Rapid Induction of CD40 on a Subset of Granulocyte Colony-Stimulating Factor–Mobilized CD34+ Blood Cells Identifies Myeloid Committed Progenitors and Permits Selection of Nonimmunogenic CD40− Progenitor Cells

Abstract

CD40 antigen is a costimulatory molecule highly expressed on dendritic cells (DC) and activated B cells, which induces T-cell proliferation through the binding with CD40L receptor. In this study, we evaluated CD40 expression on normal CD34+blood cells and functionally characterized CD34+CD40+ and CD34+CD40− cell subsets. CD40, CD80, and CD86 antigens were constitutively expressed on 3.2% ± 4.5%, 0%, and 1.8% ± 1.2% CD34+ blood cells, respectively. However, after 24 hours in liquid culture with medium alone, or with tumor-necrosis-factor- (TNF-), or with allogeneic mononuclear cells 10.8% ± 3.8%, 75.3% ± 15.0% and 53.7% ± 17.0% CD34+ blood cells, respectively, became CD40+. After incubation for 24 hours with TNF- CD34+CD40+ blood cells expressed only myeloid markers and contained less than 5% CD86+ and CD80+ cells. Also, a 24-hour priming with TNF- or ligation of CD40 significantly increased the CD34+ blood cells alloantigen presenting function. Finally, purified CD34+CD40+ blood cells stimulated an alloreactive T-cell response in MLC, were enriched in granulocytic, monocytic, and dendritic precursors, and generated high numbers of DC in 11-14 d liquid cultures with GM-CSF, SCF, TNF- and FLT-3L. In contrast, CD34+CD40− cells were poorly immunogenic, contained committed granulocytic and erythroid precursors and early progenitors, and differentiated poorly toward the DC lineage. In conclusion, a short incubation with TNF- allows the selection of CD40+ blood progenitors, which may be a useful source of DC precursors for antitumor vaccine studies, and also a CD34+CD40− blood cell fraction that could be exploited in innovative strategies of allogeneic transplantation across HLA barriers.