2B4 co-engagement promotes serial degranulation and killing by human NK cells

Abstract

Activation of Natural Killer (NK) cells depends on the stimulation of a broad range of receptors. Here we use murine NIH3T3 target cells expressing defined human NK cell ligands to stimulate different aspects of NK cell activity and identify how distinct ligand-receptor interactions regulate different aspects of NK cell activation. B7H6, MICA, and CD20-bound obinutuzumab engaging NKp30, NKG2D, or CD16, respectively, were found to be potent inducers of activity in pre-stimulated NK cells. Combination of these ligands with CD48 to also stimulate 2B4 significantly increased degranulation and cytokine secretion, while PVR engaging DNAM-1 showed favorable effects only in combination with B7H6. Activating NK cell receptors were downregulated in a ligand-specific fashion, whereas CD16 and NKp46 were found to be downregulated depending on NK cell activation induced by other receptors. Co-stimulation via 2B4 in combination with either NKp30, NKG2D, or CD16 significantly enhanced NK cells to serially degranulate and kill multiple targets. Our systematic analysis unravels the complexity of different activating NK cell receptors and provides strategies to specifically tune NK cell reactivities for therapeutic applications.