ISSUE FOCUS FEED & ADDITIVE MAGAZINE September 2022 31 posed of D-glucose units with β-1, 3 connections. While β-1, 3 glucan is obtained from Schizophyllum commune, yeast glucan (1-3 and 1-6 linked glucan) is recovered from Saccharomyces cerevisiae cell walls. The β-glucans found in cereals (wheat, rye, barley) have both 1,3 and 1,4 backbone linkages. Some types of seaweed and several species of mushrooms, such Shiitake and Maitake, are additional sources. Additionally, bacteria (curdlan from Alcaligenes faecalis) create β-glucans, which is found in grains (Harada et al., 1968). AN IMMUNOSTIMULANT IS WHAT? A substance that directly interacts with system cells to excite them is known as an immunostimulant. It might be a substance, medication, or stressor (Barman et al., 2013). They activate the key immune system components, such as phagocytosis, the properdin and complement systems, protective secretory IgA antibodies, the release of α and γ-interferon, T- and B-lymphocytes and the production of certain antibodies and cytokines. Immunostimulants boost the host's natural immunity, enhancing its ability to fight off infections. Immunostimulants' ability to enhance phagocytic cell activity and increase their fungicidal and bactericidal capabilities is their most well-documented impact. Beta glucan is strongly stimulatory to macrophages (Seljelid et al., 1984). White blood cells known as macrophages are an essential component of the immune system that protects multicellular organisms against infections. WHY IMMUNOSTIMULANTS ARE PREFERRED OVER VACCINES? Immunostimulants are nonspecific, because they can increase immunity to a wide variety of diseases, whereas vaccinations provide resistance to only one or two particular pathogens and temporarily shield the body from sickness. Compared to vaccinations, which are more expensive and have a narrower spectrum of action, immunostimulants are less expensive and more effective. In case of fish and shrimp larvae, immunostimulants are much easier to administer than vaccines. β- GLUCANS AS MODIFIERS OF BIOLOGICAL RESPONSE (BRM) Biological response modifiers are a class of chemical substances with physiological activity. β-glucans are a part of BRMs, which are known for their striking physiological effect. BRM may be categorized into: i) Cytokines: which are in charge of regulating the immune system and facilitating communication between the cells of immune system. ii) Immuno-modulators: These substances can either stimulate or depress the immune system (Immuno-suppressants). General Structure of β-Glucan
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