Molecular mechanisms underlying vascular and inflammatory cell network at endothelial and macrophage levels are still unclear. Here we found that microvascular inflammation associates with changes in Notch signaling at endothelium/monocyte interface including loss of endothelial Notch4 and the acquisition of the Notch ligand Dll4 in both cell types. We showed that endothelial DLL4 induces circulating monocytes to polarize into a M1-type pro-inflammatory macrophages (CD40highCD64highCD200Rlow HLADRlowCD11blow) eliciting the production of IL-6. Dll4 and IL-6 are both Notch-dependent and are required for macrophage polarization through selective down and upregulation of M2and M1-type markers, respectively. Subsequently, we investigated the ability of DLL4 to interfere with M2 polarization. We found that DLL4 triggers a specific alteration of the IL-4 induced M2 phenotype through a significant inhibition of M2 markers (CD11b, CD206, CD200R). DLL4 also induces caspase3/7-dependent apoptosis specifically in M2 differentiating macrophages while DLL1 had no effect. DLL4 signals via Notch1 and DLL4mediated apoptosis is Notch-dependent. Fully differentiated M2 macrophages became resistant to DLL4 action. DLL4 upregulates gene expression, upon M2 upon differentiation, affecting the Notch pattern (Notch1, 3, Jag1) and activity (Hes1), transcription (IRF5, STAT1) that associates with decrease in Akt but not STAT6 phosphorylation. In conclusion, our findings reveal an interplay between DLL4/Notch and IL-6/IL-6R or IL-4/IL-4R signaling pathways supporting M1 differentiation and impairing M2 differentiation via apoptosis.