Neonates have increased vulnerability to life-threatening infections due to the distinct immune landscape. Interleukin (IL)-27 is a key component of this immune profile that we have previously shown to be elevated in both newborn humans and mice. IL-27 continues to increase in the serum and tissues consistent with poor outcomes during gram-negative neonatal bacterial sepsis. Presently, we dissected the IL-27 producer profile at a single-cell level using IL-27p28eGFP reporter mice in our previously established model of neonatal sepsis with luciferase-expressing K1-encapsulated Escherichia coli. Whole animal imaging regionally highlighted the spleen, liver, and lungs as key infection sites by bacterial luminescence. Flow cytometry showed that IL-27 producers increased significantly in the liver with infection and were predominantly F4/80+ and CD11b+ with subpopulations that emerged expressing additional markers. This information paired with single-cell RNA sequencing further identified the most robust populations as monocytes, monocyte-derived cells, and Kupffer cells followed by smaller populations of dendritic cells and neutrophils. The transcriptome demonstrated a diverse range of functionality amongst populations that included differential expression of genes implicated in bactericidal, metabolic, and inflammatory changes. Collectively, the transcriptome of IL-27 producers from the livers of infected animals suggests an uncoordinated mix of inflammatory and suppressive activity that may contribute to immune dysregulation characteristic of sepsis. Together, this work provides previously undescribed insight into the details of IL-27 producers during early-life infection. This further provides essential information needed to support IL-27 as a therapeutic target for neonatal bacterial sepsis.
© The Author(s) 2025. Published by Oxford University Press on behalf of The American Association of Immunologists.

The purpose of this study was to understand how the gut microbial system responds to retinal injury.
Adult C57BL/6J mice were subjected to retinal laser burns or hypotony-induced retinal detachment (RD). One, 4, and 24 hours later, gut permeability (8 male mice and 8 female mice) was assessed using Evan's blue assay and the expression of ZO-1 in intestinal epithelial cells was examined by immunofluorescence. Circulating immune cells were evaluated by flow cytometry. The feces from control and lasered mice (n = 8) were collected under strict sterile conditions and processed for 16S DNA paired-end sequencing using the Illumina platform. The impact of gut dysbiosis on retinal wound healing was evaluated following treatment with Peros antibiotics (n = 8). Retinal pathologies were examined by immunohistochemistry.
Retinal laser injury significantly altered gut microbial profiles within 1 hour (β-diversity, multi-response permutation procedure [MRPP], P = 0.05). The abundance of Lignipirellula and Faecalibacterium was 100- and 6.67-fold lower, and the abundance of Akkermansia and Colidextribacter was 3.65- and 17.72-fold higher than non-lasered controls, respectively. Retinal laser burns and RD, not sham surgery, increased gut permeability at 1 hour and 4 hours by 3.82- and 24.76-fold, respectively, disrupted intestinal epithelial ZO-1 expression, accompanied by an increased population of circulating neutrophils and monocytes (P < 0.01) at 1 hour and 4 hours. Antibiotic treatment attenuated laser-/RD-induced gut permeability and the increased neutrophils and monocytes (in RD, P < 0.05). Antibiotic treatment also significantly reduced the severity of laser-induced choroidal neovascularization (CNV; P < 0.001) and RD-mediated photoreceptor apoptosis (P < 0.01), and suppressed Gr-1+ neutrophils (CNV, P < 0.001) and Iba-1+ cell infiltration (P < 0.001).
A retina-gut axis exists. Retinal injury induces rapid gut microbial alteration, which in turn modulates innate immune cell activation and regulates the wound healing response.

SUMMARY Intraocular pressure is tightly regulated by the conventional outflow tissues, preventing ocular hypertension that leads to neurodegeneration of the optic nerve, or glaucoma. Although macrophages reside throughout the conventional outflow tract, their role in regulating intraocular pressure remains unknown. Using macrophage lineage tracing approaches, we uncovered a dual macrophage ontogeny with distinct spatial organizations across the mouse lifespan. Long-lived, resident tissue macrophages concentrated in the trabecular meshwork and Schlemm’s canal, whereas short-lived monocyte-derived macrophages, instead, were abundant around distal vessels. Specific depletion of resident tissue macrophages triggered elevated intraocular pressure and outflow resistance, linked to aberrant extracellular matrix turnover in the resistance-generating tissues of the trabecular meshwork. This dysregulated physiology and tissue remodeling were not observed when we depleted monocyte-derived macrophages. Results show ontogeny and tissue-specific macrophage function within the outflow tract, uncovering the integral homeostatic role of resident tissue macrophages in resistance-generating tissues whose dysfunction is responsible for glaucoma.

Urinary neutrophils are a hallmark of urinary tract infection (UTI), yet the mechanisms governing their activation, function, and efficacy in controlling infection remain incompletely understood. Tamm-Horsfall glycoprotein (THP), the most abundant protein in urine, uses terminal sialic acids to bind an inhibitory receptor and dampen neutrophil inflammatory responses. We hypothesized that neutrophil modulation is an integral part of THP-mediated host protection. In a UTI model, THP-deficient mice showed elevated urinary tract bacterial burdens, increased neutrophil recruitment, and more severe tissue histopathological changes compared with WT mice. Furthermore, THP-deficient mice displayed impaired urinary NETosis during UTI. To investigate the effect of THP on NETosis, we coupled in vitro fluorescence-based NET assays, proteomic analyses, and standard and imaging flow cytometry with peripheral human neutrophils. We found that THP increases proteins involved in respiratory chain, neutrophil granules, and chromatin remodeling pathways; enhances NETosis in an ROS-dependent manner; and drives NET-associated morphologic features including nuclear decondensation. These effects were observed only in the presence of a NETosis stimulus and could not be solely replicated with equivalent levels of sialic acid alone. We conclude that THP is a critical regulator of NETosis in the urinary tract, playing a key role in host defense against UTI.

The goal of therapeutic cancer vaccines and immune checkpoint therapy (ICT) is to promote T cells with anti-tumor capabilities. Here, we compared mutant neoantigen (neoAg) peptide-based vaccines with ICT in preclinical models. NeoAg vaccines induce the most robust expansion of proliferating and stem-like PD-1+TCF-1+ neoAg-specific CD8 T cells in tumors. Anti-CTLA-4 and/or anti-PD-1 ICT promotes intratumoral TCF-1- neoAg-specific CD8 T cells, although their phenotype depends in part on the specific ICT used. Anti-CTLA-4 also prompts substantial changes to CD4 T cells, including induction of ICOS+Bhlhe40+ T helper 1 (Th1)-like cells. Although neoAg vaccines or ICTs expand iNOS+ macrophages, neoAg vaccines maintain CX3CR1+CD206+ macrophages expressing the TREM2 receptor, unlike ICT, which suppresses them. TREM2 blockade enhances neoAg vaccine efficacy and is associated with fewer CX3CR1+CD206+ macrophages and induction of neoAg-specific CD8 T cells. Our findings highlight different mechanisms underlying neoAg vaccines and different forms of ICT and identify combinatorial therapies to enhance neoAg vaccine efficacy.
Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.