CD34+DNAMbrightCXCR4+ CLP mobilized in chronic inflammation

During the course of many chronic inflammatory disorders, a persistent Natural Killer (NK) cell derangement and activation is observed. While increased cell turnover is expected in these cases, little is known about whether and how NK cell homeostatic balance and numbers are maintained by CD34+ progenitor cells. Accordingly, we studied peripheral blood progenitor cells in patients with chronic inflammatory disorders including HIV-1, HCV, TB, COPD and PAPA. Cytometric analysis revealed the presence of a so far unidentified CD34+CD226(DNAM-1)brightCXCR4+ cell population in all these conditions. Further, microarray and PCR analysis showed transcriptional signatures typical of common lymphocyte precursors. Culture of CD34+CD226brightCXCR4+ cells gave rise to NK cell progenies characterized by high expression of activating receptors and mature function. Importantly, in healthy donors CD34+CD226brightCXCR4+ cells reside in bone marrow but do not circulate in peripheral blood and are absent in umbilical cord blood. The proportion of CD34+CD226brightCXCR4+ PBMC were found to correlate with the degree of inflammation, and represent an indicator of lymphoid cell turnover/reconstitution during chronic inflammation. Identification of CD34+CD226brightCXCR4+ circulation offers a novel view of emergency recruitment of cell-precursors upgrade our understanding and monitoring of chronic inflammatory conditions, and provide new insight of intermediate stages of NK cell development.

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