By affecting the synthesis of eicosanoids
Proicosanoids, eicosanoids, and leukotrienes and other eicosanoids are metabolized from polyenoic fatty acids (γ-linolenic acid, arachidonic acid, and eicosapentaenoic acid). Eicosanoids are activated by cytokines, toxoids, zymosan, oxygen free radicals, etc., and various phospholipase of cell membranes are activated, and then mobilize the unsaturated fatty acids (ARA, EPA) in the phospholipids on the membrane, in the lipoxygen. Various types of eicosanoids are produced by the oxidation of synthase (LOX) and cyclooxygenase (COX). Eicosanoids (PG-2, TX-2, LT-4 species) synthesized from omega-6 PUFAs and eicosanoid analogues (PG-3, TX-3, LT) synthesized from omega-3 PUFAs -5) does not always have the same biological properties, so a reasonable ratio of omega-3 PUFAs to omega-6 PUFAs is essential for regulating cellular immune function. If the intake of a PUFA is too much or too little, the balance is broken and the body's immune function will be abnormal. Farndale et al. (1999) fed black cockroaches with feeds containing different ratios of omega-3 PUFAs to omega-6 PUFAs and found that the ratios of LTB4 to LTB5 and TXB2 to TXB3 in black cockroaches were significantly changed. Studies on Atlantic salmon found that different ratios of omega-3 PUFAs to omega-6 PUFAs in different sources of feed have different ratios of LTB4 to LTB5 produced by macrophages. When the ratio between LTB4 and LTB5 is the largest, The phagocytic activity of macrophages is also maximized (Bell et al., 1996). Eicosanoids regulate the body's immune function by regulating lymphocyte proliferation, antibody formation, phagocytic activity of macrophages, and macrophage respiratory burst activity.
Regulate the secretion of growth hormone releasing hormone (GRH)
PUFA can affect the sensitivity of the hypothalamus-pituitary-adrenal axis and affect the secretion of GRH. Koven et al. (2003) showed that feeding oysters with arachidonic acid increased the sensitivity of the hypothalamus-pituitary-adrenal axis, leading to high levels of cortisone. The enhancement of GRH secretion may affect the proliferation of immune cells and the synthesis of humoral immune factors, thereby enhancing the immune function of aquatic animals.
Influencing the generation of intracellular signaling molecules
Studies have shown that UFA can exert immunoregulatory effects by affecting the production of intracellular signaling molecules. Diacylglycerol (DAG) is an activator of protein kinase C (PKC) and is an important intramolecular lipid messenger of IL-2 gene expression on T lymphocytes. Jolly (1997) pointed out that feeding diets containing DHA and EPA will reduce the production of DAG by murine mitogen-activated spleen cells, thereby reducing the secretion of IL-2 and inhibiting lymphocyte proliferative responses. Acyl nitroamine alcohol is another lipid second messenger within the molecule. Recent studies have shown that it can increase the expression of IL-2 gene in T lymphocytes and promote the proliferation of lymphocytes. Jolly (1997) found that dietary EPA and DHA impaired the production of COA-activated acylnitrosamines, thereby inhibiting IL-2 secretion and lymphocyte proliferation, while AA increased its production.
Effects of Polyunsaturated Fatty Acids on Animal Immunity
Animal survival rate is a comprehensive indicator of the level of disease resistance. PUFA is very effective in improving the survival rate of animals and reducing the incidence of animals.
Addition of omega-3 PUFA to feed significantly increased the challenge of rainbow trout (Edwardsi ellaictaluri) (Kiron et al., 1995) and Atlantic salmon (Aeromonas Salmonicida) inoculated with Aeromonas Salmonicida (Thompson et al., 1996). After the survival rate. Zhao Mingjiang (2007) found that the survival rate of carp inoculated with Aeromonas hydrophila was significantly increased by 80.02% when the amount of CLA added to feed increased from 0 to 1.70%.
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