The Contributions of Reactive Oxygen Intermediates and Reactive Nitrogen Intermediates to Listericidal Mechanisms Differ in Macrophages Activated Pre- and Postinfection

ABSTRACT The contribution of reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI) to the killing of Listeria monocytogenes by macrophages activated by addition of spleen cells from listeria-immune mice plus specific antigen was examined. When macrophages were infected with L. monocytogenes and then spleen cells were added, there was not as big a difference in listericidal activity between macrophages cultured with normal spleen cells and those cultured with immune spleen cells as expected. In this culture system, RNI was mainly involved in the macrophage intracellular killing. In macrophages first activated and then infected, a significant level of enhanced killing was observed. Blockade of ROI production drastically affected the enhanced killing ability, while inhibition of RNI production had a negligible effect. Thus, the contributions of ROI and RNI to listericidal mechanisms of macrophages were different between macrophages activated at pre- and postinfection stages.

Effects of adoptive transfer of immune spleen cells on worm growth and microfilaraemia inBrugia pahangiinfection in Mongolian gerbils

Protective immunity againstBrugia pahangiwas examined after adoptive transfer of immune spleen cells. Spleen cells obtained from gerbils at 8 weeks post-infection (p.i.) with 100 infective larvae (L3) ofB. pahangiwere transferred into naive recipients, and then 24 h later, they were infected with 100 L3ofB. pahangi. The recipients given normal spleen cells and infected by the same manner served as controls. Microfilarial counts in the circulation were monitored at designated times after infection and worm burden and the size of individual female worm were determined at 16 weeks p.i. to evaluate the effects of adoptive immunization. In addition, eosinophil responses and serum antibody titres were examined during the course of infection. In the control group, microfilariae first appeared in circulation at 9 weeks p.i. and continuously increased in number throughout the course examined. In contrast, microfilaraemia was almost completely suppressed in the group given immune spleen cells. Although worm burden was comparable between the two groups, the average size of female adult worms recovered from the adoptively immunized group was significantlysmaller than that from the control group. Eosinophil response was hastened and enhanced by adoptive transfer of immune spleen cells in the early stage of infection. Parasite- specific antibody response was also hastened by adoptive immunization. These results suggest that immune spleen cells could confer protective immunity mainly directed against adultB. pahangi.