Inflammasome Profiling in Human Natural Killer Cells under Pro-inflammatory Stimuli and Solid Organ Transplantation

Summary Innate immunity relies on inflammasomes as key mediators of host defense, orchestrating the release of pro-inflammatory cytokines and triggering pyroptotic cell death in response to harmful stimuli. Although inflammasome activity has been extensively studied in myeloid cells, its role in natural killer (NK) cells remains underexplored. This study demonstrates that human primary NK cells can functionally activate inflammasomes both in vitro and in vivo, including in patients undergoing organ transplantation. Ex vivo stimulation with nigericin and the dipeptidyl peptidases (DPP) inhibitor Talabostat (Val-boroPro) induces pyroptotic cell death in a subset of NK cells. This is marked by the cleavage and activation of gasdermin D, a lytic pore-forming protein essential for pyroptosis. Accompanying gasdermin D activation, significant levels of lactate dehydrogenase (LDH) and residual amounts of interleukin-18 (IL-18) are released. The detection of activated caspase-4 further indicates that these processes are mediated through non-canonical inflammasome pathways in NK cells. Notably, CD56 dim and CD56 bright NK cell subsets exhibit distinct responses to pro-inflammatory stimulation. In patients with renal dysfunction, sustained inflammasome activation, particularly involving NLRP1 and NLRP3, is observed in NK cells, with a shift toward a more pro-inflammatory phenotype following kidney transplantation. Single-cell RNA sequencing analyses further reveal persistently elevated expression of caspase-4 and gasdermin-D in transplant recipients experiencing rejection and microvascular inflammation. These findings highlight the underappreciated role of NK cells in inflammasome-driven inflammation, underscoring their importance in both basic research and clinical contexts.