69), such as in Behçet's syndrome (Refs 67, 68). Concomitantly, ROS can induce leucocyte recruitment via different complementary mechanisms: they can directly act as a chemoattractant for neutrophils and monocytes, mostly via upregulation of IL-8 (Ref. 70) and of monocyte chemotactic protein-1 (MCP-1) production, respectively (Ref. 71). Moreover, they can increase the expression of leucocyte adhesion molecule expression (such as platelet-endothelial cell adhesion molecules-1, PECAM-1) and promote leucocyte endothelial adhesion (Ref. 72). Here, PECAM1 is linked to Behcet disease.