OXIDATIVE METABOLISM AND ANTIBACTERIAL ACTIVITY OF IMMUNOLOGICALLY ACTIVATED MACROPHAGES

Experiments were conducted to determine if phagocytosis-associated oxidative metabolic activity was responsible for the enhanced listericidal action of immunologically activated macrophages. Investigations into production of oxygen radicals by macrophages revealed that Listeria-immune antigen boosted macrophages produced significantly more superoxide, hydrogen peroxide, and chemiluminescence (CL) than resident, thioglycolate, or Listeria antigen elicited cells. Prolonged in vitro culture of immune boosted cells diminishes their long-term killing capacity with a parallel decrease in hydrogen peroxide production. Similarly, immune elicited macrophages cultured in excess of 29 h lose short-term listericidal activity with a concurrent diminution of CL. Scavengers of oxidative metabolites were found to be ineffective in significantly reducing the killing of Listeria in immune elicited cells. Resident murine peritoneal macrophages were rapidly rendered listericidal following exposure to lymphokine rich supernatants (LRS) derived from antigen-pulsed Listeria monocytogenes immune spleen cells. Subsequent examination of these cells showed that lymphokine activation failed to enhance the production of oxygen species. Additionally, quenchers of oxygen metabolites were unable to reduce lymphokine mediated listericidal action in resident macrophages. The production of superoxide and hydrogen peroxide by immune boosted macrophages in response to opsonized viable and heat-killed virulent Listeria monocytogenes A4413 was insignificant. In contrast, when immune elicited macrophages were exposed to Listeria A4413 a generous chemiluminescent response was noted. Similar results were obtained using avirulent Listeria monocytogenes 9037-7 and S. aureus 502A. The generation of oxidative metabolites by strains of Listeria and S. aureus 502A was also examined. Production of oxygen derived radicals was found to closely correlate with bacterial virulence. Virulent Listeria monocytogenes A4413 generated copious quantities of superoxide and hydrogen peroxide, while the avirulent Listeria 9037-7 and S. aureus 502A produced these species in greatly diminished amounts