Immunological Investigations, 39:245–267, 2010 Copyright © Informa Healthcare USA, Inc. ISSN: 0882-0139 print / 1532-4311 online DOI: 10.3109/08820131003599585 LIMM 0882-0139 1532-4311 Immunological Investigations, Vol. 39, No. 3, February 2010: pp. 0–0 Immunological Investigations The Effects of Phyllanthus niruri Aqueous Extract on the Activation of Murine Lymphocytes and Bone Marrow-Derived Macrophages Immunostimulation by P. niruri Aqueous Extract C. S. Nworu et al. C. S. Nworu, 1,5 P. A. Akah, 1 F. B. C. Okoye, 2 P. Proksch, 3 and C. O. Esimone 4 1 Department of Pharmacology & Toxicology, Faculty of Pharmaceutical Sciences, University of Nigeria, Nsukka, Nigeria 2 Department of Pharmaceutical & Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Nigeria, Nsukka, Nigeria 3 Institute of Pharmaceutical Biology and Biotechnology, Heinrich-Heine University, Düsseldorf, Germany 4 Department Pharmaceutical Microbiology & Biotechnology, Faculty of Pharmaceutical Sciences, Nnamdi Azikiwe University, Awka, Nigeria 5 Department of Molecular & Medical Virology, Ruhr-University, Bochum, Germany Phyllanthus niruri L. (Euphorbiaceae) is acclaimed world-wide for its versatile ethno- medicinal uses. It features in recipes used by some herbalists to manage different diseases, including claims of efficacy against many life-threatening infections, such as HIV/AIDS and hepatitis. In order to understand the mechanisms and the involvement of the immune system in mediating these activities, the effects of the aqueous extract of P. niruri on the activation of murine lymphocytes and macrophages were investi- gated. The study showed that the extract of P. niruri is a potent murine lymphocytes mitogen, inducing significant (p < 0.01) increases in the expression of surface activa- tion maker (CD69) and proliferation of B and T lymphocytes. The production of inter- feron-g (IFN- g) and interleukine-4 (IL-4) by P. niruri extract-stimulated naïve splenocytes cultures was also significantly (p < 0.05) increased in a concentration- dependent manner. Various indices of activation and functions murine bone marrow- derived macrophages were significantly (p < 0.05) enhanced by pre-treatment with the extract, including phagocytosis, lysosomal enzymes activity, and TNF-a release. Phyllanthus niruri extract was also shown to modulate nitric oxide release by macroph- ages. These activities suggest that stimulation of the immune system by the extracts of Address correspondence to C. S. Nworu, Department of Pharmacology & Toxicology, Faculty of Pharmaceutical Sciences, University of Nigeria, Nsukka, Nigeria; E-mail: csnworu@yahoo.com