Chronic spontaneous urticaria (CSU) is a common skin disorder characterized by an almost daily recurrence of wheal and flare with itch for more than 6 weeks, in association with the release of stored inflammatory mediators, such as histamine, from skin mast cells and/or peripheral basophils. The involvement of the extrinsic coagulation cascade triggered by tissue factor (TF) and complement factors, such as C3a and C5a, has been implied in the pathogenesis of CSU. However, it has been unclear how the TF-triggered coagulation pathway and complement factors induce the activation of skin mast cells and peripheral basophils in patients with CSU. In this review, we focus on the role of vascular endothelial cells, leukocytes, extrinsic coagulation factors and complement components on TF-induced activation of skin mast cells and peripheral basophils followed by the edema formation clinically recognized as urticaria. These findings suggest that medications targeting activated coagulation factors and/or complement components may represent new and effective treatments for patients with severe and refractory CSU.
Keywords: activated complement factor 5 (C5a); chronic spontaneous urticaria (CSU); coagulation factors; complement components; endothelial cells; leukocytes; mast cells; protease activated receptor (PAR).