AUTHOR=Lin Weiji , Shen Pan , Song Yaqin , Huang Ying , Tu Shenghao TITLE=Reactive Oxygen Species in Autoimmune Cells: Function, Differentiation, and Metabolism JOURNAL=Frontiers in Immunology VOLUME=Volume 12 - 2021 YEAR=2021 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2021.635021 DOI=10.3389/fimmu.2021.635021 ISSN=1664-3224 ABSTRACT=Accumulated reactive oxygen species (ROS) directly contribute to biomacromolecule damage and influence various inflammatory responses. ROS act as mediator between innate and adaptive immune cells, thereby influencing the antigen-presenting process that results in T cell activation. Evidence from patients with chronic granulomatous disease and mouse models support the function of ROS in preventing abnormal autoimmunity; for example, by supporting maintenance of macrophage efferocytosis and T helper 1/T helper 2 and T helper 17/ regulatory T cell balance. The failure of many anti-oxidation treatments indicates that ROS cannot be considered entirely harmful. Indeed, enhancement of ROS may sometimes be required. In a mouse model of rheumatoid arthritis (RA), absence of NOX2-derived ROS led to higher prevalence and more severe symptoms. In patients with RA, naïve CD4+ T cells exhibit inhibited glycolysis and enhanced pentose phosphate pathway (PPP) activity, leading to ROS exhaustion. In this “reductive” state, CD4+ T cell immune homeostasis is disrupted, triggering joint destruction, together with oxidative stress in the synovium.