Immunological In Vivo and In Vitro Investigations of Aqueous Extract of Stem Bark of Pterocarpus erinaceus Poir (Fabaceae).

BACKGROUND: Macrophages are the first cells to recognize invading foreign bodies and are central to cell mediated and humoral immunity. Therefore, the activation of macrophages is a key event for effective innate and adaptive immunity. Pterocarpus erinaceus has been reported to control infectious diseases, but the mechanism remains to be elucidated. In this study, we demonstrated the immune-modulatory effect of aqueous extract of P. erinaceus using human macrophages and lymphocytes, as well as mice. METHODS: Hot water was used to extract P. erinaceus from the stem bark. Its effect on lymphocytes was measured by evaluating proliferative response and delayed hypersensitivity. Phagocytic activity of macrophages were measured based on neutral red uptake assay, nitric oxide production and myeloperoxidase and phosphatase acid activity. Hematopoietic and infectious activities were analyzed using the effect on infectious stress and chloramphenicol-induced leucopenic mice model. RESULTS: Aqueous extract showed stronger stimulatory effects on the neutral red uptake, production of nitric oxide and phosphatase acid activity in lipopolysaccharide-activated macrophages. In addition, aqueous extract significantly stimulated the proliferation of phytohemagglutinin-activated lymphocytes, enhanced delayed hypersensitivity response to erythrocytes and attenuated infection-induced fever. Furthermore, aqueous extract also significantly increased the rate of recovery of white blood cell levels in chloramphenicol-induced leucopenia mice. CONCLUSIONS: The results suggest that aqueous extract of P. erinaceus stem bark is able to modulate the immune system and has potential effects in clinical conditions when an immune-enhancing and anti-infectious effect is desired.