Characterization and isolation of tonsillar B-cell subsets based on CD38/IgD/CD27 staining. (A) Tonsillar mononuclear cells were stained with PE-Cy5-conjugated anti-CD20 mAbs to enumerate the percentage of B cells in tonsils from chronic virus carriers (CCT) and IM patients (IMT). Purified B cells were triple-stained with PE-Cy5-conjugated anti-CD38, FITC-conjugated anti-IgD, and PE-conjugated anti-CD27 Abs to enumerate the percentages of CD38⁺ and CD38^hi cells, and from the CD38⁻ fraction, IgD⁺CD27⁻ naive, IgD⁻CD27⁺ isotype-switched memory and IgD⁺CD27⁺ nonswitched memory subsets. Median values for each group are shown by the horizontal bars; there were no statistical differences in the proportion of each subset between chronic carrier and IM tonsils. (B) Purified tonsillar B cells were separated into the 5 subsets shown in panel A using the indicated sort gates and the isolated B-cell populations subsequently reanalyzed to determine the sort purities. Shown are representative data from donor CCT8.