International immunology最新文献

Interactions between neurons and microglia are essential for various brain functions under both healthy and pathological states. Microglia have classical functions as immune cells, causing cerebral inflammation, whereas their reparative roles after acute cerebral inflammation have recently attracted attention. In the healthy brain state, microglia contribute to homeostasis and brain tissue development. Microglia regulate neuronal activity by responding to molecules derived from neurons and eliminating excess synapses to achieve normal brain development and maintain a homeostatic brain environment. Microglia are also involved in neuronal information processing, such as learning and memory, by modulating synaptic remodeling and neurogenesis. In contrast, aging alters brain homeostasis and increases vulnerability to neurodegenerative pathologies through changes in interactions between neurons and microglia. Microglia exert diverse functions in neurological and psychiatric diseases. Microglia are responsible for rapid inflammatory responses by receiving abnormal signals from injured brain cells. Excess neuroinflammation mediated by disease-associated microglia exacerbates the pathology of central nervous system (CNS) diseases. Recent studies have also revealed the roles of microglia in improving pathologies through the phagocytosis of neurotoxic proteins and damaged or excess synapses. This review highlights the interaction between neurons and microglia in both healthy and pathological brain states. Understanding these interactions could lead to the development of therapeutic strategies by regulating the pathologies underlying various CNS disorders.

Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system (CNS) characterized by neuroinflammation, demyelination, and neurodegeneration. Among disease-modifying therapies (DMTs), sphingosine 1-phosphate (S1P) receptor (S1PR) modulators such as fingolimod, also known as FTY720, have been shown to exert therapeutic effects through direct CNS actions at S1PRs (e.g. S1P1) expressed by astrocytes, beyond the originally proposed mechanism action (MOA) of lymphocyte sequestration. This review highlights the emerging evidence linking S1P signaling to the vitamin B12 pathway, including transcobalamin 2 (TCN2) and CD320. Functional interaction between S1P1 signaling and CD320 expression was discovered by examining gene expression changes in immediate-early astrocytes (ieAstrocytes), the primary CNS cell type activated in response to neuroinflammatory stimuli. This discovery led to the identification of the physical interaction between fingolimod/sphingosine and TCN2 and the potentiation of CD320 internalization by this complex. These findings underscore the importance of CNS vitamin B12 levels in MS and likely other neurological diseases and help to explain the long-appreciated shared neurological symptoms between vitamin B12 deficiency and MS. Future research should investigate therapeutic strategies targeting the crosstalk between the sphingolipid and vitamin B12 pathways to enhance CNS vitamin B12 availability, which can promote neuroprotection in MS and related diseases.

Neuropathic pain arises from injury or disease to the sensory nervous system and is characterized by intense pain that is disproportionate to the stimulus. However, effective treatments remain limited, highlighting an urgent need for novel therapeutic approaches. Over the past two decades, studies have revealed that microglia-resident macrophages in the central nervous system-play an essential role in the development of neuropathic pain. In the dorsal horn of the spinal cord, microglia respond to nerve injury by altering cellular function and interacting with surrounding cells to enhance neuronal excitability that underlies pain hypersensitivity. This review summarizes the microglia-neuron interactions that occur in the spinal dorsal horn after peripheral nerve injury and explores recent findings on the potential of microglia to alleviate neuropathic pain.

Upon antigen recognition, T cells undergo rapid cell proliferation and differentiation, which is accompanied by a drastic change in cellular metabolism. The ADP-ribosylation factor (Arf) pathway contributes to cellular homeostasis by orchestrating vesicle trafficking, and our previous study using mice lacking both Arf1 and Arf6 (Arf-KO) revealed that Th17-mediated autoimmune diseases were markedly suppressed in Arf-KO mice though the precise mechanism remained elusive. Here, we show that the Arf pathway modulates cellular metabolism in T-cell activation and survival. We found that the lack of Arf1 and Arf6 resulted in hyper-activation of mTOR complex 1 (mTORC1), a master regulator of cellular metabolism, as well as unresolved endoplasmic reticulum (ER) stress, leading to exaggerated apoptosis during T-cell activation. We further demonstrated that treatment with IL-21, a potent inducer of Tfh differentiation, rescued Arf-KO T cells from apoptosis by attenuating ER stress in vitro. Accordingly, antigen-specific antibody production and host defenses against infections such as Leishmania major or Heligmosomoides polygyrus infections were significantly preserved in Arf-KO mice. Taken together, these findings provide mechanistic insights linking the Arf pathway with T-cell homeostasis during activation and identify the Arf pathway as an ideal therapeutic target for autoimmune diseases with a low risk of opportunistic infections.

