| Abstract: | The oxidative metabolism (chemiluminescence and H2O2 release) and phagocytic activity of mouse peritoneal macrophages during chronic infections induced by Mycobacterium intracellulare and more acute infections due to Listeria monocytogenes were studied. In M. intracellulare infections, macrophage chemiluminescence in response to phorbol myristate acetate (PMA) was greatest at around 2 weeks, with a 1 week lag phase after infection, while the PMA-triggered H2O2 release was markedly enhanced even 1 d after challenge, and remained high thereafter for up to 10 weeks. The pattern of changes in the phagocytic activity of host macrophages in response to latex beads during this infection resembled the pattern seen with macrophage H2O2 release. In the L. monocytogenes infections, the PMA-triggered chemiluminescence of the host macrophages increased 4 d (in a sublethal infection) and 2 d (in a lethal infection) after bacterial challenge, whereas the PMA-triggered H2O2 release was markedly enhanced as early as 1 d after infection and the elevated level persisted until either the bacteria were eliminated or the animals died. The patterns of changes in phagocytic activity of the host macrophages during L. monocytogenes infection at sublethal and lethal doses differed. In the former, phagocytosis was most active in the early phase of infection, with a peak around day 2, followed by a rapid decrease; in the latter, the phagocytic ability increased more slowly, and remained elevated until the animals died. The results suggest that the macrophages induced by M. intracellulare are in a more activated state than are those induced by L. monocytogenes. |
