G-CSF-mobilized CD34+ cells cultured in interleukin-2 and stem cell factor generate a phenotypically novel monocyte

Open Access
Publisher Website
Google Scholar
Abstract
To study the early stages of development from stem cells of the CD56+ cell population [which includes natural killer (NK) cells], granulocyte‐colony stimulating factor‐mobilized peripheral blood CD34+ cells from healthy donors were sorted to >99% purity and cultured in the presence of stem cell factor and interleukin (IL)‐2. After 3 weeks in culture, the majority of cells acquired CD33, with or without human leukocyte antigen‐DR and CD14. In 20 stem cell donors tested, 8.7 ± 8.8% of cells were CD56+. Two major CD56+ subsets were identified: CD56bright, mainly CD33− cells (7±10%, n=11) with large, granular lymphocyte morphology, and CD56dim, mainly CD33+ (2.5±2, n=11) cells with macrophage morphology. The CD56bright population had cytoplasmic granzyme A but lacked killer inhibitory receptor, suggesting they were immature NK cells. The CD56dim, CD33+, population lacked NK markers. They may represent a minor subset of normal monocytes at a developmental stage comparable with the rare CD56+ CD33+ hybrid myeloid/NK cell leukemia. Consistent with a monocyte nature, CD56dimCD33+ proliferated and produced a variety of cytokines upon lipopolysaccharide stimulation, including IL‐8, IL‐6, monocyte chemoattractant protein‐1, and macrophage‐derived chemokine but not interferon‐γ. In a short‐term cytotoxicity assay, they failed to kill but powerfully inhibited the proliferation of the NK‐resistant cell line P815. The generation of CD56+ cells was negatively regulated by hyaluronic acid and IL‐4, indicating that extracellular matrix may play an important role in the commitment of CD34+ cells into CD56 myeloid and lymphoid lineages.
Funding Information
  • Cell Processing Section, Clinical Center, NIH (CD34+)
  • NHLBI, Hematology Branch, NIH