Differential susceptibility of normal human blood cells to CD47-induced cell death.

(A-B) Cord-blood CD34⁺ cells (stem cells) (n = 6), monocyte-derived iDCs (n = 4), resting and activated tonsillar B cells (n = 4), and peripheral T cells (n = 4) were stained for CD47 expression (B6H12 mAb) and analyzed by flow cytometry: isotype-control mAb (open histogram), CD47 mAb (shaded histogram). (A) Stem cells and iDCs were cultured in the absence or presence of immobilized CD47 mAbs (10 μg/mL) for 18 hours and double-stained with FITC-labeled annexin-V and PI. Shown are percent of viable cells (annexin-V⁻/PI⁻). (B) Resting T and B cells were left unstimulated or activated for 48 hours with plastic-coated anti-CD3 (3 μg/mL) or sCD40L (1 μg/mL) + IL-4 (10 ng/mL), respectively, and then cultured overnight in the absence or presence of immobilized CD47 mAbs. The mean percent of CD47-induced cell death, calculated as indicated in “Patients, materials, and methods” are shown.