The activation of macrophages in the immune response against the intracellular bacterial pathogen Francisella tularensis.

The activation of peritoneal macrophages in the course of primary infection of mice with attenuated strain of Francisella tularensis is associated with 2.5 fold increase in spontaneous INT reductase activity on day 5 after the immunization. The splenic cells of immunized mice pulsed in vitro by specific antigen secrete lymphokine that is able to induce an increase in spontaneous INT reductase activity of resident peritoneal cells. The production of spontaneous superoxide anion by peritoneal phagocytes reaches the highest level on day 5 after the immunization. It does not correlate with the results of cytotoxic or phagocytic activities at this time interval. An enhanced superoxide dismutase activity precedes an increase of superoxide anion secretion. The production of hydrogen peroxide is rising till day 7 and is related to the cytotoxic activity of peritoneal phagocytes. Concerning the testing of F. tularensis antigen as immunization agent, no changes of oxidative metabolism were detected. This might be in connection with the insufficient protection effect of killed F. tularensis vaccine. The production of reactive oxygen metabolites, probably under the control of superoxide dismutase, together with secreted lymphokines during the first days after the infection may play a regulatory role in the induction of immune response against intracellular pathogen F. tularensis.