Phenotypic changes during the differentiation process of plasmablasts into plasma cells in vitro. (A) Analysis of CD138 and CD19 expression in double staining with anti-CD138-biotin-streptavidin-PECy5 and anti-CD19-PE MoAbs and analysis of CD38 expression in simple staining during time-course differentiation (RP5). At day 0, CD138⁺ and CD20⁺ cells were removed as described in Materials and Methods. The percentage of positive cells and the fluorescence intensity ratio (r) are indicated. Intracellular light-chain staining was performed, as described in Materials and Methods. The histograms show the fluorescence profiles for λ or κ expression as indicated. (B) Analysis of CD49e expression at day 0 or 7 by double staining with anti-CD49e MoAb and anti-CD19-FITC MoAb or anti-CD38-FITC MoAb, respectively (RP5). (C) Analysis of the expression of HLA-DR by simple staining with anti-HLA-DR-PE MoAb. Overlay histograms represent the immunofluorescence of HLA-DR and the control. (Left) RP8; (right) RP5.