Ultraviolet A irradiation of the eye induces immunomodulation of skin and intestine in mice via hypothalomo-pituitary-adrenal pathways.

Irradiation by ultraviolet A (UVA) initiates the suppression of skin contact hypersensitivity. However, the change in the whole body immunity by UVA irradiation of the eye is still unknown. The mice used in this study were separated into four groups namely: a control, UVA irradiation of the eye, UVA irradiation of the ear, UVA irradiation of the eye + a glucocorticoid receptor antagonist (RU-486) administrated, UVA irradiation of the eye with an adrenalectomy and non-irradiation + cortisol administrated groups. The eye or ear was locally exposed to UVA after covering the remaining body surface with aluminum foil at a dose of 110 kJ/m(2) using a FL20SBLB-A lamp. Plasma adrenocorticotropic hormone, cortisol, and interleukin-10 (IL-10) content increased by UVA irradiation of the eye. In addition, UVA irradiation of the eye induced down-regulation of the epidermal Langerhans cells in the ear and the up-regulation of the mucosal immunoglobulin A (IgA) in the intestine. However, the changes in the epidermal Langerhans cells and mucosal IgA of UVA irradiation of the eye are not induced either by the RU-486 treatment or an adrenalectomy. These results clearly indicate that the signal evoked by UVA irradiation of the eye, through the hypothalamo-pituitary-adrenal pathway, up-regulated the production of glucocorticosterone. This hormone controls immunity, and the possibility that it performed a living body defense for UVA exposure was thus suggested.