Protective Effect of a Traditional Chinese Medicine, Xiao-Chai-Hu-Tang (Japanese Name:Shosaiko-To), OnPseudomonas AeruginosaInfection in Mice

Abstract
Survival of mice after intraperitoneal (ip) or intravenous (iv) infection with Pseudomonas aeruginosa was augmented in the mice that had been pretreated ip with a Chinese traditional herbal medicine, xiao-chai-hu-tang (Japanese name: shosaiko-to) 6 hours or 4 days previously. 1) The pretreatment with shosaiko-to 6 hours previously induced an accumulation of polymorphonuclear leukocytes (PN) in the peritoneal cavity, and its protective effect against ip infection was not impaired by treatment with carrageenan, a macrophage blocking agent. These results suggested that the protective effects of shosaiko-to against P. aeruginosa infection depended mainly on PMN in mice pretreated at this timing. 2) The pretreatment with shosaiko-to 4 days previously induced an accumulation of macrophages showing an augmented phagocytosis of P. aeruginosa in vitro in the presence of immune serum, and its protective effect against P. aeruginosa was impaired by treatment with carrageenan. In addition, the pretreatment with shosaiko-to accelerated the bacterial clearance from the blood. The sera obtained from mice treated with shosaiko-to 4 days previously showed a high titer of antibody specific to P. aeruginosa. When this sera was transferred to naive mice, these recipients showed an accelerated bacterial clearance and an increased survival to challenge infection with P. aeruginosa. These results suggested that protective effects of shosaiko-to against P. aeruginosa infection at this timing depended on cooperation of macrophages and antibody which produced by stimulation of shosaiko-to, a polyclonal B cell activator. Such polyclonal antibodies were also effective on protection against encapsulated Klebsiella pneumoneae to which antibody was essential in the expression of resistance. These results suggested that shosaiko-to could augument nonspecific resistance to a variety of bacteria to which antibody plays an effective role.