Enteric Viruses Ameliorate Gut Inflammation via Toll-like Receptor 3 and Toll-like Receptor 7-Mediated Interferon-ß Production.

Metagenomic studies show that diverse resident viruses inhabit the healthy gut; however, little is known about the role of these viruses in the maintenance of gut homeostasis. We found that mice treated with antiviral cocktail displayed more severe dextran sulfate sodium (DSS)-induced colitis compared with untreated mice. DSS-induced colitis was associated with altered enteric viral abundance and composition. When wild-type mice were reconstituted with Toll-like receptor 3 (TLR3) or TLR7 agonists or inactivated rotavirus, colitis symptoms were significantly ameliorated. Mice deficient in both TLR3 and TLR7 were more susceptible to DSS-induced experimental colitis. In humans, combined TLR3 and TLR7 genetic variations significantly influenced the severity of ulcerative colitis. Plasmacytoid dendritic cells isolated from inflamed mouse colon produced interferon-ß in a TLR3 and TLR7-dependent manner. These results imply that recognition of resident viruses by TLR3 and TLR7 is required for protective immunity during gut inflammation.

Forkhead box protein D2 suppresses colorectal cancer by reprogramming enhancer interactions.

Somatic stem cells contribute to normal tissue homeostasis, and their epigenomic features play an important role in regulating tissue identities or developing disease states. Enhancers are one of the key players controlling chromatin context-specific gene expression in a spatial and temporal manner while maintaining tissue homeostasis, and their dysregulation leads to tumorigenesis. Here, epigenomic and transcriptomic analyses reveal that forkhead box protein D2 (FOXD2) is a hub for the gene regulatory network exclusive to large intestinal stem cells, and its overexpression plays a significant role in colon cancer regression. FOXD2 is positioned at the closed chromatin and facilitates mixed-lineage leukemia protein-4 (MLL4/KMT2D) binding to deposit H3K4 monomethylation. De novo FOXD2-mediated chromatin interactions rewire the regulation of p53-responsive genes and induction of apoptosis. Taken together, our findings illustrate the novel mechanistic details of FOXD2 in suppressing colorectal cancer growth and suggest its function as a chromatin-tuning factor and a potential therapeutic target for colorectal cancer.

Expansion of tumor-infiltrating lymphocytes from head and neck squamous cell carcinoma to assess the potential of adoptive cell therapy.

BACKGROUND: Adoptive transfer of in vitro expanded tumor-infiltrating lymphocytes (TILs) has been effective in regressing several types of malignant tumors. This study assessed the yield and factors influencing the successful expansion of tumor-infiltrating lymphocytes (TILs) from head and neck squamous cell carcinoma (HNSCC), along with their immune phenotypes. METHODS: TILs were expanded from 47 surgically resected HNSCC specimens and their metastasized lymph nodes. The cancer tissues were cut into small pieces (1-2 mm) and underwent initial expansion for 2 weeks. Tumor location, smoking history, stromal TIL percentage, human papillomavirus infection, and programmed death-ligand 1 score were examined for their impact on successful expansion of TILs. Expanded TILs were evaluated by flow cytometry using fluorescence-activated cell sorting. A second round of TIL expansion following the rapid expansion protocol was performed on a subset of samples with successful TIL expansion. RESULTS: TILs were successfully expanded from 36.2% samples. Failure was due to contamination (27.6%) or insufficient expansion (36.2%). Only the stromal TIL percentage was significantly associated with successful TIL expansion (p = 0.032). The stromal TIL percentage also displayed a correlation with the expanded TILs per fragment (r = 0.341, p = 0.048). On flow cytometry analysis using 13 samples with successful TIL expansion, CD4 + T cell dominancy was seen in 69.2% of cases. Effector memory T cells were the major phenotype of expanded CD4 + and CD8 + T cells in all cases. CONCLUSION: We could expand TILs from approximately one-third of HNSCC samples. TIL expansion could be applicable in HNSCC samples with diverse clinicopathological characteristics.

