Modulation of the chicken immune cell function by dietary polyunsaturated fatty acids

Polyunsaturated fatty acids (PUFA) possess a wide range of biological properties, including immunomodulation. The amount, type, and ratio of dietary PUFA determine the types of fatty acids that are incorporated into immune cell membranes. Consequently, the physiological properties of immune cells and their potential to produce communication molecules, such as eicosanoids, can be modulated. This thesis aims to describe the (interaction) effects of n-3 and n-6 PUFA after challenge with antigens of various nature, and thereby to identify PUFA requirements for optimal immune responses in chickens. Antibody responses to model antigens known to induce T helper-1 and T helper-2 type responses in mice were increased or decreased by n-6, and increased or not affected by n-3 PUFA, depending on the antigen, and levels of other PUFA. Cutaneous hypersensitivity, an index for in vivo T cell reactivity, was increased by n-3 and decreased by n-6 PUFA or not affected. In vitro T cell reactivity was increased in chickens fed n-3 PUFA enriched diet. Evidence that vitamin E interacts with PUFA effects on immune cell function, particularly at high PUFA levels, was not found. Cytokine mRNA levels early after LPS challenge were increased by long-chain n-3 PUFA or not affected by dietary PUFA. The present thesis indicates that dietary PUFA have the potential to modulate chicken immune cell function, but that most effects are the contrary of what is usually found in mammals. The differences are possibly due to differences in chickens and mammals with regard to the metabolism and effector functions of PGE ₂ , and the effects of dietary n-3 on cytokine production. It is hypothesized that inclusion of 1-2 % of n-3 and inclusion of no more than 3-4 % of n-6 in the diet, is optimal for Ab responsiveness, enhances T cell reactivity, and possibly improves chicken's disease