Human plasmacytoid dendritic cells express the functional purinergic halo (CD39/CD73).

Plasmacytoid dendritic cells (pDCs) are a specialized DC subset mainly associated with sensing viral pathogens and high-type I interferon (IFN-I) release in response to toll-like receptor (TLR)-7 and TLR-9 signaling. Currently, pDC contribution to inflammatory responses is extensively described; nevertheless, their regulatory mechanisms require further investigation. CD39 and CD73 are ectoenzymes driving a shift from an ATP-proinflammatory milieu to an anti-inflammatory environment by converting ATP to adenosine. Although the regulatory function of the purinergic halo CD39/CD73 has been reported in some immune cells like regulatory T cells and conventional DCs, its presence in pDCs has not been examined. In this study, we uncover for the first time the expression and functionality of the purinergic halo in human blood pDCs. In healthy donors, CD39 was expressed in the cell surface of 14.0 ± 12.5% pDCs under steady-state conditions, while CD73 showed an intracellular location and was only expressed in 8.0 ± 2.2% of pDCs. Nevertheless, pDCs stimulation with a TLR-7 agonist (R848) induced increased surface expression of both molecules (43.3 ± 23.7% and 18.6 ± 9.3%, respectively), as well as high IFN-α secretion. Furthermore, exogenous ATP addition to R848-activated pDCs significantly increased adenosine generation. This effect was attributable to the superior CD73 expression and activity because blocking CD73 reduced adenosine production and improved pDC allostimulatory capabilities on CD4 + T cells. The functional expression of the purinergic halo in human pDCs described in this work opens new areas to investigate its participation in the regulatory pDC mechanisms in health and disease.

CRTAM is negatively regulated by ZEB1 in T cells.

T cell activation leads to the induction of genes that are required for appropriate immune responses. This includes CRTAM (Class-I MHC-restricted T cell associated molecule), a protein that plays a key role in T cell development, proliferation, and generating cell polarity during activation. We previously characterized the CRTAM promoter and described how AP-1 family members are important for inducing CRTAM expression upon antigenic activation. Here, we show that CRTAM is a molecular target for ZEB1 (zinc finger E-box-binding protein), a homeodomain/Zn finger transcription factor. Overexpression of ZEB1 repressed CRTAM promoter activity, as well as endogenous CRTAM levels in human T cells. ZEB1-mediated transcriptional repression was abolished when E-box-like elements in the CRTAM promoter are mutated. In summary, ZEB1 functions as a transcriptional repressor for the CRTAM gene in both non-stimulated and stimulated T cells, thereby modulating adaptive immune responses.