Inhibition of hydrogen peroxide release from activated macrophages by prior ingestion of erythrocytes or haemoglobin

Chemiluminescence activity of phagocytes from tracheal aspirates of premature infants after surfactant therapy

The effect of surfactant on the respiratory burst of phagocytic cells was studied in the tracheobronchial tract of 40 mechanically ventilated neonates (gestational age 24-37 weeks) over the first week of life. We measured the luminol-dependent chemiluminescence (CL) activity of granulocytes and macrophages isolated from tracheal aspirates in 23 preterm infants 1-6 days after administration of bovine surfactant and in 17 untreated controls. Following stimulation by the chemotactic peptide N-formylmethionylleucylphenylalanine, CL activity was not or only slightly impaired in the surfactant group. In contrast, treatment with exogenous surfactant significantly reduced CL response to opsonized zymosan (OPZ), which involves phagocytosis, for up to 6 days (p < 0.05). The impairment of CL activity seemed to be dose dependent, as repeated surfactant applications (cumulative phospholipid dose of 200 mg/kg) reduced OPZ-elicited CL activity to a greater extent than application of a single dose of 100 mg/kg. In agreement with in vitro studies, our data suggest that high-dose application of exogenous surfactant may affect the antibacterial function of phagocytic cells in the lung.

Respiratory burst capacity of activated macrophages is resistant to depression by erythrocyte phagocytosis

The present study evaluated whether macrophage activation would reduce the depression in the capacity of macrophages to produce H2O2 following EIgG phagocytosis. Macrophage activation was accomplished by exposing inflammatory rat peritoneal macrophages to 10 units of IFN gamma for 72 h. IFN gamma treatment caused a four to fivefold increase in phorbol myristate acetate (PMA)-triggered H2O2 production, but Fc receptor phagocytic function was unaltered. IFN gamma-activated macrophages were able to phagocytize a greater number of EIgG before a decrease in PMA-triggered H2O2 production was observed and the level of H2O2 production did not fall below that of untreated-inflammatory macrophages that had not received an EIgG phagocytic challenge. The depression in Fc receptor phagocytic function was unaltered with macrophage activation. These results indicate that activated macrophages are resistant to the depression of respiratory burst capacity caused by erythrocyte phagocytosis and suggests that IFN gamma treatment may be effective in preventing the impairment of host defense against bacterial infection that is associated with erythrocyte phagocytosis.

Corynebacterium parvum can reverse the depression of macrophage hydrogen peroxide production caused by erythrocyte phagocytosis

Our previous studies have shown that the phagocytosis of IgG-coated erythrocytes (EIgG) in vivo increases the mortality rate with bacterial infection, and EIgG phagocytosis in vitro depresses phorbol myristate acetate (PMA)-triggered H2O2 production. The present study was undertaken to determine if the depression of H2O2 production caused by EIgG phagocytosis could be reversed by exposing macrophages to priming agents. Macrophages exposed to 100 micrograms/ml of C. parvum, it's pyridine-soluble extract (PE), or the pyridine extract residue (PER) for 1 hr showed an enhanced production of H2O2 in response to PMA triggering. The priming effect of C. parvum, PE, and PER lasted for 3-6 hr. 18 hr after exposure to C parvum or PER, PMA-triggered H2O2 production was depressed, however PE did not have this effect. The priming effect of C parvum was not prevented by cycloheximide. EIgG phagocytosis caused a dose dependent depression of PMA-triggered H2O2 production. When macrophages were exposed to C. parvum, PE, or PER following EIgG phagocytosis, the priming of PMA-triggered H2O2 production was reduced but H2O2 production was maintained at levels equal to or greater than that of control macrophages. These results show that phagocytosis did not prevent the action of priming agents on macrophage respiratory burst capacity, and suggests that such agents may preserve macrophage bactericidal function following phagocytosis.

Macrophage hydrogen peroxide production and phagocytic function are decreased following phagocytosis mediated by Fc receptors but not complement receptors

Previous in vivo and in vitro studies have shown that the phagocytosis of IgG-coated erythrocytes results in a depression of macrophage function. The present study compared the effect of phagocytosis mediated by Fc receptors with that mediated by complement receptors. The phagocytosis of IgG-coated erythrocytes by elicited peritoneal macrophages depressed their capacity to produce hydrogen peroxide as well as phagocytic function. Phagocytosis of erythrocytes coated with IgM and complement had neither of these effects. These results implicate the intracellular signaling that results from Fc receptor mediated phagocytosis in the depression of macrophage function that is caused by phagocytosis.