Resident Kupffer cells and neutrophils drive liver toxicity in cancer immunotherapy

Immunotherapy is revolutionizing cancer treatment, but is often restricted by toxicities. What distinguishes adverse events from concomitant antitumor reactions remains poorly understood. Here, using anti-CD40-treatment in mice as a model of Th1-promoting immunotherapy, we show liver macrophages' vulnerability to promote local adverse events. Mechanistically, tissue-resident Kupffer cells mediate liver toxicity by sensing lymphocyte-derived IFN-g and producing IL-12. Conversely, dendritic cells are dispensable for toxicity but drive tumor control. Though macrophages, IL-12, and IFN-g are not necessarily toxic themselves, we find that they prompt a neutrophil response that determines the severity of tissue damage. We further show that similar inflammatory pathways characterize adverse events across tissues, following anti-PD-1 and anti-CTLA4 immunotherapies, and in humans. These findings implicate macrophages and neutrophils as mediators and effectors of aberrant inflammation in Th1-promoting immunotherapy, and suggest distinct mechanisms of toxicity and antitumor immunity. Overall design: Single cell RNA sequencing (scRNAseq) of CD45-sorted and IL-12p40-EYFP-sorted cells from tumor and liver of IL-12p40-IRES-EYFP reporter mice that were treated or not with agonist anti-CD40 immunotherapy. CD45+ cells were sorted from untreated (n=2) and anti-CD40-treated (n=2) livers; IL-12p40-EYFP+ cells were sorted from anti-CD40-treated liver (n=2) and tumor (n=3).