Imoviral is a natural product formulation containing a mixture of uncaria, shiitake and ribes extracts. All ingredients are recognized as antioxidant, anti-inflammatory agent and immunomodulant. In order to evaluate the rational basis of extract mixture as immunomodulatory agent, we tested the effect of Imoviral formulation on macrophage response to lipopolysaccharide (LPS)-induced stress. The effect was evaluated as variation of reactive oxygen species (ROS) and prostaglandin E2 (PGE2) production and as cytokine gene expression. The extract did not affect cell viability up to 250 μg/ml. Treatment with extract (10-150 μg/ml) reduced ROS and PGE2 production as well as IL-8 and TNF-α gene expression. A pre-treatment with extract blunted LPS-induced production of ROS and PGE2, markers of oxidative and inflammatory stress, as well as the gene expression of all cytokines tested, indicators, in vitro, of immune response activation. In conclusion, we demonstrated that Imoviral formulation could be a useful tool to modulate the immune function, reducing the oxidative and inflammatory markers related to bacterial attack. Experimental data suggest that Imoviral extract mixture could also represent a preventive pharmacological strategy to enhance cell resistance to bacterial infections.