ULBP3 is an NKG2D ligand that functions as a key activator of natural killer cell-mediated cytotoxicity 1. As a stress-induced protein expressed on cell surfaces, ULBP3 binds the NKG2D receptor present on NK cells and various T cell subsets, triggering immune responses against infected or aberrant cells 2. In autoimmunity, ULBP3 expression is markedly upregulated in lesional tissue during active disease; genome-wide association studies identified the ULBP gene cluster as a novel susceptibility locus for alopecia areata, with ULBP3 levels significantly elevated in affected hair follicles and correlating with disease progression 13. Conversely, pathogens have evolved evasion mechanisms targeting ULBP3: human polyomaviruses JCV and BKV express identical microRNAs that downregulate ULBP3 to escape NK cell recognition 2, while human CMV's UL142 protein sequesters ULBP3 intracellularly, preventing surface expression and protecting infected cells from NK-mediated killing 4. Therapeutically, arming oncolytic viruses with ULBP3 enhances anti-tumor immunity in immunosuppressive environments 5, and EHMT2 inhibition increases ULBP3 expression to promote NK cell-dependent tumor control 6. Environmental factors also modulate ULBP3; cigarette smoke-induced DNA hypermethylation decreases ULBP3 expression in airway epithelium, impairing antiviral defenses 7.