A GARLIC EXTRACT PROTECTS FROM ULTRAVIOLET-B (280-320 NM) RADIATION-INDUCED SUPPRESSION OF CONTACT HYPERSENSITIVITY

Lyophilized aged garlic extract has been incorporated at concentration s of 0.1%, 1% and 4% by weight into semipurified powdered diets and fe d to hairless mice. Under moderate UVB exposure conditions resulting i n 58% suppression of the systemic contact hypersensitivity response in control-fed mice, a dose-responsive protection was observed in the ga rlic-fed mice; contact hypersensitivity in the UVB-exposed mice fed 4% garlic extract was suppressed by only 19%. If the UVB exposure was re placed by topical application of one of a series of lotions containing increasing concentrations of cis-urocanic acid, a dose-responsive sup pression of contact hypersensitivity was demonstrated in control-fed m ice (urocanic acid at 25, 50, 100 and 200 mu g per mouse resulting in 22-46% suppression). Mice fed a diet containing 1% aged garlic extract were partially protected from cis-urocanic acid-induced suppression o f contact hypersensitivity, with greater protection from the lower con centrations of urocanic acid. Mice fed a diet containing 4% aged garli c extract were protected from all concentrations of urocanic acid. The results indicate that aged garlic extract contains ingredient(s) that protect from UVB-induced suppression of contact hypersensitivity and suggest that the mechanism of protection is by antagonism of the cis-u rocanic acid mediation of this form of immunosuppression.