Suppressive effect of 2-acetyl-4-tetrahydroxybutylimidazole on contact hypersensitivity in the Skh: HR hairless mouse.

The compound 2-acetyl-4-tetrahydroxybutylimidazole (THI), a component of ammonia caramel, has been shown to cause lymphopenia and to impair several immune functions in rats and mice. In this study we show that THI effectively suppresses contact hypersensitivity dose responsively in the hairless mouse, whether administered topically or orally. The suppression was shown to be prevented by topical administration of the histamine antagonist, cimetidine, and by the dipeptide, carnosine. Splenocytes from THI-treated mice failed to elicit normal contact hypersensitivity when transferred to naive mice. This suggests that THI acts by modifying splenocyte function, perhaps via a histamine-like receptor site(s).