• M Tohyama, H Watanabe, S Murakami, Y Shirakata, K Sayama, M Iijima, and K Hashimoto.
• Department of Dermatology, Ehime University Graduate School of Medicine, Shitsukawa, Toon-city, Ehime 791-0295, Japan. tohm@m.ehime-u.ac.jp
• Br. J. Dermatol. 2012 Feb 1; 166 (2): 322-30.

BackgroundStevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are characterized by keratinocyte apoptosis and necrosis, resulting in epidermal detachment. Although monocytes abundantly infiltrate the epidermis in SJS/TEN skin lesions, the properties and functions of these cells have not been fully examined.ObjectivesTo determine the properties of monocytes infiltrating into the epidermis in SJS/TEN.MethodsImmunostaining of skin sections was performed to examine the membrane markers of monocytes infiltrating into skin lesions.ResultsImmunostaining of cryosections from 11 SJS/TEN skin lesions revealed numerous CD14+ monocytes located along the dermoepidermal junction and throughout the epidermis. The cells coexpressed CD16, CD11c and HLA-DR. CD14+ CD16+ cells were identified in very early lesions without epidermal damage, suggesting that their infiltration is a cause, rather than a result, of epidermal damage. Moreover, these cells expressed CD80, CD86 and CD137 ligand, indicative of their ability to facilitate the proliferation and cytotoxicity of CD8+ T cells. CD16+ cells infiltrating the epidermis and detected at the dermoepidermal junction were immunostained and counted in paraffin-embedded skin sections obtained from 47 patients with drug rash manifested as TEN, SJS, maculopapular-type rash or erythema multiform-type rash. The number of CD16+ monocytes infiltrating the epidermis increased significantly, depending on the grade of epidermal damage.ConclusionsThese findings suggest that the appearance of CD14+ CD16+ cells of monocyte lineage plays an important role in the epidermal damage associated with SJS/TEN, most probably by enhancing the cytotoxicity of CD8+ T cells.© 2011 The Authors. BJD © 2011 British Association of Dermatologists.

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