In situ localization of lnterleukin-6 in normal skin and atrophic cutaneous disease

Interleukin-6 (IL-6) is a multifunctional cytokine that participates in the inflammatory and immune responses. In human skin, keratinocytes produces IL-6, although the in vivo role of this cytokine is unknown. In the present study we investigated the in situ localization of IL-6 in normal epidermis (n = 10) and in a group of skin diseases characterized by epidermal atrophy. Formalin-fixed paraffin-embedded skin biopsies from patients with clinical and histopatholog- ical features consistent with localized scleroderma (n = 10), systemic scleroderma (n = 5), lichen sclerosus et atrophicus (n = 9) and balanitis xerotica obliterans (n = 7) were tested using polyclonal antibodies and avidin-biotin- peroxidase immunostaining. We demonstrated the presence of IL-6 in normal epidermis and in atrophic skin diseases. In normal skin there was moderate intercellular and intracellular reactivity detected using a high antibody concentration. In specimens with epidermal atrophy we detected intense cytoplasmic and intercellular immunostaining using a lower antibody concentration. The immunoreactivity was independent of the epidermal thickness. Plasma IL-ö, measured by radioimmunoassay, was not elevated in plasma from patients with localized or systemic scleroderma. Increased IL-6 in the epidermis of selected skin diseases suggests that IL-6 may be related to the pathophysiology of der- matologic diseases characterized by epidermal atrophy.