Characterization of Th17 tissue-resident memory cells in non-inflamed intestinal tissue of Crohn's disease patients.

Crohn's disease (CD) is a chronic inflammatory disorder affecting the bowel wall. Tissue-resident memory T (Trm) cells are implicated in CD, yet their characteristics remain unclear. We aimed to investigate the transcriptional profiles and functional characteristics of Trm cells in the small bowel of CD and their interactions with immune cells. Seven patients with CD and four with ulcerative colitis as controls were included. Single-cell RNA sequencing and paired T cell receptor sequencing assessed T cell subsets and transcriptional signatures in lamina propria (LP) and submucosa/muscularis propria-enriched fractions (SM/MP) from small bowel tissue samples. We detected 58,123 T cells grouped into 16 populations, including the CD4+ Trm cells with a Th17 signature and CD8+ Trm clusters. In CD, CD4+ Trm cells with a Th17 signature, termed Th17 Trm, showed significantly increased proportions within both the LP and SM/MP areas. The Th17 Trm cluster demonstrated heightened expression of tissue-residency marker genes (ITGAE, ITGA1, and CXCR6) along with elevated levels of IL17A, IL22, CCR6, and CCL20. The clonal expansion of Th17 Trm cells in CD was accompanied by enhanced transmural dynamic potential, as indicated by significantly higher migration scores. CD-prominent Th17 Trm cells displayed an increased interferon gamma (IFNγ)-related signature possibly linked with STAT1 activation, inducing chemokines (i.e., CXCL10, CXCL8, and CXCL9) in myeloid cells. Our findings underscored the elevated Th17 Trm cells throughout the small bowel in CD, contributing to disease pathogenesis through IFNγ induction and subsequent chemokine production in myeloid cells.

Geranylgeranyl pyrophosphate amplifies Treg differentiation via increased IL-2 expression to ameliorate DSS-induced colitis.

Blocking the mevalonate pathway for cholesterol reduction by using statin may have adverse effects including statin-induced colitis. Moreover, one of the predisposing factors for colitis is an imbalanced CD4+ T cell, which can be observed on the complete deletion of HMG-CoA reductase (HMGCR), a target of statins. In this study, we inquired geranylgeranyl pyrophosphate (GGPP) is responsible for maintaining the T-cell homeostasis. Following dextran sulfate sodium (DSS)-induced colitis, simvastatin increased the severity of disease, while cotreatment with GGPP, but not with cholesterol, reversed the disease magnitude. GGPP ameliorated DSS-induced colitis by increasing Treg cells. GGPP amplified Treg differentiation through increased IL-2/STAT 5 signaling. GGPP prenylated Ras protein, a prerequisite for extracellular signal-regulated kinase (ERK) pathway activation, leading to increased IL-2 production. Higher simvastatin dose increased the severity of colitis. GGPP ameliorated simvastatin-increased colitis by increasing Treg cells. Treg cells, which have the capacity to suppress inflammatory T cells and were generated through IL-2/STAT5 signaling, increased IL-2 production through prenylation and activation of the Ras/ERK pathway.

Circulatory antigen processing by mucosal dendritic cells controls CD8(+) T cell activation.

Circulatory antigens transit through the small intestine via the fenestrated capillaries in the lamina propria prior to entering into the draining lymphatics. But whether or how this process controls mucosal immune responses remains unknown. Here we demonstrate that dendritic cells (DCs) of the lamina propria can sample and process both circulatory and luminal antigens. Surprisingly, antigen cross-presentation by resident CX3CR1(+) DCs induced differentiation of precursor cells into CD8(+) T cells that expressed interleukin-10 (IL-10), IL-13, and IL-9 and could migrate into adjacent compartments. We conclude that lamina propria CX3CR1(+) DCs facilitate the surveillance of circulatory antigens and act as a conduit for the processing of self- and intestinally absorbed antigens, leading to the induction of CD8(+) T cells, that partake in the control of T cell activation during mucosal immune responses.

