From B cells to PCs. (A) Schematic representation of the 125 genes that were statistically differentially expressed between the 2 B-cell populations and the 3 PC populations with a ratio of mean expression greater than 2. Relevant genes that were statistically differentially expressed between B cells and PCs but with at least one ratio of mean expression less than or equal to 2 are indicated in parentheses. PBB indicates peripheral blood B cells; TBC, tonsil B cells; TPC, tonsil plasma cells; BMPC, bone marrow plasma cells; PPC, polyclonal plasmablastic cells. (B) Real-time PCR quantification of B-cell and PC transcription factors. cDNA obtained from 3 PBB cells, 3 PPCs, and 3 BMPCs were analyzed for PRDI-BF1, XBP-1, IRF-4, BSAP, SPIB, and ID3 expression using β₂-microglobulin as the normalization control. The data are expressed as the mean of the 3 samples tested and represent the ratio of value in PC–value in PBB cells.