Epidermal Langerhans cells, HIV-1 infection and psoriasis

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Abstract
Summary Langerhans cells (LCs) subserve an important antigen‐presenting function in the skin immune system. They bear CD4 receptors, which make them potential targets for infection with the human immunodeficiency virus (HIV‐1). The observation of reduced numbers of LCs in the skin of patients with the acquired immunodeficiency syndrome (AIDS), and the association of severe psoriasis with HIV‐1 infection, raise interesting questions regarding the role of LCs in the skin of HIV‐1‐positive psoriatic patients. In this study, LCs were quantified in the lesional and non‐lesional skin of seven HIV‐1‐positive psoriatic patients, and the results were compared with age‐, sex‐ and site‐matched HIV‐1‐negative psoriatic patients. The number of LCs was determined by staining skin sections with S‐100 polyclonal antibody, using the three‐step avidin—biotin immunoperoxidase method. The S‐100‐positive cells above the basal layer were quantified in two ways: cells/mm2 of epidermal area, and cells/mm of length of basement membrane. HIV‐1‐positive psoriatic patients showed a reduction in the number of epidermal LCs compared with HIV‐1‐negative psoriatic patients using both methods of quantification, in both lesional and non‐ lesional skin (P 2 of epidermal area (P<0·05, Wilcoxon test). This reduction was also observed when LCs were quantified per mm length of basement membrane, but the reduction was not statistically significant in the control group of HIV‐1‐negative psoriatic patients. Our findings of a reduced number of LCs in the epidermis of HIV‐1 ‐positive psoriatic patients may be associated with the clinical deterioration of psoriasis in these patients.