AMPK-SKP2-CARM1 signalling cascade in transcriptional regulation of autophagy.

Autophagy is a highly conserved self-digestion process, which is essential for maintaining homeostasis and viability in response to nutrient starvation. Although the components of autophagy in the cytoplasm have been well studied, the molecular basis for the transcriptional and epigenetic regulation of autophagy is poorly understood. Here we identify co-activator-associated arginine methyltransferase 1 (CARM1) as a crucial component of autophagy in mammals. Notably, CARM1 stability is regulated by the SKP2-containing SCF (SKP1-cullin1-F-box protein) E3 ubiquitin ligase in the nucleus, but not in the cytoplasm, under nutrient-rich conditions. Furthermore, we show that nutrient starvation results in AMP-activated protein kinase (AMPK)-dependent phosphorylation of FOXO3a in the nucleus, which in turn transcriptionally represses SKP2. This repression leads to increased levels of CARM1 protein and subsequent increases in histone H3 Arg17 dimethylation. Genome-wide analyses reveal that CARM1 exerts transcriptional co-activator function on autophagy-related and lysosomal genes through transcription factor EB (TFEB). Our findings demonstrate that CARM1-dependent histone arginine methylation is a crucial nuclear event in autophagy, and identify a new signalling axis of AMPK-SKP2-CARM1 in the regulation of autophagy induction after nutrient starvation.

IκBζ controls NLRP3 inflammasome activation via upregulation of the Nlrp3 gene.

Inflammasome activation induces the maturation and secretion of interleukin (IL)-1ß and -18, and is dependent on NF-κB signaling to induce the transcription of the inflammasome components, called the priming step. This study elucidated the role of IκBζ, an atypical IκBs (inhibitor of κB) and a coactivator of NF-κB target genes, on the activation of inflammasome. Bone marrow-derived macrophages (BMDMs) that originated from IκBζ-encoding Nfkbiz gene depletion mice presented a defect in NLRP3 inflammasome activation. In addition, the Nfkbiz+/- and Nfkbiz-/- mice significantly attenuated serum IL-1ß secretion in response to a monosodium urate injection, a NLRP3 trigger, when compared with Nfkbiz-+/+ mice. The lack of IκBζ in BMDMs produced a disability in the expression of Nlrp3 and pro-Il1ß mRNAs during the priming step. In addition, ectopic IκBζ expression enhanced the Nlrp3 promoter activity, and Nlrp3 and pro-Il1ß transcription. Overall, IκBζ controlled the activation of NLRP3 inflammasome by upregulating the Nlrp3 gene during the priming step.

CX3CR1+ Macrophages and CD8+ T Cells Control Intestinal IgA Production.

Secretory IgA is a key host defense mechanism that controls the intestinal microbiota. We investigated the role of CD11c+CX3CR1+CD64+ macrophages in IgA production in the intestine. Intestinal CX3CR1+ macrophages directly induced IgA secretion by B cells. Ag delivery to lamina propria (LP) CX3CR1+ macrophages specifically induced intestinal IgA production. The induction of IgA by CX3CR1+ macrophages required BAFF, a proliferation-inducing ligand, and TNF-α, but was surprisingly independent of TLR-mediated microbial recognition and retinoic acid signaling. IgA secretion by CX3CR1+ macrophages was enhanced by LP CD8+ T cells through the secretion of IL-9 and IL-13. CX3CR1+ macrophages and CD8+ T cells induced IgA production by B cells independently of mesenteric lymph nodes and Peyer patches. Our data reveal a previously unrecognized cellular circuitry in which LP CX3CR1+ macrophages, B cells, and CD8+ T cells coordinate the protective Ig secretion in the small intestine upon peripheral Ag delivery.

Iroquois Homeobox Protein 2 Identified as a Potential Biomarker for Parkinson's Disease.

