Lipocalin-2 expression identifies an immuno-regulatory intestinal neutrophil population during GVHD

Acute graft-versus-host disease (aGVHD) is a life-threatening complication of allogeneic hematopoietic cell transplantation (allo-HCT). Strategies to promote intestinal tissue tolerance during aGVHD may improve patient outcomes. Using single-cell RNA-sequencing, we identified a Lipocalin-2 (LCN2)-expressing neutrophil population in mice with intestinal aGVHD. Transfer of LCN2-overexpressing neutrophils or treatment with recombinant LCN2 reduced aGVHD-severity, while the lack of epithelial or hematopoietic LCN2 enhanced aGVHD severity and caused microbiome alterations. Mechanistically, LCN2 induced IGF-1R signaling in macrophages via the LCN2 receptor Slc22A17, which increased IL-10 production while reducing MHC-II expression. Transfer of LCN2-pretreated macrophages reduced aGVHD severity. LCN2-treatment did not reduce graft-versus-leukemia effects. In aGVHD patients LCN2 expression correlated with IL-10 expression in intestinal biopsies. We identified a novel intestinal LCN2+ neutrophil population that reduces aGVHD-severity by decreasing MHC-II expression while increasing IL-10 production in macrophages. Administration of LCN2 presents a novel approach against aGVHD to be tested in clinical trials. Overall design: Single-cell RNA sequencing was performed on neutrophils (CD45+H2kb+CD11b+Ly6G+) residing in the terminal ileum on day 21 after allogeneic hematopoietic cell transplantation. BALB/c mice receiving 5 x 10ˆ6 BM cells with 4 x 10ˆ5 T cells from C57BL/6 donor mice developed acute GVHD, while BALB/c mice receiving only 5 x 10ˆ6 BM cells from C57BL/6 serve as a control.