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 α-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. (Am J Vet Res 2003;64:762–772)