By affecting the synthesis of eicosanoids

Eicosanoids such as prostaglandins, thromboxanes and leukotrienes are metabolized by polyene fatty acids (γ-linolenic acid, arachidonic acid and eicosapentaenoic acid). Eicosanoids are stimulated by cytokines, toxoids, zymosins, oxygen free radicals, etc., and various phospholipases are activated by cell membranes, and then mobilize unsaturated fatty acids (ARA, EPA) in phospholipids on the membrane, in lipox Various types of eicosanoids are produced by the oxidation of synthase (LOX) and epoxidase (COX). Eicosanoids (PG-2, TX-2, LT-4) synthesized by omega-6 PUFA and eicosanoid analogues synthesized by omega-3 PUFA (PG-3, TX-3, LT) -5) does not always have the same biological properties, so a reasonable ratio of omega-3 PUFA to omega-6 PUFA is critical for regulating cellular immune function. If the intake of a certain PUFA is too much or too little, this balance is broken and the body's immune function will be abnormal. Farndale et al. (1999) fed black carp with feeds containing different ratios of omega-3 PUFA to omega-6 PUFA, and found a significant change in the ratio of LTB4 to LTB5 and TXB2 to TXB3 in black sputum plasma. Studies on Atlantic salmon have found that the ratio of LTB4 to LTB5 produced by macrophages is also significantly different for different sources in feed due to their different ratios of omega-3 PUFA to omega-6 PU?FA, when the ratio of LTB4 to LTB5 is the largest. The phagocytic activity of macrophages is also maximal (Bell et al., 1996). Eicosanoids regulate the immune function of the body by regulating lymphocyte proliferation, antibody formation, phagocytic activity of macrophages, and respiratory burst activity of macrophages.

Regulates the secretion of growth hormone releasing hormone (GRH)

PUFA can affect the sensitivity of the hypothalamic-pituitary-adrenal axis and affect the secretion of GRH. Koven et al. (2003) showed that feeding sea urchins with arachidonic acid-rich feed increased the sensitivity of the hypothalamic-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 proteins such as humoral immune factors, thereby enhancing the immune function of aquatic animals.

Affect intracellular signal molecule generation

Studies have shown that UFA can exert immunomodulatory effects by affecting the production of intracellular signaling molecules. Diacylglycerol (DAG) is an activator of protein kinase C (PKC) and is an intramolecularly important lipid second messenger for IL-2 gene expression on T lymphocytes. Jolly (1997) pointed out that feeding a diet containing DHA and EPA would reduce the production of DAG by murine mitogen-activated splenocytes, thereby reducing IL-2 secretion and inhibiting lymphocyte proliferation. The acyl nitramine is another lipid second messenger in the molecule. Recent studies have shown that it can enhance IL-2 gene expression in T lymphocytes and promote lymphocyte proliferation. Jolly (1997) found that dietary EPA and DHA impaired the production of COA-activated acyl nitramine, thereby inhibiting IL-2 secretion and lymphocyte proliferation, while AA increased its yield.

Effect of polyunsaturated fatty acids on animal immunity

The survival rate of animals is a comprehensive indicator of the level of disease resistance. PUFA works very well in improving animal survival and reducing animal morbidity.

The addition of omega-3 PUFA to the feed significantly increased the attack of Edwards (Edwardsi?ellaictaluri) rainbow trout (Kiron et al., 1995) and Aeromonas Salm monicida (Thompson et al., 1996). Survival rate after poisoning. Zhao Mingjiang (2007) on the study of carp found that when the amount of CLA in feed increased from 0 to 1.70%, the survival rate of squid inoculated with Aeromonas hydrophila was significantly increased by 80.02% (P<0.01), further improved. There was no significant change in the survival rate of CLA addition. Omega-3 PUFA can also increase the survival rate of guinea pigs (Barton et al., 1991) and rats (Mascioli et al., 1988) after injection of bacterial lipopolysaccharide (LPS), and increase Staphylococcus aureus (Rayon et al., 1989), Streptococcus ssp (Sadeghi, etc.). , 1999) and retrovirus (murineret? rovirus) (Xi et al, 1998) survival rate after challenge. The results of the experiment conducted by the Anhui Agricultural University Animal and Poultry Disease Prevention Research Institute showed that the addition of perilla seed extract to the diet reduced the mortality rate of Avian broiler by 41.23%. The results of experiments conducted by Chongqing Mingyang Breeding Co., Ltd. showed that the perilla seed extract can replace the antibacterial feed additive used in pig diet and reduce the incidence.