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Tissue damage and repair are hallmarks of inflammation. Despite a wealth of information on the mechanisms that govern tissue damage, mechanistic insight into how inflammation affects repair is lacking. Here, we investigated how interferons influence tissue repair after damage to the intestinal mucosa. We found that type III, not type I or type II, interferons delay epithelial cell regeneration by inducing the upregulation of Z-DNA-binding protein 1 (ZBP1). Z-nucleic acids formed following intestinal damage are sensed by ZBP1, leading to caspase-8 activation and the cleavage of gasdermin C (GSDMC). Cleaved GSDMC drives epithelial cell death by pyroptosis and delays repair of the large or small intestine after colitis or irradiation, respectively. The type III interferon/ZBP1/caspase-8/GSDMC axis is also active in patients with inflammatory bowel disease (IBD). Our findings highlight the capacity of type III interferons to delay gut repair, which has implications for IBD patients or individuals exposed to radiation therapies., Competing Interests: Declaration of interests I.Z., A.B., and S.B.S. have submitted a patent related to the matter of this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Endo-lysosomes transport along microtubules and clustering in the perinuclear area are two necessary steps for microbes to activate specialized phagocyte functions. We report that RUN and FYVE domain-containing protein 3 (RUFY3) exists as two alternative isoforms distinguishable by the presence of a C-terminal FYVE domain and by their affinity for phosphatidylinositol 3-phosphate on endosomal membranes. The FYVE domain-bearing isoform (iRUFY3) is preferentially expressed in primary immune cells and up-regulated upon activation by microbes and Interferons. iRUFY3 is necessary for ARL8b + /LAMP1+ endo-lysosomes positioning in the pericentriolar organelles cloud of LPS-activated macrophages. We show that iRUFY3 controls macrophages migration, MHC II presentation and responses to Interferon-γ, while being important for intracellular Salmonella replication. Specific inactivation of rufy3 in phagocytes leads to aggravated pathologies in mouse upon LPS injection or bacterial pneumonia. This study highlights the role of iRUFY3 in controlling endo-lysosomal dynamics, which contributes to phagocyte activation and immune response regulation., (© 2023. The Author(s).)

Objective: In the management of patients with IBD, there is a need to identify prognostic markers and druggable biological pathways to improve mucosal repair and probe the efficacy of tumour necrosis factor alpha biologics. Vnn1 is a pantetheinase that degrades pantetheine to pantothenate (vitamin B 5 , a precursor of coenzyme A (CoA) biosynthesis) and cysteamine. Vnn1 is overexpressed by inflamed colonocytes. We investigated its contribution to the tolerance of the intestinal mucosa to colitis-induced injury., Design: We performed an RNA sequencing study on colon biopsy samples from patients with IBD stratified according to clinical severity and modalities of treatment. We generated the VIVA mouse transgenic model, which specifically overexpresses Vnn1 on intestinal epithelial cells and explored its susceptibility to colitis. We developed a pharmacological mimicry of Vnn1 overexpression by administration of Vnn1 derivatives., Results: VNN1 overexpression on colonocytes correlates with IBD severity. VIVA mice are resistant to experimentally induced colitis. The pantetheinase activity of Vnn1 is cytoprotective in colon: it enhances CoA regeneration and metabolic adaptation of colonocytes; it favours microbiota-dependent production of short chain fatty acids and mostly butyrate, shown to regulate mucosal energetics and to be reduced in patients with IBD. This prohealing phenotype is recapitulated by treating control mice with the substrate (pantethine) or the products of pantetheinase activity prior to induction of colitis. In severe IBD, the protection conferred by the high induction of VNN1 might be compromised because its enzymatic activity may be limited by lack of available substrates. In addition, we identify the elevation of indoxyl sulfate in urine as a biomarker of Vnn1 overexpression, also detected in patients with IBD., Conclusion: The induction of Vnn1/VNN1 during colitis in mouse and human is a compensatory mechanism to reinforce the mucosal barrier. Therefore, enhancement of vitamin B 5 -driven metabolism should improve mucosal healing and might increase the efficacy of anti-inflammatory therapy., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

Severe acute malnutrition (SAM) is a multifactorial disease affecting millions of children worldwide. It is associated with changes in intestinal physiology, microbiota, and mucosal immunity, emphasizing the need for multidisciplinary studies to unravel its full pathogenesis. We established an experimental model in which weanling mice fed a high-deficiency diet mimic key anthropometric and physiological features of SAM in children. This diet alters the intestinal microbiota (less segmented filamentous bacteria, spatial proximity to epithelium), metabolism (decreased butyrate), and immune cell populations (depletion of LysoDC in Peyer's patches and intestinal Th17 cells). A nutritional intervention leads to a fast zoometric and intestinal physiology recovery but to an incomplete restoration of the intestinal microbiota, metabolism, and immune system. Altogether, we provide a preclinical model of SAM and have identified key markers to target with future interventions during the education of the immune system to improve SAM whole defects., Competing Interests: The authors declare no competing interests., (© 2023 The Author(s).)

