Abstract:The chemical structure of fungal polysaccharide AbEXP 1-a was studied through acid hydrolysis, IR spectroscopy and NMR spectroscopy. And its immunomodulating activity was tested through animal experiments. The results are as follow: AbEXP 1-a is consisted of glucose and mannose in ratio of 3:1. Its backbone was deduced that consisted of 3 glucoses combined by β-(1→6) glycosidic linkage and a meanose linking to them through α-(1→6) or β-(1→6) glycosidic linkage. AbEXP 1-a was found to be capable of promoting non-specific immunity, humoral immunity and cellular immunity of mice. Besides, it also could promote delayed type hypersensitivity in mice. All that means that AbEXP 1a could enhance the immunity of organisms comprehensively and the appropriate dosage is 10 mg/kg body weight.