Immunomodulatory effects of some Namibian plants traditionally used for treating inflammatory diseases.

Acanthosicyos naudinianus Acanthosicyos naudininus, Gomphocarpus fruticosus, and Cryptolepis decidua are, according to the knowledge of traditional healers, used in Namibia to treat inflammatory disorders such as pain, fever and skin rashes.Since lymphocytes are essential in inflammatory responses, the immunomodulatory effects of the plant extracts on peripheral blood mononuclear cells (PBMCs) and T-lymphocytes were evaluated.Methanolic and ethyl acetate extracts of A. naudinianus, G. fruticosus, and C. decidua were analysed for their immunomodulatory potential. PBMCs were isolated from the blood of healthy donors and incubated with the plant extracts at concentrations 100, 30, 10, 3, 1 and 0.3 μg/mL. Effects on proliferation and viability of activated human lymphocytes were assessed in comparison to ciclosporine A by flow cytometry using carboxyfluorescein succinimidyl ester (CFSE) and WST1 assay. Flow cytometry by annexin V/propidium iodide (PI) staining was performed to investigate the necrotic/apoptotic effect of the plant extracts on mitogen activated human lymphocytes. In addition, analysis on the influence of plant extracts on the regulatory mechanisms of T-lymphocytes was performed using activation marker and cytokine production assays.T-lymphocyte proliferation was inhibited in a dose-dependent manner by the extracts of A. naudinianus, G. fruticosus, and C. decidua in concentrations not causing apoptosis or necrosis. This effect was mediated by inhibition of lymphocyte activation, specifically the suppression of CD25 and CD69 surface receptor expression. Moreover, the extracts suppressed effector functions, as indicated by reduced production of IFN-γ and IL-2.The data show that the extracts of A. naudinianus, G. fruticosus and C. decidua interfere with the function of immunocompetent cells, suggesting an anti-inflammatory mode-of-action, and can, therefore, be considered as a therapeutic agent for the treatment of inflammation-related diseases. However, further studies to investigate the active components responsible for these effects have to be done.