Despite the importance of o6-methylguanine-DNA methyltransferase (MGMT) (a DNA repair enzyme) in cancer cells, the impacts of MGMT in macrophages are still unknown. In mgmt null mice (mgmtflox/flox; LysM-Crecre/-; mgmt deletion only in macrophages), subcutaneous administration of MC38 (a murine colon cancer) induced smaller tumors with lower intratumoral CD206-positive cells (mostly M2-like macrophages) than the tumors in littermate controls (mgmt control) (mgmtfl/fl; LysM-Cre-/-), as indicated by immunohistochemistry and flow cytometry. Then, bone marrow-derived macrophages were incubated with lipopolysaccharide (LPS) (M1 polarization), IL-4 (M2 polarization), MC38-conditioned media (tumor-associated macrophages; TAMs), and control media (control). In comparison with control, mgmt was upregulated in all activated cells (M1, M2, and TAMs), with the most prominent in M1. Less prominent M1 pro-inflammation (lower IL-1β and iNOS expression) and M2 polarization (lower Arg-1 expression) in mgmt null macrophages compared with mgmt control were observed. The tumoricidal activity was demonstrated only in M1 (but not M2 and TAMs), and mgmt control M1 was more prominent than mgmt null M1, as evaluated by flow cytometry using flexible 780 viable dye. There was reduced maximal respiration (extracellular flux analysis) with more prominent cell injuries, as indicated by cell-free DNA, oxidative stress (malondialdehyde), and DNA break (phosphohistone H2AX immunohistochemistry), in TAMs from mgmt null when compared with mgmt control. In conclusion, TAM transformation required cell energy and induced DNA injury, which needed the MGMT enzyme for DNA repair. Without MGMT, the abundance of TAMs was too low to promote cancer growth. The use of MGMT inhibitors for cancers is encouraged.

Lipids play fundamental roles in life. In essence, "phospholipase A2" (PLA2) indicates a group of enzymes that release fatty acids and lysophospholipids by hydrolyzing the sn-2 position of glycerophospholipids. To date, more than 50 enzymes that possess PLA2 or related lipid-metabolizing activities have been identified in mammals and are subdivided into several families in terms of their structures, catalytic mechanisms, tissue/cellular localizations, and evolutionary relationships. Among the PLA2 superfamily, the secreted PLA2 (sPLA2) family contains 11 isoforms in mammals, each of which has unique substrate specificity and tissue/cellular distributions. Recent studies using gene-manipulated (knockout and/or transgenic) mice for a full set of sPLA2s have revealed their diverse roles in immunity, metabolism, and other biological events. Application of mass spectrometric lipidomics to these mice has allowed the identification of target substrates and products of individual sPLA2s in tissue microenvironments. In principle, sPLA2s hydrolyze extracellular phospholipids such as those in extracellular vesicles, microbes, lipoproteins, surfactants, and ingested foods, as well as phospholipids in the plasma membrane of activated or damaged cells, thereby exacerbating or ameliorating various diseases. The actions of sPLA2s are dependent on, or independent of, the generation of free fatty acids, lysophospholipids, or their metabolites (lipid mediators) according to pathophysiological contexts. In this review, I will make an overview of recent understanding of the unexplored immunoregulatory roles of sPLA2s and their underlying lipid pathways, especially focusing on their unique actions on extracellular vesicles, activated/damaged cells, and gut microbiota.

