Fluorescence analysis of CD5 and CD23 expression of human PB B-cell subsets. CD19⁺-enriched B cells (96% and 98% purity, respectively) were stained with anti-IgM-PE, IgD-CyChrome, and anti-CD5-FITC or anti-CD23-FITC. (Top) Windows were set around the IgM^+/++IgD⁺, IgM⁺⁺IgD⁻, and IgM⁻IgD⁻ (mostly representing IgG⁺ and IgA⁺ cells) populations and analyzed for CD5 and CD23 staining within the respective fractions. (Histograms) CD5 and CD23 stainings of the CD19-enriched cell suspension (upper row) and the corresponding analyses of the B-cell subsets.