The oral mucosa is the interface between the host immune response and the oral microbiota. In periodontal disease, the microbial plaque elicits a tissue-destructive immune response. Removal of the microbial stimulus initiates active resolution of inflammatory. Here, we use single-cell RNA-sequencing (scRNA-seq) to characterize the immune response within the oral mucosa across three distinct conditions of periodontal health, disease, and resolution in mice. We report gene expression shifts across the three conditions are driven by macrophage and neutrophils and identify a unique gene signature that characterizes resolution of disease. Macrophage subgroups are identified that demonstrate differential expansion across conditions, including a subgroup that expands during resolution with an immunoregulatory gene signature and enriched for surface marker Cd74. We validate expansion of this subgroup during resolution via flow cytometry. This work presents a robust single-cell dataset of immunological changes in the oral mucosa and identifies a resolution-associated macrophage phenotype in mucosal immunity.
© 2024 The Author(s).

Oligodendrocyte precursor cells (OPCs) are a type of glial cell that differentiates into mature oligodendrocytes, a cell type that contributes to myelination, but their roles in the pathologies are not fully understood. Activities other than differentiation into oligodendrocytes have recently been reported for OPCs present in the inflammatory milieu, but intervention studies using animal models are lacking. This study aimed to explore the role of OPCs in mouse MS model experimental autoimmune encephalomyelitis (EAE). Using inducible diphtheria toxin receptor-expressing transgenic mice, platelet-derived growth factor receptor A (PDGFRα) + OPCs were depleted in EAE mice. Surprisingly, OPC depletion in the acute phase improved clinical scores and reduced demyelination. Major histocompatibility complex (MHC) class II was reduced in the spinal cord, whereas astrocyte marker and blood–spinal cord barrier tight junction and adhesion molecule expressions were unaffected after OPC depletion. The numbers of T cells and IL17-expressing Th17 cells were decreased in the spinal cords of the OPC-depleted group. MHC class II expression in spinal cord macrophages was consistently decreased by OPC depletion. These data suggest that in the acute phase of EAE, OPCs are involved in activation of infiltrated macrophages and induce subsequent T cell activation and neuroinflammation. Although the precise mechanisms remain unclear, this implies that OPCs exist not only as the source for oligodendrocytes but also play a pivotal role in central nervous system (CNS) autoimmune inflammation. Table of Contents Image MAIN POINTS OPC depletion in the acute phase of EAE improved clinical scores and reduced demyelination. OPC depletion in the spinal cord suppressed Antigen presentation via MHC class II. OPCs are involved in activation of infiltrated macrophages and induce subsequent T cell activation and neuroinflammation.

Age-related macular degeneration (AMD) is a prevalent, chronic and progressive retinal degenerative disease characterized by an inflammatory response mediated by activated microglia accumulating in the retina. In this study, we demonstrate the therapeutically effects and the underlying mechanisms of microglial repopulation in the laser-induced choroidal neovascularization (CNV) model of exudative AMD.
The CSF1R inhibitor PLX3397 was used to establish a treatment paradigm for microglial repopulation in the retina. Neovascular leakage and neovascular area were examined by fundus fluorescein angiography (FFA) and immunostaining of whole-mount RPE-choroid-sclera complexes in CNV mice receiving PLX3397. Altered cellular senescence was measured by beta-galactosidase (SA-β-gal) activity and p16INK4a expression. The effect and mechanisms of repopulated microglia on leukocyte infiltration and the inflammatory response in CNV lesions were analyzed.
We showed that ten days of the CSF1R inhibitor PLX3397 treatment followed by 11 days of drug withdrawal was sufficient to stimulate rapid repopulation of the retina with new microglia. Microglial repopulation attenuated pathological choroid neovascularization and dampened cellular senescence in CNV lesions. Repopulating microglia exhibited lower levels of activation markers, enhanced phagocytic function and produced fewer cytokines involved in the immune response, thereby ameliorating leukocyte infiltration and attenuating the inflammatory response in CNV lesions.
The microglial repopulation described herein are therefore a promising strategy for restricting inflammation and choroidal neovascularization, which are important players in the pathophysiology of AMD.
Copyright © 2024 Song, Liao, Liu, Chen, Wang, Zhou, Zhang and Li.

The BCR allows for Ag-driven B cell activation and subsequent Ag endocytosis, processing, and presentation to recruit T cell help. Core drivers of BCR signaling and endocytosis are motifs within the receptor's cytoplasmic tail (primarily CD79). However, BCR function can be tuned by other proximal cellular elements, such as CD20 and membrane lipid microdomains. To identify additional proteins that could modulate BCR function, we used a proximity-based biotinylation technique paired with mass spectrometry to identify molecular neighbors of the murine IgM BCR. Those neighbors include MHC class II molecules, integrins, various transporters, and membrane microdomain proteins. Class II molecules, some of which are invariant chain-associated nascent class II, are a readily detected BCR neighbor. This finding is consistent with reports of BCR-class II association within intracellular compartments. The BCR is also in close proximity to multiple proteins involved in the formation of membrane microdomains, including CD37, raftlin, and Ig superfamily member 8. Known defects in T cell-dependent humoral immunity in CD37 knockout mice suggest a role for CD37 in BCR function. In line with this notion, CRISPR-based knockout of CD37 expression in a B cell line heightens BCR signaling, slows BCR endocytosis, and tempers formation of peptide-class II complexes. These results indicate that BCR molecular neighbors can impact membrane-mediated BCR functions. Overall, a proximity-based labeling technique allowed for identification of multiple previously unknown BCR molecular neighbors, including the tetraspanin protein CD37, which can modulate BCR function.
Copyright © 2024 The Authors.

Contact lens wear induces corneal parainflammation involving increased immune cell numbers after 24 hours' (CD11c+, Lyz2+, γδ-T cells) and six days' (Ly6G+ cells) wear. We investigated the time course of onset and resolution of these responses.
LysMcre or C57BL/6J mice were fitted with a contact lens (four to 48 hours). Contralateral eyes did not wear lenses. After lens removal, Lyz2+, MHC-II+ or Ly6G+ cells were examined by quantitative imaging. RT-qPCR determined cytokine gene expression.
Lens wear for 24 hours increased corneal Lyz2+ cells versus contralateral eyes approximately two-fold. Corneas remained free of visible pathology. The Lyz2+ response was not observed after four or 12 hours' wear, nor after 12 hours' wear plus 12 hours' no wear. Lens removal after 24 hours' wear further increased Lyz2+ cells (∼48% after one day), which persisted for four days, returning to baseline by seven days. Lyz2+ cells in contralateral eyes remained at baseline. MHC-II+ cells showed a similar response but without increasing after lens removal. Lens wear for 48 hours showed reduced Lyz2+ cells versus 24 hours' wear with one day discontinuation, correlating with reduced IL-1β and IL-18 gene expression. Lens wear for 24 hours did not induce Ly6G+ responses six days after removal.
Lens-induced corneal parainflammation involving Lyz2+ cells requires 24 hours' wear but persists after lens discontinuation, requiring seven days for reversal. Lens wear for 48 hours may suppress initial Lyz2+ cell and cytokine responses. The significance of parainflammation during and after lens wear remains to be determined.