PROBLEM TO BE SOLVED: To provide polysaccharides which can be applied to pharmaceutical agents and health foods, and feed additives for livestock and fish, exert sufficient immunostimulating effect, and can be produced with low cost.SOLUTION: The present invention provides a polysaccharide which is obtained as solids by mixing one or more selected from powders of the egg, larva, pupa or imago of an insect belonging to Diptera, such as Trypetidae, Muscidae, and Stratiomyidae with a solvent in which the polysaccharide is insoluble, and removing the solvent. The polysaccharide is soluble in water, shows acidity, and has a molecular weight of from about 300,000 to about 1,800,000. The polysaccharide contains at least from about 10 to about 25 mol% of rhamnose as constituent sugar. Preferably, the polysaccharide has heat tolerance and high temperature high pressure tolerance. The polysaccharide has an adjuvanticity and a Toll-like Receptor-4 mediated effect.SELECTED DRAWING: Figure 21【課題】医薬品や健康食品、畜産用や水産用の飼料添加物として応用することの可能な、十分な免疫賦活効果を示し、かつ低コストで製造可能な多糖類の提供。【解決手段】ミバエ科、イエバエ科、及びミズアブ科等の双翅目に属する昆虫の卵、幼虫、蛹、又は成虫の粉末から選択される１又は複数を、目的とする多糖類が不溶である溶媒と混合し、前記溶媒を取り除くことによって固形物として得られる、水に可溶であり、酸性を示し、分子量が約３０万～約１８０万である多糖類。構成糖として、少なくともラムノースを約１０～約２５モル％含有する多糖類。耐熱性を有し、高温高圧耐性を有することが、好ましい多糖類。免疫賦活作用を有し、Ｔｏｌｌ－ｌｉｋｅ Ｒｅｃｅｐｔｏｒ ４を介した作用を有する多糖類。【選択図】図２１
