IFNA5 (interferon alpha 5) is a type I interferon cytokine produced by macrophages with critical roles in antiviral and immune responses 1. The protein functions through type I interferon receptor binding and stimulates production of protein kinase and oligoadenylate synthetase, triggering antiviral defense mechanisms. IFNA5 activates multiple immune cell populations including B cells, T cells, and natural killer cells, contributing to both innate and adaptive immune responses 2. Clinically, IFNA5 genetic variants are associated with susceptibility to severe viral infections. IFNA5 polymorphisms (rs10757212, rs758236) show significant association with respiratory syncytial virus bronchiolitis severity in infants, particularly through innate immune pathways 3. In systemic lupus erythematosus nephritis, tubulointerstitial IFNA5 expression correlates with proteinuria levels, implicating type I interferon dysregulation in autoimmune kidney disease 2. Additionally, elevated circulating IFNA5 associates with concentric left ventricular remodeling in women, suggesting a sex-specific role in cardiovascular pathology and heart failure development 4. IFNA5 polymorphisms also influence susceptibility to Crimean-Congo hemorrhagic fever and appear as a novel melanoma susceptibility gene through immune pathway dysregulation 5. IFNA5 expression is upregulated during liver regeneration through estrogen receptor-β signaling, supporting hepatic progenitor differentiation 1.