B10-cell regulation of innate immunity. (A) B10 cell effects on mitogen-stimulated T-cell cytokine production. Purified blood CD24^hiCD27⁺ or CD24^lowCD27⁻ B cells were stimulated with CD40L plus CpG for 24 hours, isolated, and then cultured with CD3 mAb-stimulated CD4⁺ T cells for 72 hours. After PMA plus ionomycin stimulation, CD4⁺ T-cell TNF-α expression was assessed by flow cytometry (heavy lines). CD4⁺ T cells cultured alone are shown as positive controls (thin lines). Background cell staining using unstimulated T cells is shown (shaded lines). (B) B10 cells regulate monocyte cytokine production. Purified blood CD24^hiCD27⁺ or CD24^lowCD27⁻ B cells were stimulated with CD40L plus CpG for 24 hours and were cultured with blood monocytes for 20 hours before cytoplasmic TNF-α expression by CD14⁺ monocytes was assessed after 4 hours of LPS stimulation (heavy lines). Anti–IL-10 mAb was added to some cultures as indicated (dashed lines). Monocytes cultured alone are shown as positive controls (thin lines), with background cell staining using unstimulated monocytes shown (shaded lines). (A-B) Results represent those obtained in more than or equal to 2 independent experiments.