Roles of Neutrophils in Autoimmune Diseases and Cancers.

Neutrophils, a first-line defender, has a multifaceted presence in chronic inflammation, autoimmune pathology, and tumor progression. The microenvironmental cues facilitate functional plasticity and phenotypic heterogeneity to neutrophils that enable both their protective and pathogenic roles. Autoimmune diseases including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and juvenile idiopathic arthritis (JIA) display the presence of dysregulated subsets of neutrophil, such as low-density granulocytes (LDGs) that promote proinflammation and contribute to tissue damage via NETosis and type I interferon-mediated signaling. In cancer, particularly tumors, they exhibit tumor-associated neutrophils (TANs) which may polarize either towards anti-tumorigenic 'N1' or pro-tumorigenic 'N2' phenotypes based on available modulators such as TGF-β and leucine-driven epigenetic modifications. The development in neutrophil biology has introduced several novel therapeutic strategies that allow NET targeting, inhibition of chemokine receptors like CXCR2, and exploration of neutrophil-derived biomarkers for diagnosis and disease monitoring. Such findings encourage the importance of neutrophils as both effectors and therapeutic targets in inflammatory and neoplastic conditions.