EFFECT OF UV EXPOSURE AND BETA-CAROTENE SUPPLEMENTATION ON DELAYED-TYPE HYPERSENSITIVITY RESPONSE IN HEALTHY OLDER MEN

Objectives: The aims of this study were to determine if ultraviolet li ght (UV) is immunosuppressive in healthy older males, if beta-carotene (beta C) supplementation could prevent any observed UV-induced immuno suppression, and to compare these effects with those observed previous ly in younger men. Methods: The study was a placebo-controlled, random ized trial that employed a 2x2 factorial design. Healthy older men (me an age 65.5 years) received 30 mg beta C or placebo daily throughout t he 47-day trial, while on a low carotenoid diet. After 28 days, half o f each group received 12 suberythemic exposures to UV over a 16-day pe riod. Delayed-type hypersensitivity (DTH) tests and plasma carotenoid assays were performed at baseline, pre-UV and post-UV time points, wit h DTH testing performed on an area of skin protected from UV exposure. Results: UV exposure resulted in significantly suppressed DTH respons e in the placebo group but not in the beta C-UV group. While there was no significant interaction between beta C supplementation and UV on D TH response, there was a significant inverse relationship between fina l plasma beta C concentration and extent of UV-induced suppression of DTH response. A similar correlation existed among subjects not exposed to UV. Conclusions: Suberythemic UV exposure was immunosuppressive, a s measured by DTH response, in healthy older men as in younger men. Hi gher plasma beta C was significantly associated with maintenance of DT H response, although the extent of protective effect of beta C appeare d less than previously observed in younger subjects. The attenuated ef fect of beta C in the older UV-exposed subjects may have resulted in p art from muted plasma PC responses to beta C supplementation and/or hi gher plasma vitamin E levels than those of younger men. The finding th at stronger DTH responses were associated with higher plasma beta C co ncentrations in both UV and non-UV subjects further supports a role fo r this nutrient in immunomodulation.