NK cell IFNγ response to HLA-G: a role for myeloid DCs? (147.10)

Abstract

Abstract Previous studies report that stimulation of freshly isolated Natural Killer (NK) cells with soluble (but not solid-phase) ligand to KIR2DL4 results in IFNγ production. We have found that stimulation of 13-day cultured, activated, KIR2DL4-expressing NK cells with solid-phase (but not soluble) ligand to KIR2DL4 also results in NK cell IFNγ production. Human Leukocyte Antigen-G (HLA-G) has been reported to be the ligand for KIR2DL4, but controversy persists due to the irreproducibility of interactions between HLA-G (in soluble or solid-phase form) and KIR2DL4. In this study, we took freshly isolated NK cells purified by two methods, stimulated with soluble recombinant HLA-G or control, and measured IFNγ response. We observed an IFNγ response only from RosetteSep purified NK cells, and not from Easysep purified cells. Antibody cocktail analysis predicted that dendritic cells would be removed by the Easysep method but not the RosetteSep method. We confirmed the presence of CD11c+ myeloid dendritic cells (mDCs) in the RosetteSep NK cell purification and showed that removal of mDCs by cell sorting negated the IFNγ response. We further found that addition of mDCs to 13-day cultured, activated, KIR2DL4-expressing NK cells enabled IFNγ production in response to soluble HLA-G. Lastly, we have observed HLA-G tetramers binding to mDCs but not NK cells. We therefore hypothesize that mDCs bind and subsequently present “soluble” HLA-G to NK cells in order to induce an IFNγ response.