Background: Plant extracts have been widely investigated for possible immunomodu-latory properties.
Objective: To study the immunomodulatory functions of the metha-nol extract of Haussknechtia elymatica (Apioideae), an herb native to south-western Iran.
Methods: Delayed type hypersensitivity (DTH) skin test and measurement of an-tibody titer after immunization with Sheep-RBC was performed. [3H]-thymidine incor-poration assay on the human lymphocytes stimulated with PHA and determination of IL-2 production using ELISA method was carried out.
Results: Treatment of mice with increasing concentrations of the extract decreased the footpad thickness indicating a dose-related inhibitory effect of H. elymatica on delayed hypersensitivity. The mean antibody titers for all concentrations of the extract at primary and secondary responses were significantly less than the control. Addition of the extract to the culture of human peripheral blood lymphocytes in the presence of mitogen decreased cell proliferation dose-dependently. A dose related decrease in production of IL-2 in extract-treated cells was also observed.
Conclusion: The decline of antibody titer and DTH response indi-cates that H. elymatica, by acting on the lymphocyte proliferation and IL-2 secretion, inhibits both humoral and cell-mediated immune responses.