IL1/ETAF activity and undetectable IL1 beta mRNA and minimal IL1 alpha mRNA levels in normal adult heat-separated epidermis.

Interleukin 1 (IL 1), a cytokine expressed from a number of cell types, plays a vital part in immune and inflammatory processes. Epidermal IL1-like activity, also known as epidermal cell thymocyte-activating factor (ETAF), is associated with whole skin, epidermis, Langerhans cells and cultured keratinocytes and keratinocyte cell lines. We show that preparations of heat-separated epidermis possess abundant IL1/ETAF activity as indicated by PGE/collagenase induction in cultured synovial cells and proliferation of mouse thymocytes. However, using cDNA probes to interleukin-1 alpha and beta we show that freshly isolated heat-separated epidermis from healthy adult donors contains only a slight detectable level of IL1 alpha mRNA by dot blot analysis and no IL1 beta and IL1 alpha mRNA by Northern blot analysis. The implications of these observations will be discussed.