Expression of the IL-23/Th17 pathway in lesions of hidradenitis suppurativa

Background: Hidradenitis suppurativa is a debilitating chronic disease primarily affecting intertriginous skin of the axillae, perineum, and inframammary regions. The pathogenesis of this inflammatory disease is still poorly understood. Recently, increased attention has been paid to the role of the immune system. Objective: Since the interleukin 12 (IL-12)/T helper 1 (Th1) and the IL-23/Th17 pathways are believed to be crucially involved in the pathogenesis of multiple chronic inflammatory diseases, we investigated the expression and cellular source of 1L-12, IL-23, and IL-17 in hidradenitis suppurativa. Methods: Ten patients with hidradenitis suppurativa were included in the study. Tissue samples were obtained from lesional skin and compared with healthy skin as a control. Expression of IL-12, IL-23, and IL-17 was analyzed by semiquantitative real-time polymerase chain reaction and immunohistochemistry, and the cellular source of these cytokines was determined by double immunofluorescence. Results: IL-12 and IL-23 were found to be abundantly expressed by macrophages infiltrating papillary and reticular dermis of lesional skin. In accordance with the high expression of IL-23 and its important role in the development of T helper 17 (Th17) cells, IL-17-producing T helper cells were found to distinctly infiltrate lesional dermis. Limitations: The sample size was small. Conclusions: Our findings suggest that the IL-23/Th17 pathway is expressed in hidradenitis suppurativa and further support involvement of the immune system. Moreover, targeting the IL-12/IL-23-common subunit p40 with novel monoclonal antibodies may represent a new option for the treatment of this recalcitrant disease. (J Am Acad Dennatol 2011;65:790-8.)