Possible roles of basophils in chronic itch

Basophils are blood granulocytes and normally constitute <1% of blood peripheral leucocytes. Basophils share some morphological and functional similarities with mast cells, and basophils were once regarded as redundant and negligible circulating mast cells. However, recent studies reveal the indispensable roles of basophils in various diseases, including allergic and pruritic diseases. Basophils may be involved in itch through the mediation of a Th2 immune response, interaction with other cells in the skin and secretion of a wide variety of itch-related mediators, for example histamine, cytokines and chemokines (IL-4, IL-13, IL-31 and TSLP), proteases (cathepsin S), prostaglandins (PGE2 and PGD2), substance P and platelet-activating factor. Not only pruritic skin diseases (eg, atopic dermatitis, irritant contact dermatitis, chronic urticaria, prurigo, papulo-erythroderma of Ofuji, eosinophilic pustular folliculitis, scabies, tick bites and bullous pemphigoid) but also pruritic systemic diseases (eg, primary sclerosing cholangitis and polycythemia vera) may be affected by basophils.

IL-31 and IL-33 circulating levels in allergic contact dermatitis

Enhanced IL-31 expression in skin biopsies is present in allergic contact dermatitis (ACD). IL-33 expression is induced in keratinocytes and in skin of ACD patients. This overexpression is present in both allergic and irritant conditions. The aim of this work was to test the systemic involvement of IL-31 and IL-33 in ACD. IL-31 levels were significantly higher in patients than in controls. IL-33 serum levels, on the contrary, were similar in patients and controls. This work shows a possible systemic involvement of IL-31 and the absence of a systemic involvement of IL-33 in ACD. IL-31 levels do not seem related to the allergen involved, and did not change on the strength of the allergen involved. More likely, IL-31 levels are related to the itch. IL-33, instead, is secreted from damaged or inflamed tissue and might function as an early warning system at the site of skin damage. In the future, IL-31 could be a possible therapeutic target of all pruritic skin diseases resistant to conventional therapies.