1. Promote the development of immune organs

The immune system of animal body consists of immune organs, immune cells and immune factors. As the main place for lymphocyte and other immune cells to proliferate, differentiate, mature and produce immune response, the development, maturity and physiological status of immune organs have a great impact on the immune function of the body. As a kind of yeast feed material, yeast cell wall polysaccharide can promote the development and maturation of immune organs of various young animals. When 1% yeast polysaccharide suspension was added to the drinking water, the weight of thymus, spleen and bursa of Fabricius increased significantly, and the volume of tonsil in cecum increased significantly. The weight of spleen, thymus and bursa of Fabricius in broilers increased significantly when the polysaccharide of stem yeast cell wall was added to the feed, and the effect was good when the dosage was 0.2%. It has also been reported that yeast cell wall polysaccharides can significantly improve the spleen, thymus and serum hemolysin of immunocompromised mice.

2. Enhance immunity

It has been shown that yeast cell wall polysaccharide can enhance the non-specific and specific immune response of animal body. Through the cooperation of non-specific and specific immune system, animal body can resist pathogen invasion, pathogen identification and pathogen clearance. At the same time, yeast cell wall polysaccharides can promote the development of immune organs, induce the maturation of immune function, promote the formation of macrophages and plasma cells, and enhance the ability of resistance to disease and stress. It was found that adding 0.25%, 0.50% and 0.75% mannan to feed could significantly improve the activities of gastrointestinal protease, serum superoxide dismutase and alkaline phosphatase, and enhance the immunity of tilapia. It was found that the content of IL-2 and IFN - γ could be significantly increased by adding yeast polysaccharide to the diet. Similarly, the content of IL-2 and IFN - γ increased significantly when yeast polysaccharide was added to the diet of breeders. It was found that the lysozyme content in serum and the proportion of T-lymphocyte were significantly increased by adding yeast cell wall polysaccharide to the diet. It was found that yeast mannan could significantly improve the lymphocyte transformation rate and phagocytic capacity of weaned piglets. It was found that yeast cell wall polysaccharide could promote the expression of TLR-2, tnf-6 and proinflammatory factor IL-1 β gene, so as to inhibit the occurrence of excessive inflammation and relieve the stress of piglets. It can be seen from the above that the polysaccharide of yeast cell wall can enhance the immunity of many kinds of animals.

3. Restoring the immune function of immunosuppressed animals

Yeast cell wall polysaccharides and enzymes can not only enhance the immunity of healthy animals, but also restore the immune function of immunosuppressed animals. It was found that yeast cell wall polysaccharide could significantly improve the lymphocyte proliferation, phagocytosis rate of macrophages, NK cell activity and the content of IL-4 and IFN - γ in serum of immunosuppressed mice.