Modulation of melanocyte intercellular adhesion molecule-1 by immune cytokines

Human melanocyte expression of intercellular adhesion molecule-1 (ICAM-1) with or without stimulation by interferon gamma (IFN-G), tumor necrosis factor alpha (TNF-alpha), or interleukin-1-alpha (IL-1 alpha), was measured utilizing direct immunofluorescence and fluorescence-activated cell sorting (FACS). Melanocytes grown in vitro expressed low levels of ICAM-1, which could be increased by exposing the cells to IFN-G, TNF-alpha, or IL-1 alpha. Each cytokine caused an enhancement of melanocyte ICAM-1 expression in a dose-dependent fashion. The lowest dose necessary to cause a significant increase in melanocyte ICAM-1 expression was 1 U/ml IFN-G, 0.3 ng/ml TNF-alpha, or 3 U/ml IL-1 alpha. Melanocytes were most sensitive to TNF-alpha stimulation, with the greatest levels of ICAM-1 expression following 30 ng/ml or more TNF-alpha. When IFN-G was added to melanocyte cultures in combination with TNF-alpha or IL-1 alpha, there was an additive increase in ICAM-1 expression but no synergy was noted with the combined cytokines. To our knowledge, this is the first report of melanocyte ICAM-1 induction by TNF-alpha and IL-1 alpha and by physiologically relevant doses of IFN-G. Because of the importance of ICAM-1 in the regulation of immune cell-target interactions, the study of ICAM-1 expression by melanocytes may help us to better understand immune mechanisms of melanocyte injury.