Characterization of transitional, memory, and naïve B subsets. (A–C) Definition of human B subsets including CD19+CD24hiCD38hiCD27− TrB cells, CD19+CD24+CD38+ CD27− naïve B cells, and CD19+CD24hiCD27+ memory B cells. (D) Representative overlay histograms comparing the strength of expression of CD20, CD10, and IgM between the TrB and mature naïve B cells (n=5).