Reactive oxygen species (ROS) produced by mononuclear phagocytes (MPs) are widely believed to drive tissue damage in multiple sclerosis (MS), yet the distinct roles of central nervous system (CNS)-resident versus CNS-invading MPs remain unclear. Here, we combined single-cell profiling and conditional gene targeting to map and modulate ROS production across CNS MPs in a preclinical mouse model of MS. We show that monocyte-derived macrophages (MdMs) exhibit a higher oxidative stress gene signature and produce more ROS than microglia (Mglia). Challenging previous assumptions, our findings reveal that phagocytic NADPH oxidase 2 is dispensable for neuroinflammation. In contrast, quenching mitochondrial ROS (mtROS) through mitochondria-targeted catalase (mCAT) expression in MdMs, but not in Mglia, ameliorated disease severity in acute neuroinflammation. Although core phagocyte functions were unaltered in mCAT-expressing MdMs, our results demonstrate a direct neurotoxic role of mtROS. In sum, we identify MdMs as the primary driver of ROS-mediated oxidative neurological tissue damage.

Antigen-specific B cell profiling uncovers key determinants of SARS-CoV-2 antibody breadth after infection and vaccination.

T helper 17 (TH17) cells are thought to play an important role in the pathogenesis of many autoimmune disorders, including multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). However, recent studies have suggested that interleukin-17 (IL-17) may be dispensable for the induction of EAE. Here, we use an adoptive transfer model of EAE to demonstrate that an adaptive cellular source of IL-17 is absolutely required for the induction of EAE disease. We further show that B cells can regulate the transfer of EAE disease in this context. Transcriptional profiling of TH17 cells in our model suggests that loss of IL-17A/F in T cells results in a lack of an IL-23 receptor (IL-23R)-driven signaling signature. Our data demonstrate the critical importance of an adaptive immune cellular source of IL-17A and IL-17F to mediate EAE and that IL-17 signaling is required for IL-23-mediated TH17 cell pathogenicity.

Osteoclast-mediated skull bone channel remodeling influences meningeal immune infiltration upon challenge.

Long-lived immunoglobulin E (IgE) responses against innocuous environmental and dietary antigens (Ags) are maintained by an IgG1-dominant memory B cell (MBC) compartment primed for interleukin-4 (IL-4) responsiveness. The plasticity of the MBC compartment destined for IgE class switch recombination remains poorly understood. In this work, we report critical IL-4 and IL-13 dependency for the pathogenic IgE fate of type 2-polarized MBCs in allergy. Initiation of a recall response in the absence of IL-4 and IL-13 signaling diminished the type 2 MBC phenotype in mice and humans. This permitted the emergence of long-lived Ag-specific IgG2c+ MBCs in mice. The divergence to a type 1-like response was dependent on interferon-γ signaling and arose from both unswitched and class-switched Ag-specific B cells in vivo. This reprogrammed fate was sustained even beyond therapeutic intervention, revealing fundamental insights into the plasticity of the allergen-specific recall response.

Understanding of mononuclear phagocyte (MNP) diversity in the human intestine and the alterations this compartment undergoes in inflammation remains incomplete. Here, we used single-cell RNA sequencing, cellular indexing of trancriptomes and epitopes by sequencing, flow cytometry, and imaging to explore MNP heterogeneity in human ileal and colonic laminae propriae (LPs) in health and Crohn's disease (CD). In addition to monocytes, macrophage subsets, and conventional type 1 dendritic cells (cDC1s) and cDC2s, we found a CD1c+ cDC subset with transcriptional features of DC3s. Using computational tools, we identified monocyte-to-macrophage trajectories as well as putative subset-specific DC precursors. We further showed that LP CCR7+ cDCs are increased in CD and provided evidence that these cells arise from intestinal cDC2s/DC3s but not cDC1s. Collectively, these findings extend our current understanding of intestinal MNP diversity and development, highlighting both tissue-specific and inflammation-induced changes in MNP composition and function.

T cell-dependent antibody responses have been well studied in the context of small proteins and viruses. However, how B cells acquire and process antigens from large pathogens such as parasites remains poorly understood. Here, using Plasmodium sporozoites (SPZs) as a model, we investigated the formation of protective antibody responses against the circumsporozoite protein (CSP), a vaccine antigen expressed on the surfaces of SPZs. CSP-specific B cells took up CSP and bystander surface antigens during SPZ immunization and could obtain both intramolecular and intermolecular T cell help. Furthermore, prior exposure to blood-stage parasites-which predominantly share internal but not surface antigens with SPZs-can hinder the generation of anti-CSP antibodies. Thus, spatial relationships between the target antigens can affect CD4 T cell help to B cells. These data show how B cells obtain antigen for presentation to T cells and why malaria-exposed individuals have impaired antibody responses to CSP.

Repeated dengue infections elicit broadly neutralizing antibodies that are protective against severe disease.

Chitinase-like proteins (CLPs) are established biomarkers of inflammation and airway remodeling in asthma, yet their direct contribution toward disease pathogenesis is unknown. In a mouse model of type 2/type 17 airway inflammation induced by house dust mite, ragweed, and Aspergillus fumigatus (DRA) allergens, we demonstrate that murine CLPs Ym1 (Chil3) and Ym2 (Chil4) exert distinct and potent effects on airway extracellular matrix (ECM) composition during chronic lung pathology. Using both Ym1-knockout (Chil3-/-) and Ym2-knockdown (Chil4KD/KD) mice, we found that these CLPs have fundamental roles in airway remodeling that are independent of interleukin-13 (IL-13) and IL-17A signaling pathways. Antibody-mediated inhibition of CLPs after pathology has developed reverses airway remodeling independently of chronic inflammation. However, this inhibition is not sufficient to reduce airway hyperresponsiveness (AHR) in allergic animals. Instead, the absence of CLPs increases epithelial damage and leads to a loss of bronchial epithelial integrity. This work disentangles chronic IL-13 and IL-17A signaling from the development of allergic airway pathology and reveals CLPs as orchestrators of airway remodeling that can produce both protective and adverse outcomes.

A new orally bioavailable HO-1 inhibitor enhances tumor clearance after chemotherapy in mice by enhancing the recruitment of CD8 T cells.