Influence of feeding unsaturated fats on growth and immune status of mice.

Dietary polyunsaturated fatty acids alter the lipid composition and immune systems of mice. To date, most studies have been of short duration and focused on a particular immunologic assay. Adult female mice were therefore fed diets rich in 18:1(n-9) (olive oil), 18:2(n-6) (safflower oil), 18:3(n-3) (linseed oil) or 20:5(n-3) and 22:6(n-3) (fish oil-safflower oil, 9:1, wt/wt), for a 5-mo period, encompassing two breeding cycles. Offspring from the second breeding cycle were then fed these diets for 42 d, and a spectrum of immune functions was assessed. Dietary fat had a small effect on gestational weight gain and total and relative organ weights of the offspring. The relative amounts of splenic Ly-2 and gamma delta receptor-expressing T cells were proportional to the concentration of 18:2(n-6), and inversely proportional to the concentration of long chain (n-3) polyenes in the diet. In contrast, Ly-1, immunoglobulin M, GM1+, and Ly-1 B suppressor inducer cells were not significantly affected by dietary fat. Splenic natural killer cell and lymphokine activated killer cell activities were attenuated by (n-3) polyunsaturated fatty acids, in contrast to superoxide production of stimulated macrophages which was increased. Those immune functions that were sensitive to dietary fat modulation will be the focus of continued research.