Resistance of genetically selected mice to MHV3 infection is not dependent on the H2O2 release by macrophages

The genetically selected high antibody responder line of mice (H(III)) for a natural immunogen were fully susceptible to mouse hepatitis virus 3 (MHV3) and the corresponding low antibody responder mice (L(III)) were fully resistant, regardless of whether they were previously treated or not with the bacillus Calmette-Guerin (BCG). The resistance or susceptibility correlated with the virus growth in the peritoneum of mice. Peritoneal cells isolated from resistant mice released higher amounts of H2O2 after phorbol myristate acetate (PMA) stimulation than susceptible mice. No spontaneous in vitro H2O2 release by peritoneal exudate cells from H(III) mice, shown to be mostly macrophages, were observed during the MHV3 infection. In contrast, the spontaneous in vitro H2O2 release by these cells from MHV3-infected L(III) mice increased gradually, reaching a maximal value 3 days after infection, and decreased in parallel to the virus clerance from the peritoneum. The BCG treatment primed the macrophages of H(III) mice for the production of H2O2 during the MHV3 infection, but did not confer resistance against the virus infection. The data obtained suggest that the acquired capability of macrophages to release H2O2 does not participate in the anti-MHV3 activity or resistance against the MHV3 infection.

Superoxide-independent hydrogen peroxide release by activated macrophages

The present data show that freshly explanted BCG-activated mouse peritoneal macrophages release large quantities of hydrogen peroxide upon initial contact with a foreign substratum, without the requirement for other membrane stimuli such as phorbol diesters. The hydrogen peroxide detected under these conditions does not originate from extracellularly released superoxide, since 2 x 10**5 BCG-activated macrophages spontaneously released 1.6 nmol hydrogen peroxide but only 0.2 nmol superoxide. Thus, more than 90% of the hydrogen peroxide detected was not derived from extracellular superoxide dismutation. The dissociation between hydrogen peroxide and superoxide release was further demonstrated in cytochalasin B- or lidocaine-treated cells or in the absence of glucose. Under these conditions, hydrogen peroxide release was markedly inhibited while superoxide release was unaffected. These observations provide evidence that another metabolic pathway is involved in the generation and release of hydrogen peroxide during adherence and spreading of freshly explanted activated macrophages onto a substratum