Induction of CD38⁺CD138⁻cell populations by activation of peripheral blood B lymphocytes.

E cells were activated for 7 days with CD154-transfected 300-19 cells in the presence of SAC (1/5000) and 10 ng/mL IL-4. (A) Analysis of cell size and granulosity with the use of a cytometer according to forward scatter/side scatter (FS/SS). We could clearly define 2 populations of nongranular small B lymphocytes (SBL) and large B lymphocytes (LBL); cell populations with high granulosity included cells positive for propidium iodine staining. (B) Expression of surface markers in LBL and SBL populations identified with the use of indirect immunofluorescence with specific mAbs and flow cytometry analysis. Dark histograms represent the fluorescence obtained with negative control isotype–matched mAbs. Top panels: SBL population. Bottom panels: LBL population. All experimental procedures are described in “Materials and Methods.” Both LBL and SBL populations were negative for CD138 (not shown).