Mechanisms of contact photosensitivity in mice. V. Persistent light reaction in mice

To elucidate the mechanism(s) of persistent light reaction (PLR), i.e. persistent light reactivity to light that continues long after all exposure to the photosensitizing compound has ceased, mice were repeatedly photosensitized with 3, 3',4',5-tetrachlorosalicylanilide (TCSA) using a procedure developed by us. After 8 weeks' photosensitization, some mice reacted with black light (BL) irradiation alone without TCSA painting. This reaction peaked at 24hr after photoelicitation, comparable to the ordinary contact photosensitivity (CPS), and the reaction could be repeatedly elicited by BL exposure alone over a period of 6 months following sensitization. However, this reaction could not be transferred to naive syngenic mice via lymph node cells or spleen cells from PLR mice. From the results obtained in the present study, it seems unlikely that PLR was elicited by cells that were autophotosensitized to self carrier protein relating to photoproducts. A possible mechanism of PLR is discussed.