The diagnosis of Parkinson's disease (PD) is initiated after the occurrence of motor symptoms, such as resting tremors, rigidity, and bradykinesia. According to previous reports, non-motor symptoms, notably gastrointestinal dysfunction, could potentially be early biomarkers in PD patients as such symptoms occur earlier than motor symptoms. However, connecting PD to the intestine is methodologically challenging. Thus, we generated in vitro human intestinal organoids from PD patients and ex vivo mouse small intestinal organoids from aged transgenic mice. Both intestinal organoids (IOs) contained the human LRRK2 G2019S mutation, which is the most frequent genetic cause of familial and sporadic PD. By conducting comprehensive genomic comparisons with these two types of IOs, we determined that a particular gene, namely, Iroquois homeobox protein 2 (IRX2), showed PD-related expression patterns not only in human pluripotent stem cell (PSC)-derived neuroectodermal spheres but also in human PSC-derived neuronal cells containing dopaminergic neurons. We expected that our approach of using various cell types presented a novel technical method for studying the effects of multi-organs in PD pathophysiology as well as for the development of diagnostic markers for PD.

Paneth cells as a site of origin for intestinal inflammation.

The recognition of autophagy related 16-like 1 (ATG16L1) as a genetic risk factor has exposed the critical role of autophagy in Crohn's disease. Homozygosity for the highly prevalent ATG16L1 risk allele, or murine hypomorphic (HM) activity, causes Paneth cell dysfunction. As Atg16l1(HM) mice do not develop spontaneous intestinal inflammation, the mechanism(s) by which ATG16L1 contributes to disease remains obscure. Deletion of the unfolded protein response (UPR) transcription factor X-box binding protein-1 (Xbp1) in intestinal epithelial cells, the human orthologue of which harbours rare inflammatory bowel disease risk variants, results in endoplasmic reticulum (ER) stress, Paneth cell impairment and spontaneous enteritis. Unresolved ER stress is a common feature of inflammatory bowel disease epithelium, and several genetic risk factors of Crohn's disease affect Paneth cells. Here we show that impairment in either UPR (Xbp1(ΔIEC)) or autophagy function (Atg16l1(ΔIEC) or Atg7(ΔIEC)) in intestinal epithelial cells results in each other's compensatory engagement, and severe spontaneous Crohn's-disease-like transmural ileitis if both mechanisms are compromised. Xbp1(ΔIEC) mice show autophagosome formation in hypomorphic Paneth cells, which is linked to ER stress via protein kinase RNA-like endoplasmic reticulum kinase (PERK), elongation initiation factor 2α (eIF2α) and activating transcription factor 4 (ATF4). Ileitis is dependent on commensal microbiota and derives from increased intestinal epithelial cell death, inositol requiring enzyme 1α (IRE1α)-regulated NF-κB activation and tumour-necrosis factor signalling, which are synergistically increased when autophagy is deficient. ATG16L1 restrains IRE1α activity, and augmentation of autophagy in intestinal epithelial cells ameliorates ER stress-induced intestinal inflammation and eases NF-κB overactivation and intestinal epithelial cell death. ER stress, autophagy induction and spontaneous ileitis emerge from Paneth-cell-specific deletion of Xbp1. Genetically and environmentally controlled UPR function within Paneth cells may therefore set the threshold for the development of intestinal inflammation upon hypomorphic ATG16L1 function and implicate ileal Crohn's disease as a specific disorder of Paneth cells.

Interleukin-1 (IL-1) signaling in intestinal stromal cells controls KC/ CXCL1 secretion, which correlates with recruitment of IL-22- secreting neutrophils at early stages of Citrobacter rodentium infection.

