Phenotypes of human blood and tissue B10 cells ex vivo and B10 + B10pro cells after in vitro culture. (A) Representative cell surface phenotype of blood B cells cultured with LPS + PIB for 5 hours. (B) Representative cell surface phenotype of blood B10 + B10pro cells after stimulation with CD40L + LPS for 48 hours with PIB added during the final 5 hours of culture. (C) Representative cell surface phenotype of spleen B10 cells cultured with CpG + PIB for 5 hours. (D) Representative cell surface phenotype of spleen B10 + B10pro cells after stimulation with CD40L + CpG for 48 hours with PIB added during the final 5 hours of culture. (A-D) Cultured cells were stained for viability and cell surface molecule expression, permeabilized, stained with anti–IL-10 mAb, and analyzed by flow cytometry. Representative cell surface molecule expression by IL-10⁺ (thick line) and IL10⁻ (thin line) CD19⁺ B cells from 3 persons. Shaded histograms represent isotype-matched control mAb staining.