Optimization of peroxide production by resident macrophages

Previous reports indicated that resident macrophages produced low or nondetectable quantities of H₂O₂ (1-10 nmol H₂O₂/mg resident macrophage protein) when measured by the phenol red assay described by Pick and Mizel. However, modifications of the assay that included addition of calcium to assay solutions, alterations in cell-harvesting methods, increasing the concentration of cells analyzed, incubating the cells in ambient air, and enhancing the interactions between macrophages and particulate stimulants by centrifugation resulted in increased production of peroxide. Each variable was instrumental in improving the assay conditions and the combination of changes dramatically increased the amount of peroxide (30-60 nmol H₂O₂/mg resident macrophage protein) obtained from murine resident macrophages, making it possible to better assess the role of these cells in microbicidal killing.