Attaching and effacing pathogens, including enterohemorrhagic Escherichia coli in humans and Citrobacter rodentium in mice, raise serious public health concerns. Here we demonstrate that interleukin-1 receptor (IL-1R) signaling is indispensable for protection against C. rodentium infection in mice. Four days after infection with C. rodentium, there were significantly fewer neutrophils (CD11b+ Ly6C+ Ly6G+) in the colons of IL-1R−/− mice than in wild-type mice. Levels of mRNA and protein of KC/CXCL1 were also significantly reduced in colon homogenates of infected IL-1R−/− mice relative to wild-type mice. Of note, infiltrated CD11b+ Ly6C+ Ly6G+ neutrophils were the main source of IL-22 secretion after C. rodentium infection. Interestingly, intestinal stromal cells isolated from IL-1R−/− mice secreted lower levels of KC/CXCL1 than stromal cells from wild-type mice during C. rodentium infection. Similar effects were found when mouse intestinal stromal cells and human nasal polyp stromal cells were treated with IL-1R antagonists (i.e., anakinra) in vitro. These results suggest that IL-1 signaling plays a pivotal role in activating mucosal stromal cells to secrete KC/CXCL1, which is essential for infiltration of IL-22-secreting neutrophils upon bacterial infection.

A mouse model of shigellosis by intraperitoneal infection.

In human and nonhuman primates, Shigella spp. cause bacillary dysentery by invading colon epithelium and promoting a strong inflammatory response; however, adult mice are resistant to oral Shigella infection. In this study, intraperitoneal challenge with virulent S. flexneri 2a (YSH6000) resulted in diarrhea and severe body weight loss in adult B6 mice. Of note, virulent S. flexneri 2a could invade and colonize not only systemic tissues but also the serosa and lamina propria region of the large intestine. In addition, epithelial shedding, barrier integrity, and goblet cell hyperplasia were found in the large intestine by 24 hours post-intraperitoneal Shigella infection. Of note, predominant expression of proinflammatory cytokines and chemokines were found in the large intestine after intraperitoneal challenge. Monocytes played a critical role in attenuating diarrhea and in providing protective efficacy against intraperitoneal Shigella infection. Most importantly, mice prevaccinated with attenuated S. flexneri 2a (SC602) strain were protected against intraperitoneal challenge with YSH6000. When taken together, these findings show that intraperitoneal challenge with virulent S. flexneri 2a can provoke bacillary dysentery and severe pathogenesis in adult mice. This model may be helpful for understanding the induction mechanism of bacillary dysentery and for evaluating Shigella vaccine candidates.

Distinct TLR-mediated pathways regulate house dust mite-induced allergic disease in the upper and lower airways.

BACKGROUND: Allergic rhinitis (AR) and asthma are 2 entities of allergic airway diseases that frequently occur together, which is referred to as united airways. In contrast to this general concept, we hypothesized that innate immunity of the upper and lower airways is respectively distinctive, because the immunologic conditions of the nasal and lung mucosa as well as the functions of the immune cells within their epithelia are different. OBJECTIVE: We wanted to identify distinctive mechanisms of innate immunity in the nose and lung mucosa, which are responsible for house dust mite (HDM)-induced AR and allergic asthma (AA), respectively. METHODS: We constructed a mouse model of AR or AA induced by sensitization and consequent provocation with HDM extracts. RESULTS: HDM-derived ß-glucans, rather than LPS, were proven to be essential to activating innate immunity in the nasal mucosa and triggering AR, which depended on Toll-like receptor 2 (TLR2), but not on TLR4; however, the LPS/TLR4 signaling axis, rather than ß-glucans/TLR2, was critical to HDM-induced AA. These differences were attributed to the specific role of ß-glucans and LPS in inducing the surface expression of TLR2 and TLR4 and their translocation to lipid rafts in nasal and bronchial epithelial cells, respectively. We also showed that dual oxidase 2-generated reactive oxygen species mediate both ß-glucan-induced TLR2 activation and LPS-induced TLR4 activation. CONCLUSIONS: We describe a novel finding of distinctive innate immunity of the nose and lungs, respectively, which trigger AR and AA, by showing the critical role of HDM-induced TLR activation via dual oxidase 2-mediated reactive oxygen species.

Langerin-expressing dendritic cells in gut-associated lymphoid tissues.

