These results point to the role of reduced oxygenation to the pathogenesis of inflammatory disorders and/or autoimmune diseases, which are associated with over-expression of some of these receptors [26, 33, 43]. The influence of low pO2 on the expression profile of immune-related surface receptors has been previously documented in other monocytic lineage cells, such as primary monocytes exposed to short-term hypoxia [36] and monocyte-derived mDCs generated under long-term hypoxic Ponatinib conditions [18, 23], and the results reported here extend to iDCs this trend of response to hypoxia. However, different combinations

of receptor-encoding genes are expressed in these cell populations, suggesting that hypoxia may activate a specific transcriptional response in MP depending on their differentiation/maturation stage, which probably represents a mechanism of regulation of the amplitude and duration of inflammatory responses, and the challenge of future studies will be to validate these data in vivo. TREM-1 is one of the few hypoxia-inducible gene targets in H-iDCs shared

with H-mDCs and monocytes. TREM-1 mRNA expression is consistently expressed on H-iDCs generated from different LDE225 in vivo donors but not on the normoxic counterpart, confirming previous evidence of TREM-1 downregulation during monocyte to iDCs differentiation under normoxic conditions [28, 30]. mRNA induction is paralleled by expression of the membrane-bound receptor and its soluble form, detectable in several inflammatory disorders [29, 37, 44]. TREM-1 inducibility by hypoxia is reversible, because cell reoxygenation

results in marked decrease of the receptor supporting the role of low pO2 as a TREM-1 inducer in iDCs. In line with these findings, we provide Exoribonuclease evidence that the HIF/HRE system is implicated, at least in part, in TREM-1 gene inducibility by hypoxia. H-iDCs treatment with echinomycin, a known specific inhibitor of HIF-1 binding to HRE and transcriptional activity [39], downmodulates TREM-1 mRNA and surface protein levels. The potential contribution of other transcription factors, known to mediate hypoxia-dependent gene transactivation in myeloid cells [11, 17, 45], to the regulation of TREM-1 expression in H-iDCs is currently under investigation. These results suggest that TREM-1 expression in iDCs in vivo may vary dynamically with the degree of local tissue oxygenation, which is quite heterogeneous and rapidly fluctuating in diseased tissues [24], giving rise to distinct DC subsets potentially endowed with different functional properties TREM-1 is functionally active in H-iDCs, as demonstrated by the finding that TREM-1 cross-linking by an agonist mAb on H-iDCs increases surface expression of CXCR4 and CD86 and promotes that of CCR7 and CD83, which play a central role in T-cell migration and activation [46].