Immunomostimulatory Activity of Aqueous Extract of Azadirachta indica Flowers on Specific and Non Specific Immune Response

Neem (Azadirachta indica A. Juss) is one of the most useful traditional medicinal plants in India. Neem flowers are traditionally used as tonic and stomachic. Neem leaf, stem and seed oil has proved immunomodulatory activity along with the adverse effect on sperm count. Therefore, the aim of the present study was to evaluate immunomodulatory activity of aqueous extract of Azadirachta indica flowers on humoral and cell mediated immune response to ovalbumin, phagocytic activity by carbon clearance test and cyclophosphamide induced myelosuppression. The extract was also examined for the ability to induce secretory and cellular responses in murine peritoneal macrophages in vitro. The extract increased the production of super oxide (O₂-) and nitric oxide (NO) in murine peritoneal macrophages. These results indicate that reactive oxygen intermediates (ROI), reactive nitrogen intermediates (RNI) are likely major mediators of cytotoxic activity of extract treated macrophages. The extract showed significant increase in phagocytic index which indicates activation of reticuloendothelial system through release of the mediators. The extract also showed increase in antibody titer against the ovalbumin and protection towards the cyclophosphamide induced myelosuppression in dose dependent manner. Increase in cell mediated immunity by increasing paw edema against ovalbumin showed significant effect of the extract on stimulation of T cell at the dose 400 mg/kg. Present study, therefore, reveals that the extract holds promise as immunomodulatory agent, which acts by stimulating both specific (humoral and cell mediated immunity) and non specific immune response (cytotoxic and phagocytic activity of macrophages).