Mechanisms of contact photosensitivity in mice. VI. Oxygen intermediates are involved in contact photosensitization but not in ordinary contact sensitization.

To investigate the possible participation of oxygen intermediates (OIs) in the contact photosensitization process, mice were treated with long-acting liposomal-superoxide dismutase (L-SOD) before photosensitization. Photosensitization to 3,3',4',5-tetrachlorosalicylanilide (TCSA) was significantly suppressed by the pretreatment of mice with L-SOD. This suppression was not mediated by suppressor cells or due to an unresponsive state produced by the use of L-SOD. Rather, the suppression appeared to be due to the failure of production of photoallergen. L-SOD treatment induced the suppression of contact photosensitivity to TCSA but not ordinary contact sensitivity to TCSA or dinitrofluorobenzene, suggesting that the production of photoallergen is more critically dependent on the presence of OIs than that of ordinary contact allergen. The results provide evidence that OIs are produced by light absorption in the presence of oxygen and react with the biologic substrate to form photoallergens.