Interleukin-21 induces the differentiation of human umbilical cord blood CD34^-lineage^-cells into pseudomature lytic NK cells

• Main Authors: Scambia Giovanni, Corallo Maria, Procoli Annabella, Mariotti Andrea, Bonanno Giuseppina, Pierelli Luca, Rutella Sergio
• Format: Article
• Language: English
• Published: BMC 2009-08-01
• Series: BMC Immunology
• Online Access: http://www.biomedcentral.com/1471-2172/10/46

<p>Abstract</p> <p>Background</p> <p>Umbilical cord blood (UCB) is enriched with transplantable CD34⁺cells. In addition to CD34-expressing haematopoietic stem cells (HSC), human UCB contains a rare population of CD34^-lineage^-cells endowed with the ability to differentiate along the T/NK pathway in response to interleukin (IL)-15 and a stromal cell support. IL-21 is a crucial regulator of NK cell function, whose influence on IL-15-induced differentiation of CD34^-lineage^-cells has not been investigated previously. The present study was designed and conducted to address whether IL-21 might replace the stromal cell requirements and foster the IL-15-induced NK differentiation of human UCB CD34^-lineage^-cells.</p> <p>Results</p> <p>CD34^-lineage^-cells were maintained in liquid culture with Flt3-L and SCF, with the addition of IL-15 and IL-21, either alone or in combination. Cultures were established in the absence of feeder cells or serum supplementation. Cytokine-treated cells were used to evaluate cell surface phenotype, expression of molecular determinants of lymphoid/NK cell differentiation, secretion of IFN-γ, GM-CSF, TNF-α and CCL3/MIP-1α, and cytolytic activity against NK-sensitive tumour cell targets. CD34^-lineage^-cells proliferated vigorously in response to IL-15 and IL-21 but not to IL-21 alone, and up-regulated phosphorylated Stat1 and Stat3 proteins. CD34^-lineage^-cells expanded by IL-21 in combination with IL-15 acquired lymphoid morphology and killer-cell immunoglobulin-like receptor (KIR)^-CD56⁺CD16^-/+phenotype, consistent with pseudo-mature NK cells. IL-21/IL-15-differentiated cells expressed high levels of mRNA for Bcl-2, GATA-3 and Id2, a master switch required for NK-cell development, and harboured un-rearranged TCRγ genes. From a functional standpoint, IL-21/IL-15-treated cells secreted copious amounts of IFN-γ, GM-CSF and CCL3/MIP-1α, and expressed cell surface CD107a upon contact with NK-sensitive tumour targets, a measure of exocytosis of NK secretory granules.</p> <p>Conclusion</p> <p>This study underpins a novel role for IL-21 in the differentiation of pseudo-mature lytic NK cells in a synergistic context with IL-15, and identifies a potential strategy to expand functional NK cells for immunotherapy.</p>