Reactive Oxygen Species Formation in Myeloid Cells

Reactive oxygen species (ROS) are chemically reactive molecules containing oxygen. In myeloid cells—including neutrophils, monocytes, macrophages, and myeloid-derived suppressor cells (MDSCs)—ROS formation is a central process for both innate immune defense and regulation of cell signaling. While primarily known for facilitating pathogen killing through oxidative burst mechanisms, ROS also act as secondary messengers in intracellular signaling pathways regulating proliferation, differentiation, apoptosis, and immune responses. Myeloid cell-derived ROS can impact the tumor microenvironment, either promoting tumorigenesis through DNA damage or modulating the immune response to support cancer progression or suppression. Key enzymes involved include NADPH oxidase (NOX2) and the mitochondrial electron transport chain. Regulation is achieved through activation triggers like PRR ligation and inflammatory cytokines, balanced by endogenous antioxidant systems. Dysregulation contributes to diseases like chronic granulomatous disease and cancer.