We have studied natural killer (NK) activity, lymphoproliferative response, the release of several cytokines (IL-2, TNFa and IL-1b) and the ROS production in peritoneal leukocytes obtained 0, 2, 4, 12 and 24 h after lipopolysaccharide (LPS) injection. Lethal septic shock (100 % mortality occurred at 30 h after LPS administration) was caused in female BALB/c mice by intraperitoneal injection of 100 mg/kg of E. coli LPS. Cytotoxicity and lymphoproliferation assay were preformed together with the measurement of IL-1b, IL-2 and TNFa production, and quantification of ROS. Natural killer activity, spontaneous lymphoproliferative response, IL-2, TNFa, IL-b release and ROS production were increased after LPS injection. In conclusions, ROS and proinflammatory mediators produced by immune cells in response to LPS are involved in the oxidative stress of endotoxic shock. This oxidative state alters some functional characteristics of leukocytes (proliferation and NK activity)., V. M. Víctor, M. De la Fuente., and Obsahuje bibliografii