APOD (apolipoprotein D) is a 25-30 kDa glycosylated lipocalin family protein 1 characterized by a conserved eight-stranded β-barrel structure that forms a cup-shaped ligand-binding pocket 2. As a multi-ligand transporter, APOD binds and transports small hydrophobic molecules including cholesterol, arachidonic acid, bilirubin, and progesterone 31. Its primary functions encompass lipid metabolism, arachidonic acid trafficking, and modulation of eicosanoid production 14. APOD regulates oxidative stress and inflammation by sequestering arachidonic acid and limiting pro-inflammatory mediator generation 4. The protein exhibits neuroprotective properties and accumulates at sites of nervous system regeneration and in cerebrospinal fluid during neurodegenerative conditions like Alzheimer's disease 31. Disease relevance includes elevated expression in Alzheimer's disease, Parkinson's disease, cancers, and stroke 1. In prostate tissue, APOD+ peri-epithelial fibroblasts participate in stromal-epithelial interactions 5, while in oral squamous cell carcinoma, APOD+ myofibroblastic cancer-associated fibroblasts foster immunomodulatory stromal niches 6. Notably, elevated ApoD in aging drives mitophagy during influenza infection, impairing antiviral immune responses 7, suggesting therapeutic potential through ApoD inhibition in age-related infectious disease vulnerability.