Ultraviolet B irradiation of skin induces mast cell degranulation and release of tumour necrosis factor-alpha.

In the 'sunburn' response in skin, dermal blood vessels are activated and traffic of dendritic Langerhans' cells altered. While these changes have been attributed to the cytokine TNF-alpha, the source of this acutely released TNF has not been identified. This report demonstrates that the 'sunburn' response, both in vivo and in vitro, is accompanied by rapid degranulation of cutaneous mast cells, with consequential release of intracellular stores of TNF. Epidermal keratinocytes were only minor contributors to local TNF production. Expression of the TNF-inducible CD62E (E-selectin/ELAM-1) and CD54 adhesion molecules on cutaneous endothelium occurred 2 h following mast cell degranulation, and this event was sensitive to blockade of mast cells with disodium cromoglycate. These results indicate that TNF release in skin in the acute sunburn response can largely be attributed to mast cells.