Effect of long-term feeding of corn oil or coconut oil diets on immune response and prostaglandin E2 synthesis of squirrel and cebus monkeys

Fatty acids, the immune response, and autoimmunity: a question of n-6 essentiality and the balance between n-6 and n-3

The essentiality of n-6 polyunsaturated fatty acids (PUFA) is described in relation to a thymus/thymocyte accretion of arachidonic acid (20:4n-6, AA) in early development, and the high requirement of lymphoid and other cells of the immune system for AA and linoleic acid (1 8:2n-6, LA) for membrane phospholipids. Low n-6 PUFA intakes enhance whereas high intakes decrease certain immune functions. Evidence from in vitro and in vivo studies for a role of AA metabolites in immune cell development and functions shows that they can limit or regulate cellular immune reactions and can induce deviation toward a T helper (Th)2-like immune response. In contrast to the effects of the oxidative metabolites of AA, the longer-chain n-6 PUFA produced by gamma-linolenic acid (18:3n-6, GLA) feeding decreases the Th2 cytokine and immunoglobulin (Ig)G1 antibody response. The n-6 PUFA, GLA, dihomo-gamma-linolenic acid (20:3n-6, DHLA) and AA, and certain oxidative metabolites of AA can also induce T-regulatory cell activity, e.g., transforming growth factor (TGF)-beta-producing T cells; GLA feeding studies also demonstrate reduced proinflammatory interleukin (IL)-1 and tumor necrosis factor (TNF)-alpha production. Low intakes of long-chain n-3 fatty acids (fish oils) enhance certain immune functions, whereas high intakes are inhibitory on a wide range of functions, e.g., antigen presentation, adhesion molecule expression, Th1 and Th2 responses, proinflammatory cytokine and eicosanoid production, and they induce lymphocyte apoptosis. Vitamin E has a demonstrable critical role in long-chain n-3 PUFA interactions with immune functions, often reversing the effects of fish oil. The effect of dietary fatty acids on animal autoimmune disease models depends on both the autoimmune model and the amount and type of fatty acids fed. Diets low in fat, essential fatty acid deficient (EFAD), or high in long-chain n-3 PUFA from fish oils increase survival and reduce disease severity in spontaneous autoantibody-mediated disease, whereas high-fat LA-rich diets increase disease severity. In experimentally induced T cell-mediated autoimmune disease, EFAD diets or diets supplemented with long-chain n-3 PUFA augment disease, whereas n-6 PUFA prevent or reduce the severity. In contrast, in both T cell- and antibody-mediated autoimmune disease, the desaturated/elongated metabolites of LA are protective. PUFA of both the n-6 and n-3 families are clinically useful in human autoimmune-inflammatory disorders, but the precise mechanisms by which these fatty acids exert their clinical effects are not well understood. Finally, the view that all n-6 PUFA are proinflammatory requires revision, in part, and their essential regulatory and developmental role in the immune system warrants appreciation.

Effect of dietary fat source on antibody production and lymphocyte proliferation in chickens

The purpose of the present study was to assess the effect of fat source on the immune response of chickens. One-day-old pullets were fed corn and soybean meal-based diets containing 7% by weight one of the following fat sources: lard, corn oil, canola oil, linseed oil (LO), or fish oil (FO). After being fed experimental diets for 3 wk, humoral and cellular immune responses were assessed. Chicks were injected with SRBC and antibody titers were measured, 7 days later, by hemagglutination. Concanavalin A (Con A), pokeweed mitogen (PWM), or lipopolysaccharide (LPS)-stimulated proliferation of splenocytes was assessed by [3H]thymidine incorporation. Results demonstrated that antibody titers in FO-fed chicks were higher (P less than .005) compared with titers in chicks fed the other fat sources. The proliferative response to Con A and PWM were 30 to 50% lower (P less than .13 and P less than .05, respectively) in chicks fed the oils rich in omega-3 fatty acids, LO and FO. The response to LPS was poor. The effect of dietary fats source on lymphocyte proliferation was completely abrogated when autologous chicken serum was excluded from the culture medium. Fat source also seemed to affect growth and feed intake of the chickens. In conclusion, dietary fat source has a significant impact on the immune response of chickens.