Platelets and skin disorders

Recent accumulating evidence indicates that platelets act as effector cells in initiating and modulating inflammatory and immune responses in various organs including the skin. On activation in response to various factors such as chemokines and microbial toxins, platelets express adhesive and immune receptors such as P-selectin and Toll-like receptors on their surface and release soluble mediators such as chemokines, cytokines, and antimicrobial peptides. In patients with inflammatory skin disorders such as atopic dermatitis and psoriasis, platelets circulate in an activated state, and the degree of platelet activation correlates with disease severity. Platelets are deeply involved in the pathogenesis of several inflammatory skin disorders such as atopic dermatitis, contact dermatitis, psoriasis, urticaria, and infectious diseases via formation of platelet-leukocyte complexes, releasing chemotactic factors, inhibiting monocytic apoptosis, inducing neutrophil phagocytosis, promoting allergic sensitization, and releasing antimicrobial peptides.