Dendritic cells (DCs) are key regulators of the immune system. They act as professional antigen-presenting cells and are capable of activating naive T cells and stimulating the growth and differentiation of B cells. According to their molecular expression, DCs can be divided into several subsets with different functions. We focus on DC subsets expressing langerin, a C-type lectin. Langerin expression is predominant in skin DCs, but langerin-expressing DCs also exist in mucosal tissue and can be induced by immunization and sometimes by nutrient deficiency. Topical transcutaneous immunization induces langerin(+)CD8 alpha(-) DCs in mesenteric lymph nodes (MLNs), which mediate the production of antigen-specific immunoglobulin A antibody in the intestine. Yet, in one recent study, langerin(+) DCs were generated in gut-associated lymphoid tissue and contributed to the suppressive intestinal immune environment in the absence of retinoic acid. In this review, we focus on the phenotypic and functional characteristics of langerin(+) DCs in the mucosal tissues, especially MLNs.

Interleukin-1 promotes coagulation, which is necessary for protective immunity in the lung against Streptococcus pneumoniae infection.

Interleukin (IL)-1 is a well-known cytokine for the initiation of innate immunity in bacterial infection. However, the underlying mechanism of IL-1 on the respiratory infection is not fully elucidated. We studied how IL-1 contributes to the host defense against Streptococcus pneumoniae. IL-1R(-/-) mice showed high mortality, local cytokine storm, and substantial infiltrates in the lower respiratory tract after intratracheal challenge with S. pneumoniae. The IL-1-deficient condition did not suppress the propagation of bacteria in the lung, although the recruitment and the bacteria-killing ability of neutrophils (CD11b(+)Ly6C(+)Ly6G(+)) were not defective compared with wild-type mice. Unexpectedly, we found that the transcription of fibrinogen alpha and gamma genes were highly activated in the lungs of wild-type mice after the infection, whereas no significant changes were found in IL-1R(-/-) mice. Of note, synthesis of fibrinogen was dependent on the IL-1-IL-6-Stat3 cascade. Treatment with recombinant fibrinogen improved survival and bacterial propagation in the IL-1R(-/-) mice and blockade of the coagulation increased the susceptibility of wild-type mice to pneumococcal pneumonia. Our findings suggest that IL-1 signaling leads to the synthesis of fibrinogen in the lung after pneumococcus infection and is followed by coagulation, which contributes to the control of bacterial infection in the pulmonary tract.

Gut microbiota-derived metabolites tune host homeostasis fate.

The gut microbiota, housing trillions of microorganisms within the gastrointestinal tract, has emerged as a critical regulator of host health and homeostasis. Through complex metabolic interactions, these microorganisms produce a diverse range of metabolites that substantially impact various physiological processes within the host. This review aims to delve into the intricate relationships of gut microbiota-derived metabolites and their influence on the host homeostasis. We will explore how these metabolites affect crucial aspects of host physiology, including metabolism, mucosal integrity, and communication among gut tissues. Moreover, we will spotlight the potential therapeutic applications of targeting these metabolites to restore and sustain host equilibrium. Understanding the intricate interplay between gut microbiota and their metabolites is crucial for developing innovative strategies to promote wellbeing and improve outcomes of chronic diseases.

Blockade of Myd88 signaling induces antitumor effects by skewing the immunosuppressive function of myeloid-derived suppressor cells.

Myd88 is an important adaptor molecule for the activation of NADPH oxidase and arginase-1, which are responsible for the suppressive function of myeloid-derived suppressor cells (MDSCs). When wild-type and Myd88(-/-) mice were subcutaneously injected with CT26 colon cancer cells expressing human Her-2/neu, tumor growth was retarded in Myd88(-/-) mice than in wild-type mice. Although the generation of CD11b(+) Gr-1(+) MDSCs was less in Myd88(-/-) mice than in wild-type mice, Myd88(-/-) mice having tumor masses still had significant quantities of MDSCs, suggesting that MDSC generation might be independent of Myd88 signaling. However, MDSCs obtained from tumor-bearing Myd88(-/-) mice failed to suppress antigen-specific proliferation of CD8(+) T cells and CD4(+) T cells, whereas MDSCs from wild-type mice significantly suppressed both types of T cells. Consistent with this, we found that the levels of costimulatory molecules and MHC class II were significantly increased in MDSCs obtained from Myd88(-/-) mice compared with wild-type mice after tumor challenge. Furthermore, CD4(+) T cells residing in tumor-draining lymph nodes of Myd88(-/-) mice secreted more TNF-α than those of wild-type mice. Finally, the blockade of Myd88 signaling by treatment with Myd88 inhibitory peptide, during later tumor stages, significantly inhibited the growth of immunogenic tumors. Overall, these data suggest that signaling through the Myd88 adaptor molecule is critical for the direct suppressive function of MDSCs and approaches to block Myd88-mediated signaling in MDSCs might be effective to inhibit the immunosuppressive function of MDSCs.

