Dose response studies for UVA in contact photosensitivity to TCSA in the mouse

We performed UVA dose response studies for contact photosensitivity (CPS) to 3,3',4',5-tetrachlorosalicylanilide (TCSA) in BALB/cJ mice using the back for induction and the ears for elicitation. The dose of TCSA was kept constant. The challenge procedure in non-sensitized mice produced a phototoxic response at 24 h after challenge. None of the 11 mice tested showed simple contact sensitivity (CS) to TCSA. Vigorous CPS responses were achieved with sensitization doses of UVA as low as 0.5 J/cm2 and the peak reaction occurred at 24 h after challenge. UVA sensitization doses less than 0.5 J/cm2 gave responses that were reduced in a dose-related manner and the peak response was delayed to 48 h or longer after challenge. The maximum elicitation dose of 6.0 J/cm2 UVA gave the greatest response and almost all ears showed vigorous reactions if the sensitization dose was 0.5 J/cm2 or greater. Lower elicitation doses gave lesser reactions in a dose-related manner. Cyclophosphamide (Cy) pretreatment increased the CPS reaction by about 50%.