**Background of PADI4 Antibodies**
PADI4 (peptidyl arginine deiminase 4), a member of the PADI enzyme family, catalyzes the post-translational conversion of arginine residues to citrulline in proteins, a process termed citrullination. This modification plays roles in chromatin remodeling, gene regulation, and immune response. PADI4 is notably expressed in immune cells, including neutrophils and macrophages, and is implicated in autoimmune diseases, particularly rheumatoid arthritis (RA). In RA, excessive citrullination of proteins triggers the production of anti-citrullinated protein antibodies (ACPAs), a hallmark of the disease. Genetic polymorphisms in the *PADI4* gene are linked to increased RA susceptibility in certain populations, suggesting its role in dysregulated immune activation.
PADI4 antibodies are tools used to detect and study the expression, localization, and function of PADI4 in biological samples. They are critical in research exploring PADI4's involvement in autoimmune pathways, cancer (where PADI4 may promote tumor progression via epigenetic changes), and other inflammatory conditions. Commercial PADI4 antibodies are typically developed in hosts like rabbits or mice, targeting specific epitopes of the enzyme. Validation methods (e.g., Western blot, immunohistochemistry) ensure specificity, as cross-reactivity with other PADI isoforms (e.g., PADI2) is a common challenge. Understanding PADI4's mechanisms through antibody-based assays contributes to therapeutic strategies, including inhibitors targeting citrullination pathways in RA and cancer.