Characterization of KIR NK Cell Subsets with a Monoclonal Antibody Selectively Recognizing KIR2DL1 and Blocking the Specific Interaction with HLA-C

The phenotypic identification of different NK cell subsets allows more in-depth characterization of KIR repertoire and function, which are of potential interest in KIR and disease association studies. KIR genes are highly polymorphic, but a great homology exists among the various sequences and few monoclonal antibodies (mAbs) specifically recognize a single KIR. This is the case of HP-DM1 which was demonstrated by analysis of cell transfectants and epitope mapping to be exclusively KIR2DL1-specific, covering all allotypes identified to date, except for KIR2DL1*022 and *020, and also to react with KIR2DS1*013. Here, we compared in immunofluorescence analyses the staining of HP-DM1 with other available mAbs to precisely identify KIR2DL1 NK cells in potential donors for αβT/B-depleted haplo-HSCT, with known KIR genotype. HP-DM1 mAb was used in combination with EB6 or 11PB6 (anti-KIR2DL1/S1 and anti-KIR2DL3*005), 143211 (anti-KIR2DL1/S5), and HP-MA4 (anti-KIR2DL1/S1/S3/S5) mAbs, allowing the accurate identification of different KIR NK cell subsets. These phenotypic evaluations appeared useful to dissect the expression pattern of various KIR2D in NK cells from KIR2DL3*005 individuals, particularly if KIR2DS1 is present. HP-DM1 mAb remarkably refined NK cell phenotyping of donors carrying KIR2DS5, either in the centromeric or telomeric region. Functional assays with KIR2DL1 /S1 /S5 NK cells confirmed that only HP-DM1 exclusively reacts with KIR2DL1. Finally, we demonstrated that HP-DM1 mAb blocked KIR2DL1 recognition of C2 HLA-C. Altogether, the data support that HP-DM1 is a unique reagent valuable for characterizing KIR NK cell subsets.