Carotenoids and the immune response.
There is growing evidence from in vitro and in vivo laboratory animal studies that beta-carotene can protect phagocytic cells from autooxidative damage, enhance T and B lymphocyte proliferative responses, stimulate effector T cell functions, and enhance macrophage, cytotoxic T cell and natural killer cell tumoricidal capacities, as well as increase the production of certain interleukins. Many of these effects have also been seen with carotenoids lacking provitamin A activity but having the antioxidant and singlet oxygen quenching capacities of beta-carotene. The association of immunoenhancement with decreased tumor burden in animals given carotenoids suggests a potential explanation for the epidemiological data linking lower carotenoid status with higher incidences of certain cancers. Since vitamin A is a relatively poor antioxidant and cannot quench singlet oxygen, beta-carotene may have more importance as a nutrient than simply serving as a precursor of vitamin A.
Bendich
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Clinical Nutrition, Hoffmann-LaRoche Inc., Nutley, NJ 07110.
D000818:Animals; D002338:Carotenoids / Q000494:pharmacology*; D006801:Humans; D007111:Immunity, Cellular / Q000187:drug effects; D007121:Immunocompetence / Q000187:drug effects*
D002338:Carotenoids