LY6E (lymphocyte antigen 6 family member E) is an interferon-stimulated gene that functions as a multifaceted antiviral and immunological regulator. Primarily, LY6E restricts viral entry by inhibiting spike protein-mediated membrane fusion across multiple viral families 1. The protein adopts a microtubule-like organization upon viral infection and enhances viral uncoating following endosomal escape 2. LY6E demonstrates broad antiviral activity against enveloped viruses including coronaviruses (SARS-CoV, SARS-CoV-2, MERS-CoV), respiratory syncytial virus, and flaviviruses, though not all viruses require LY6E for cellular entry 13. Mechanistically, LY6E is induced by interferon signaling and STING pathway activation, conferring cell-intrinsic protection in multiple cell types including epithelial cells and B cells 45. Clinical significance emerges across infectious and non-infectious contexts: elevated Ly6E+ neutrophils predict anti-PD1 immunotherapy response with >0.9 AUC in cancer patients 4, while LY6E expression correlates with treatment response in chr8 hepatitis B 6 and RSV infection 3. Beyond antiviral immunity, LY6E-derived transcripts promote breast cancer metastasis through EGFR pathway activation 7, highlighting complex pleiotropic roles in both protective immunity and oncogenesis.