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Human epidermal cell thymocyte-activating factor (ETAF) derived from either normal epidermal cells or a squamous cell carcinoma cell line has recently been shown to be a low m.w. protein that is indistinguishable from human macrophage-derived interleukin 1 (IL 1). As with human IL 1, human ETAF elutes from Sephadex S-200 gel in two major peaks at m.w. 70,000 to 40,000 and m.w. 25,000 to 12,000. Rechromatography of the higher m.w. fraction of ETAF yielded some of the lower m.w. activity, and chromatofocusing of high m.w. ETAF yielded the same three isoelectric points as the lower m.w. ETAF. Partially purified human ETAF as well as IL 1 were chemotactic for polymorphonuclear and mononuclear leukocytes. In addition, exposure of PMN to ETAF stimulated increased metabolic activity as demonstrated by greater reduction of intracellular nitroblue tetrazolium. Therefore, this study lends further support for an important role of ETAF in the pathogenesis of inflammatory skin diseases.
Luger et al. (Mon,) studied this question.