Expansion of Tfh-like cells during chronic Salmonella exposure mediates the generation of autoimmune hypergammaglobulinemia in MyD88-deficient mice.

The role of TLR signaling in linking the innate and adaptive immune systems has been a controversial issue that remains to be solved. Here, we determined whether MyD88-dependent TLR signals are required for the generation of B-cell responses during chronic Salmonella infection. Oral administration of recombinant attenuated Salmonella enterica serovar Typhimurium vaccine (RASV) strain in MyD88(-/-) mice resulted in chronic infection. Infection was accompanied by enlarged germinal centers and hypergammaglobulinemia with anti-double-stranded DNA (dsDNA)-specific Ab in sera, and the deposition of immune complexes in the kidneys, suggesting onset of autoimmunity. CD4(+) T cells expressing PD-1, CXCR5, ICOS, and IL-21 were dramatically increased in chronically infected mice, indicating the expansion of follicular helper T (Tfh)-like cells. Of note, the depletion of CD4(+) T cells completely blocked the generation of polyclonal IgG Ab in sera after oral RASV challenge. Inflammatory myeloid cells expressing CD11b and Gr-1 accumulated in high numbers in the spleen of MyD88(-/-) mice. Interestingly, the blockade of PD-1 or ICOS significantly reduced the hypergammaglobulinemia and dsDNA-specific autoantibody production. Overall, these results suggest that Tfh-like cells in chronic bacterial infection trigger autoimmune hypergammaglobulinemia in a PD-1- and ICOS-dependent manner.

Type I interferon signaling regulates Ly6C(hi) monocytes and neutrophils during acute viral pneumonia in mice.

Type I interferon (IFN-I) plays a critical role in the homeostasis of hematopoietic stem cells and influences neutrophil influx to the site of inflammation. IFN-I receptor knockout (Ifnar1⁻/⁻) mice develop significant defects in the infiltration of Ly6C(hi) monocytes in the lung after influenza infection (A/PR/8/34, H1N1). Ly6C(hi) monocytes of wild-type (WT) mice are the main producers of MCP-1 while the alternatively generated Ly6C(int) monocytes of Ifnar1⁻/⁻ mice mainly produce KC for neutrophil influx. As a consequence, Ifnar1⁻/⁻ mice recruit more neutrophils after influenza infection than do WT mice. Treatment of IFNAR1 blocking antibody on the WT bone marrow (BM) cells in vitro failed to differentiate into Ly6C(hi) monocytes. By using BM chimeric mice (WT BM into Ifnar1⁻/⁻ and vice versa), we confirmed that IFN-I signaling in hematopoietic cells is required for the generation of Ly6C(hi) monocytes. Of note, WT BM reconstituted Ifnar1⁻/⁻ chimeric mice with increased numbers of Ly6C(hi) monocytes survived longer than influenza-infected Ifnar1⁻/⁻ mice. In contrast, WT mice that received Ifnar1⁻/⁻ BM cells with alternative Ly6C(int) monocytes and increased numbers of neutrophils exhibited higher mortality rates than WT mice given WT BM cells. Collectively, these data suggest that IFN-I contributes to resistance of influenza infection by control of monocytes and neutrophils in the lung.