Updated publication reference for PubMed record(s): 30915077. Neutrophil Extracellular Traps (NETs) are chromatin-derived extracellular structures that are expelled from neutrophils in response to infectious or inflammatory stimuli. NET DNA structures are decorated with proteins including histones, myeloperoxidase and neutrophil elastase. NETs are implicated in the development of auto-immunity in diseases including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) through the externalisation of intracellular neoepitopes e.g. dsDNA and nuclear proteins in SLE and citrullinated peptides in RA. The aim of this work was to use quantitative proteomics to identify and measure NET proteins produced by neutrophils from healthy individuals, and from patients with RA and SLE.