Autoimmune rheumatic diseases (AIRDs) encompass a spectrum of disorders with a partially understood pathogenesis. A role for polyomaviruses in AIRDs occurrence has been reported. However, the involvement of Merkel cell polyomavirus (MCPyV), the main causative factor of Merkel cell carcinoma (MCC), an aggressive skin neoplasm related to immunosuppression, in AIRDs is unknown. The prevalence/serological profiles of immunoglobulin G (IgG) antibodies to MCPyV large and small T (LT/sT) oncoproteins and viral capsid proteins 1 and 2 (VP1/2) were investigated herein in 540 immunosuppressive treatment-naive AIRD patients, encompassing 447 rheumatoid arthritis (RA) and 93 ankylosing spondylitis (AS) patients by seven MCPyV-specific immunoassays. Control sera from 500 healthy subjects (HS) and 128 MCC patients were included. MCPyV DNA and LT/VP1 mRNAs were evaluated in peripheral blood mononuclear cells (PBMCs) from 75 randomly selected AIRD patients. AIRD patients exhibited higher prevalence and levels (optical densities) of serum anti-oncoprotein IgGs (12%-13%, 0.2-0.6) compared to HS (2%-7%, 0.1-0.4), but lower than MCC patients (70%-83%, 0.2-0.7) (P < .05), with the increase being more pronounced in AS (24%-29%, 0.3-0.8) than in RA (9%-11%, 0.2-0.8) (P < .05). Conversely, similar rates and levels of serum anti-capsid proteins IgGs were determined in most cases between study and control groups (60%-73%, 0.1-0.3) (P > .05). Moreover, receiver operating characteristic (ROC) curves indicated that the MCPyV serology can discriminate AIRD patients from HS (P < .0001). A fraction (11%) of AIRD PBMCs tested MCPyV DNA (7.4 ± 2.6 [copy/104 cells]) and mRNA-positive (0.5-0.1 [1/ΔCt]), while matched sera showed high rates and levels of anti-oncoproteins IgGs (38%-75%, 0.2-2). Our study provides the first evidence that AIRD patients are immunologically responsive to MCPyV oncoproteins, with a fraction of these patients presenting an increased presentation of MCPyV LT and sT antigens, possibly due to viral LT/sT oncogene expression in their PBMCs. These data suggest an association between MCPyV infection and AIRDs pathogenesis.

Immunity to viral infections is generally studied in isolation by measuring immune responses towards a single virus. However, concurrent or sequential viral co-infections can occur in a single host. Viral co-infections can impact anti-viral immunity by altering protective responses and driving immunopathology. Understanding immune mechanisms towards co-infections with unrelated viruses is highly relevant to treatment and prevention. There is, however, a paucity of data on immune responses towards viral co-infections, especially with unrelated viruses. Most commonly studied viral co-infections include chronic viruses, such as hepatitis B, hepatitis C, and human immunodeficiency virus, as well as viruses infecting the same tissues, including respiratory viral co-infections. However, the immunological consequences of co-infections with unrelated acute viruses are less understood, especially for viruses affecting different anatomical sites. As co-infecting viruses can have a more pronounced impact on human health compared to infection with a single virus, understanding immune responses and, especially, the impact of timing, sequence, and location of viral co-infections is of key importance. This review provides an overview of the current knowledge on acute viral co-infections with unrelated viruses, underpinning immune mechanisms, and implications for vaccination regimens.

Chronic rhinosinusitis (CRS) is an inflammatory disease of the upper respiratory tract. Although previously classified based on the presence or absence of nasal polyps, it is now commonly classified by endotype. Eosinophilic CRS (ECRS) is based on type 2 inflammation and the formation of intractable nasal polyps with eosinophil infiltration. Endoscopic surgery is the preferred treatment modality; however, recurrent cases are common. The central compartment of the nasal cavity has been implicated in these recurrences. Notably, the middle turbinate is considered crucial, but discussions have primarily focused on its anatomical significance. To date, there lacks a biochemical perspective on the role of the middle turbinate in recurrence. In this study, we evaluated the role of the middle turbinate as a source of inflammation in ECRS. Differences in gene expression between ECRS and non-ECRS (NECRS) middle turbinates were evaluated using RNA sequencing. Gene changes induced by MMP-9 stimulation of human nasal epithelial cells were also evaluated by RNA sequencing. Comprehensive analysis showed an enhanced IL-4 signaling pathway in the ECRS middle turbinate. Additionally, gene expression of matrix metalloproteinase-9 (MMP-9) was higher in the middle turbinates of patients with ECRS than in those with NECRS (P = .002). Furthermore, MMP-9 has been found to act on human nasal epithelial cells to enhance pathways such as IL-17, IL-6, and S100 family signaling. MMP-9 in the central compartment of the nasal cavity exacerbates ECRS by induction mixed-type 2 inflammation and airway remodeling.