Expression of KIR2DS1 does not significantly contribute to NK cell cytotoxicity in HLA-C1/C2 heterozygous haplotype B donors

NK cells are functionally controlled by the killer immunoglobulin-like receptor (KIR) family that comprises inhibitory (iKIR) and activating (aKIR) members. Genetic association studies suggest that donors expressing aKIRs next to iKIRs will be superior donors in the setting of hematopoietic stem cell transplantation of patients with leukemia. However, contrary evidence states that aKIR expression may be irrelevant or even detrimental. Using a complex methodology incorporating KIR-Q-PCR, double fluorescence and viSNE analysis, we characterized subset distribution patterns and functionality in haplotype A donors which lack aKIRs and haplotype B donors that express a variety of B-specific genes. Here, we show that the alloreactive KIR2DS1+ NK cell subset in HLA-C1/C2 donors is highly responsive towards C2-expressing targets but quantitatively small and as such does not significantly contribute to cytotoxicity. Thus, we fail to find a direct link between haplotype allocation status and NK cell cytotoxicity at least in HLA-C1/C2 heterozygous donors.