KIR2DS3 is an activating killer-cell immunoglobulin-like receptor expressed on natural killer (NK) cells that recognizes HLA-C molecules 1. Unlike inhibitory KIR counterparts, KIR2DS3 does not suppress NK cell activity but instead promotes NK cell-mediated immune responses. The gene exhibits complex genetics, with two paralogous KIR2DS3 genes that can be inherited separately or together, each associated with duplicated copies of KIR2DL5, contributing to KIR haplotype diversity 1. Clinically, KIR2DS3 polymorphisms influence disease susceptibility and treatment outcomes across multiple conditions. In neuroblastoma, reduced KIR2DS3 frequency correlates with advanced disease, with early-stage patients showing higher KIR2DS3 prevalence, suggesting a protective role 2. Conversely, KIR2DS3 presence in hematopoietic stem cell transplantation donors increases relapse risk and reduces survival in myeloid leukemia 3. In hepatitis C/HIV co-infection, KIR2DS3 alleles predict treatment failure 4. Additionally, maternal KIR2DS3 constitutes a risk factor for recurrent spontaneous abortion 5, while higher KIR2DS3 frequency in syphilis patients suggests increased infection susceptibility 6. These divergent associations indicate KIR2DS3's context-dependent roles in immune regulation across infectious diseases, malignancies, and reproductive immunity.