Production of LTB4-like chemotactic arachidonate metabolites from human keratinocytes

Keratinocytes have recently been recognized as a source of mediators of cellular immune function. We present here further data on the production of 5-lipoxygenase-dependent arachidonate metabolites from freshly isolated human epidermal cells. Stimulation of cells with arachidonic acid or the calcium ionophore A 23187 alone or together caused a dose- and time-dependent release of chemotactic activity which was maximal during the first 10 min and which continued for up to 18 h. Indomethacin (10(-6) M) enhanced and compound BW 755C (20 micrograms/ml), a lipoxygenase inhibitor, decreased release. The chemotactic activity was heat stable for 30 min at 56 degrees C and was extractable into ether at pH 3.0. Analysis of 15- and 30-min supernatants showed coelution of biologic activity and of leukotriene B4 (LTB4), as measured by radioimmunoassay, at marker positions of LTB4 and of 20-OH-LTB4. Elimination of Langerhans cells did not alter the secretion of chemotactic lipids, suggesting that keratinocytes are the main source of potent, biologically active, lipoxygenase-dependent arachidonate metabolites.