The role of neutrophils and NETosis in autoimmune and renal diseases

Neutrophils are crucial regulators of the innate immune response and act as a first line of defence against invading microorganisms. To target microorganisms, neutrophils release extracellular structures called neutrophil extracellular traps (NETs), which externalize key autoantigens. In this Review, Gupta and Kaplan explore the contribution of neutrophils and NETs to the pathophysiology of systemic autoimmune disorders that can affect the kidneys, and discuss neutrophils as novel therapeutic targets for these diseases. Systemic autoimmune diseases are a group of disorders characterized by a failure in self-tolerance to a wide variety of autoantigens. In genetically predisposed individuals, these diseases occur as a multistep process in which environmental factors have key roles in the development of abnormal innate and adaptive immune responses. Experimental evidence collected in the past decade suggests that neutrophils — the most abundant type of white blood cell — might have an important role in the pathogenesis of these diseases by contributing to the initiation and perpetuation of immune dysregulation through the formation of neutrophil extracellular traps (NETs), synthesis of proinflammatory cytokines and direct tissue damage. Many of the molecules externalized through NET formation are considered to be key autoantigens and might be involved in the generation of autoimmune responses in predisposed individuals. In several systemic autoimmune diseases, the imbalance between NET formation and degradation might increase the half-life of these lattices, which could enhance the exposure of the immune system to modified autoantigens and increase the capacity for NET-induced organ damage. This Review details the role of neutrophils and NETs in the pathophysiology of systemic autoimmune diseases, including their effect on renal damage, and discusses neutrophil targets as potential novel therapies for these diseases.