MECHANISMS OF CONTACT PHOTOSENSITIVITY IN MICE .2. LANGERHANS CELLS ARE REQUIRED FOR SUCCESSFUL INDUCTION OF CONTACT PHOTOSENSITIVITY TO TCSA

The role of Langerhans cells [LC] in the induction of contact photosensitivity (CPS) to tetrachlorosalicylanilide (TCSA) was investigated in mice. CPS was induced by 2 daily paintings of 50 .mu.l of 1% TCSA in acetone plus black light irradiations for 2.5 h. Both ears were challenged with 20 .mu.l of 0.1% TCSA in ethanol plus black light irradiation for 2.5 h on day 5, and ear thickness was read at 24 h. The density of LC detected as ATPase-positive cells dramatically decreased 2 days after exposure to UVB. CPS was not induced by painting the photoallergen to the skin which had been pre-irradiated with UVB. The ear swelling response returned to the normal level when the mice were sensitized 12 days after UVB exposure in accordance with the complete regeneration of ATPase-positive cells. Dose of UVB did not affect the developmentof CPS through systemic mechanism. LC apparently play an important role in the induction of CPS.