Inflammasome-Independent Role for NLRP3 in Controlling Innate Antihelminth Immunity and Tissue Repair in the Lung

Abstract

Key Points Nlrp3−/− mice have enhanced early antihelminth immunity in the lung. Type 2 immunity and repair responses are dysregulated in Nlrp3−/− mice. NLRP3 plays an inflammasome-independent role during Nippostrongylus infection. Alternatively activated macrophages are essential effector cells during type 2 immunity and tissue repair following helminth infections. We previously showed that Ym1, an alternative activation marker, can drive innate IL-1R–dependent neutrophil recruitment during infection with the lung-migrating nematode, Nippostrongylus brasiliensis, suggesting a potential role for the inflammasome in the IL-1–mediated innate response to infection. Although inflammasome proteins such as NLRP3 have important proinflammatory functions in macrophages, their role during type 2 responses and repair are less defined. We therefore infected Nlrp3−/− mice with N. brasiliensis. Unexpectedly, compared with wild-type (WT) mice, infected Nlrp3−/− mice had increased neutrophilia and eosinophilia, correlating with enhanced worm killing but at the expense of increased tissue damage and delayed lung repair. Transcriptional profiling showed that infected Nlrp3−/− mice exhibited elevated type 2 gene expression compared with WT mice. Notably, inflammasome activation was not evident early postinfection with N. brasiliensis, and in contrast to Nlrp3−/− mice, antihelminth responses were unaffected in caspase-1/11–deficient or WT mice treated with the NLRP3-specific inhibitor MCC950. Together these data suggest that NLRP3 has a role in constraining lung neutrophilia, helminth killing, and type 2 immune responses in an inflammasome-independent manner.