Two Phenotypically Distinct T Cells Are Involved in Ultraviolet-Irradiated Urocanic Acid-Induced Suppression of the Efferent Delayed-Type Hypersensitivity Response to Herpes Simplex Virus, Type 1 In Vivo

When UVB-irradiated urocanic acid, the putative photo- receptor/mediator for UVB suppression, is administered to mice it induces a dose-dependent suppression of the delayed-type hypersensitivity response to herpes simplex virus, type 1 (HSV-1), of similar magnitude to that induced by UV irradiation of mice. In this study, the efferent suppression of delayed-type hypersensitivity by UV-irradiated urocanic acid is demonstrated to be due to 2 phenotypically distinct T cells, (Thy1+, L3T4-Ly2+) and (Thy1+, L3T4+, Ly2-). The suppression is specific for HSV-1. This situation parallels the generation of 2 distinct T-suppressor cells for HSV-1 by UV irradiation of mice and provides further evidence for the involvement of urocanic acid in the generation of UVB suppression