Migration of Langerhans cells and gamma delta(+) dendritic cells from UV-B-irradiated sheep skin

Depletion of dendritic cells from UV-B-irradiated sheep skin was investigat ed by monitoring migration of these cells towards regional lymph nodes. By creating and cannulating pseudoafferent lymphatic Vessels draining a define d region of skin, migrating cells were collected and enumerated throughout the response to UVB irradiation. In the present study, the effects of expos ing sheep flank skin to UV-B radiation clearly demonstrated a dose-dependen t increase in the migration of Langerhans cells (LC) from the UV-B-exposed area to the draining lymph node. The range of UV-B doses assessed in this s tudy included 2.7 kJ/m(2), a suberythemal dose; 8 kJ/m2, 1 minimal erythema l dose (MED); 20.1 kJ/m(2); 40.2 kJ/m(2); and 80.4 kJ/m(2), 10 MED. The LC were the cells most sensitive to UV-B treatment, with exposure to 8 kJ/m(2) or greater reproducibly causing a significant increase in migration. Migra tion of gamma delta (+) dendritic cells (gamma delta (-) DC) from irradiate d skin was also triggered by exposure to UV-B radiation, but dose dependenc y was not evident within the range of UV-B doses examined. This, in conjunc tion with the lack of any consistent correlation between either the timing or magnitude of migration peaks of these two cell types, suggests that diff erent mechanisms govern the egress of LC and gamma delta (+) DC from the sk in. It is concluded that the depression of normal immune function in the sk in after exposure to erythemal doses of UV-B radiation is associated with c hanges in the migration patterns of epidermal dendritic cells to local lymp h nodes.