Figure 2.

Models of NK Cell Alloreactivity Based on KIR and HLA Expression. Donor NK cells maintain tolerance to self through interactions between inhibitory killer immunoglobulin-like receptors (KIRs) and their cognate human leukocyte antigen (HLA) ligands expressed on healthy autologous cells. In the context of haploidentical HSCT, interactions between donor and recipient KIR and HLA mediate NK cell alloreactivity against target cells. Three models have been described which predict NK cell alloreactivity: mismatch between the donor and recipient HLA (KIR ligand model), mismatch between the donor KIR and recipient HLA (receptor-ligand model), and expression of specific donor KIR haplotypes enriched for activating KIR (KIR haplotype model). When alloreactivity is predicted in the graft-versus-host direction, donor NK cells become activated and carry out cytotoxic effector functions against the recipient’s tumor cells. Created with (Biorender.com).