Effects of dietary n-6 and n-3 fatty acids and vitamin E on the immune response of healthy geriatric dogs

Abstract

Objective - To determine the effect of dietary n-6 to n-3 fatty acid ratios and α-tocopheryl acetate concentration on immune functions and T cell subpopulations in healthy dogs. Animals - Thirty-two 7- to 10-year old female Beagles. Procedure - For 17 weeks, dogs were fed food that contained low (1.4:1) or high (40:1) ratios of n-6 to n-3 fatty acids in combination with 3 concentrations of all rac-α-tocopheryl acetate (low, 17 mg/kg of food; medium, 101 mg/kg; high, 447 mg/kg). Dogs were inoculated twice with a keyhole limpet hemocyanin suspension at 13 and 15 weeks. Results - After 12 weeks, dogs consuming low concentrations of α-tocopheryl acetate had lower percentages of CD8+ T cells, compared with dogs consuming medium or high α-tocopheryl acetate concentrations. Also, dogs consuming low α-tocopheryl acetate concentrations had higher CD4+ to CD8+ T cell ratios. On day 4 of week 15, the percentage of CD8+ T cells was highest in dogs fed medium concentrations of α-tocopheryl acetate, compared with other dogs; however, the CD4+ to CD8+ T cell ratio was higher only in dogs fed low concentrations of α-tocopheryl acetate with high concentrations of n-3 fatty acids. Dogs consuming low concentrations of n-3 fatty acids with medium concentrations of a-tocopheryl acetate had the largest delayed-type hypersensitivity (DTH) skin test response. Conclusions and Clinical Relevance - An optimum amount of dietary α-tocopheryl acetate concentration, regardless of the dietary n-6 to n-3 fatty acid ratio, stimulates the CD8+ T cell population. Effects of an optimum amount of dietary α-tocopheryl acetate concentration on the DTH response are blunted by dietary n-3 fatty acids.