<p>KIRnegNKG2Aneg cells comprise a distinct, phenotypically mature but functionally hyporesponsive subset of circulating bulk NK cells. (A) Representative flow cytometric contour plots (n=3) illustrate intracellular KIR and NKG2A expression on steady-state KIRpos and/or NKG2Apos (top panels) and KIRnegNKG2Aneg CD3negCD56pos NK cells (bottom panels). Antibody clones are shown in parenthesis. (B) Both KIRpos and/or NKG2Apos (shaded historgrams) and KIRnegNKG2Aneg cells (unshaded histograms) have a phenotypically mature surface phenotype. One representative experiment out of three is shown. Functional competence is compared between these two NK subsets based on (C) CD107a expression to detect cytotoxic degranulation (mean {plus minus} SD; n=5) and (D) intracellular IFN-gamma secretion (mean {plus minus} SD; n=5) after exposure to the NK sensitive LCL 721.221 cell line. **p=0.001-0.01; ***p<0.001.</p>
ARTICLE ABSTRACT
A functionally responsive natural killer (NK)–cell repertoire requires the acquisition of inhibitory NKG2A and killer immunoglobulin-like receptors (KIR) through pathways that remain undefined. Functional donor NK cells expressing KIRs for non-self class I MHC ligands contribute to a positive outcome after allogeneic hematopoietic stem cell transplantation (alloHSCT) by targeting HLA-matched recipient leukemic cells. Insofar as circulating donor conventional dendritic cells (DC) reconstitute with comparable kinetics with donor NK cells after alloHSCT, we used hyporesponsive KIRnegNKG2Aneg precursor cells to evaluate how specific DC subtypes generate a functionally active NK-cell repertoire. Both monocyte-derived DCs (moDC) and Langerhans-type DCs (LC) induce KIRnegNKG2Aneg precursor cells to express the inhibitory receptors NKG2A and KIR, without requiring cell proliferation. Poly(I:C)-matured moDCs significantly augmented the expression of NKG2A, but not KIR, in an IL12p70-dependent manner. Although all DC-stimulated KIRnegNKG2Aneg cells were able to acquire cytolytic activity against class I MHC-negative targets, the ability to secrete IFNγ was restricted to cells that were stimulated by IL12p70-producing, poly(I:C)-matured moDCs. This critical ability of poly(I:C)-matured moDCs to provide IL12p70 to developing KIRnegNKG2Aneg precursors results in a dominant, multifunctional, NKG2Apos NK-cell population that is capable of both cytolysis and IFNγ production. Poly(I:C)-matured moDCs are, therefore, the most effective conventional DC subtype for generating a functionally competent NK-cell repertoire by an IL12p70-dependent mechanism. Cancer Immunol Res; 2(10); 1000–10. ©2014 AACR.
