CD23hi cells and IL6+ cells are derived from CD27+ memory B cells. A. PBMC were FACS-sorted into CD27+ (memory) and CD27- (naïve) B cells. Sorting strategy and purity of cells after sorting are shown. B. Sorted CD27+ and CD27- B cells were exposed to EBV. Cells were harvested on day 5 and examined for expression of CD23 (FITC) and intracellular IL6 (APC) by flow cytometry. Percentages represent IL6+ or CD23hi cells of CD27+ or CD27- B cells.