Tumour necrosis factor-α induces Langerhans cell migration in humans

The role of tumour necrosis factor (TNF)-alpha in the mobilization and migration of human epidermal Langerhans cells (LC) has been investigated. Intradermal injection of normal human volunteers with homologous recombinant TNF-alpha was found to cause a dose-dependent reduction in the frequency of LC within epidermal sheets 2 h later. Equivalent results were obtained when epidermal LC were identified on the basis of either CD1a or HLA-DR expression. At the dose of TNF-alpha used routinely (500 U), treatment resulted in an average reduction in LC density of approximately 24%. Treatment with TNF-alpha was associated with a perivascular polymorphonuclear infiltration at 2 h, but the epidermis appeared normal with neither fibrinoid necrosis nor vasculitis, and LC morphology was not affected significantly. These results demonstrate that TNF-alpha provides an important signal for LC migration in humans and is likely therefore to play a crucial part in the induction of cutaneous immune responses.