HCMV-controlling NKG2C⁺ NK cells originate from novel circulating inflammatory precursors

There is limited knowledge on the origin and development from CD34⁺ precursors of the ample spectrum of human natural killer (NK) cells, particularly of specialized NK subsets.

This study sought to characterize the NK-cell progeny of CD34⁺DNAM-1^brightCXCR4⁺ and of other precursors circulating in the peripheral blood of patients with chronic viral infections (eg, HIV, hepatitis C virus, cytomegalovirus reactivation).

Highly purified precursors were obtained by flow cytometric sorting and cultured in standard NK-cell differentiation media (ie, SCF, FLT3, IL-7, IL-15). Phenotypic and functional analyses on progenies were performed by multiparametric cytofluorimetric assays. Transcriptional signatures of NK-cell progenies were studied by microarray analysis. Inhibition of cytomegalovirus replication was studied by PCR.

Unlike conventional CD34⁺ precursors, Lin^-CD34⁺DNAM-1^brightCXCR4⁺ precursors from patients with chronic infection, rapidly differentiate into cytotoxic, IFN-γ-secreting CD94/NKG2C⁺KIR⁺CD57⁺ NK-cell progenies. An additional novel subset of common lymphocyte precursors was identified among Lin^-CD34^-CD56^-CD16⁺ cells and characterized by expression of CXCR4 and lack of perforin and CD94. Lin^-CD34^-CD56^-CD16⁺Perf^-CD94^-CXCR4⁺ precursors are also endowed with generation potential toward memory-like NKG2C⁺NK cells. Maturing NK-cell progenies mediated strong human cytomegalovirus-inhibiting activity. Microarray analysis confirmed a transcriptional signature compatible with NK-cell progenies and with maturing adaptive NK cells.

During viral infections, precursors of adaptive NK cells are released and circulate in the peripheral blood.