Candida albicans water soluble fraction (CAWS), water soluble fraction of Candida albicans mainly composed of mannoprotein-beta-glucan complex, has various biological effects, such as anaphylactoid shock and coronary arteritis. These toxicological effects fit CAWS as one of PAMPs, pathogen-associated molecular patterns. Acute anaphylactoid reaction is known to be induced by lipopolysaccharide from Escherichia coli O9 (O9 LPS), which possesses the mannose homopolysaccharide as the O-antigen region. In the present study, we compared immunotoxicological and immunochemical similarity between CAWS and O9 LPS. CAWS strongly reacted with Candida serum factors, and the reactivity was found to be partially competed with O9 LPS. CAWS induced lethal toxicity was inhibited by pretreatment of mice with i.v. injection of CAWS. The lethality was found to be inhibited by i.v. injection of O9 LPS. Vice versa, O9 LPS induced acute lethal toxicity was also inhibited by pretreatment of mice with CAWS. These results suggested that CAWS, fungal PAMPs, and O9 LPS from Gram-negative bacteria share, at least in part, immunochemical and immunotoxicological activities.