRNA and represented as relative expression. Data are from 5 independent experiments; error bars represent standard error of the mean. *P < .05, 2-tailed unpaired Student t test.