Dietary β-Carotene Stimulates Cell-Mediated and Humoral Immune Response in Dogs

The role of β-carotene on immune response in domestic dogs is not known. Female Beagle dogs were fed 0, 2, 20 or 50 mg β-carotene/d; blood was sampled at wk 0, 1, 2, 4 and 8 for analysis of the following: lymphoproliferation, leukocyte subpopulations and concentrations of interleukin-2 (IL-2), immunoglobulin (Ig)G and IgM. Delayed-type hypersensitivity (DTH) response was assessed at wk 0, 3 and 7. β-Carotene supplementation increased plasma β-carotene concentrations in a dose-dependent manner. Compared with unsupplemented dogs, those fed 20 or 50 mg of β-carotene had higher CD4+ cell numbers and CD4:CD8 ratio. However, there was no treatment difference in CD8+, CD21+ and major histocompatability complex (MHC) class II+ cells. Plasma IgG, but not IgM concentration was higher in dogs fed β-carotene throughout the study period. The DTH response to phytohemagglutinin (PHA) and vaccine was heightened in β-carotene–supplemented dogs. β-Carotene feeding did not influence mitogen-induced lymphocyte proliferation or IL-2 production. Immune response was impaired in dogs classified as low β-carotene absorbers compared with similar dogs fed the same amount of β-carotene. Therefore, dietary β-carotene heightened cell-mediated and humoral immune responses in dogs.