Thymically-derived Foxp3 + regulatory T cells (T reg ) critically control immunological tolerance. These cells are generated in the medulla through high affinity interactions with medullary thymic epithelial cells (mTEC) expressing the Autoimmune regulator (Aire). Recent advances have revealed that thymic T reg contain not only developing but also recirculating cells from the periphery. Although Aire is implicated in the generation of Foxp3 + T reg , its role in the biology of recirculating T reg remains elusive. Here, we show that Aire regulates the suppressive signature of recirculating T reg independently of the remodeling of the medullary 3D organization throughout life where T reg reside. Accordingly, the adoptive transfer of peripheral Foxp3 + T reg in Aire KO recipients led to an impaired suppressive signature upon their entry into the thymus. Furthermore, recirculating T reg from Aire KO mice failed to attenuate the severity of multiorgan autoimmunity, demonstrating that their suppressive function is altered. Using bone marrow chimeras, we reveal that mTEC-specific expression of Aire controls the suppressive signature of recirculating T reg . Finally, mature mTEC lacking Aire were inefficient in stimulating peripheral T reg both in polyclonal and antigen-specific co-culture assays. Overall, this study demonstrates that Aire confers to mTEC the ability to restimulate recirculating T reg , unravelling a novel function for this master regulator in T reg biology., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Inflammation is a defence response to tissue damage that requires tight regulation in order to prevent impaired healing. Tissue-resident macrophages have a key role in tissue repair 1 , but the precise molecular mechanisms that regulate the balance between inflammatory and pro-repair macrophage responses during healing remain poorly understood. Here we demonstrate a major role for sensory neurons in promoting the tissue-repair function of macrophages. In a sunburn-like model of skin damage in mice, the conditional ablation of sensory neurons expressing the Gα i -interacting protein (GINIP) results in defective tissue regeneration and in dermal fibrosis. Elucidation of the underlying molecular mechanisms revealed a crucial role for the neuropeptide TAFA4, which is produced in the skin by C-low threshold mechanoreceptors-a subset of GINIP + neurons. TAFA4 modulates the inflammatory profile of macrophages directly in vitro. In vivo studies in Tafa4-deficient mice revealed that TAFA4 promotes the production of IL-10 by dermal macrophages after UV-induced skin damage. This TAFA4-IL-10 axis also ensures the survival and maintenance of IL-10 + TIM4 + dermal macrophages, reducing skin inflammation and promoting tissue regeneration. These results reveal a neuroimmune regulatory pathway driven by the neuropeptide TAFA4 that promotes the anti-inflammatory functions of macrophages and prevents fibrosis after tissue damage, and could lead to new therapeutic perspectives for inflammatory diseases.

Sjögren's syndrome (SS) is a chronic systemic autoimmune disease that affects predominately salivary and lacrimal glands. SS can occur alone or in combination with another autoimmune disease like systemic lupus erythematosus (SLE). Here we report that TLR7 signaling drives the development of SS since TLR8-deficient (TLR8ko) mice that develop lupus due to increased TLR7 signaling by dendritic cells, also develop an age-dependent secondary pathology similar to associated SS. The SS phenotype in TLR8ko mice is manifested by sialadenitis, increased anti-SSA and anti-SSB autoantibody production, immune complex deposition and increased cytokine production in salivary glands, as well as lung inflammation. Moreover, ectopic lymphoid structures characterized by B/T aggregates, formation of high endothelial venules and the presence of dendritic cells are formed in the salivary glands of TLR8ko mice. Interestingly, all these phenotypes are abrogated in double TLR7/8-deficient mice, suggesting that the SS phenotype in TLR8-deficient mice is TLR7-dependent. In addition, evaluation of TLR7 and inflammatory markers in the salivary glands of primary SS patients revealed significantly increased TLR7 expression levels compared to healthy individuals, that were positively correlated to TNF , LT-α , CXCL13 and CXCR5 expression. These findings establish an important role of TLR7 signaling for local and systemic SS disease manifestations, and inhibition of such will likely have therapeutic value., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Wang, Roussel-Queval, Chasson, Hanna Kazazian, Marcadet, Nezos, Sieweke, Mavragani and Alexopoulou.)

In stressed cells, phosphorylation of eukaryotic initiation factor 2α (eIF2α) controls transcriptome-wide changes in mRNA translation and gene expression known as the integrated stress response. We show here that DCs are characterized by high eIF2α phosphorylation, mostly caused by the activation of the ER kinase PERK (EIF2AK3). Despite high p-eIF2α levels, DCs display active protein synthesis and no signs of a chronic integrated stress response. This biochemical specificity prevents translation arrest and expression of the transcription factor ATF4 during ER-stress induction by the subtilase cytotoxin (SubAB). PERK inactivation, increases globally protein synthesis levels and regulates IFN-β expression, while impairing LPS-stimulated DC migration. Although the loss of PERK activity does not impact DC development, the cross talk existing between actin cytoskeleton dynamics; PERK and eIF2α phosphorylation is likely important to adapt DC homeostasis to the variations imposed by the immune contexts., (© 2020 Mendes et al.)

Background: Etiological diagnosis is a key to therapeutic adaptation and improved prognosis, particularly for infections such as endocarditis. In blood culture-negative endocarditis (BCNE), 22% of cases remain undiagnosed despite an updated comprehensive syndromic approach. This prompted us to develop a new diagnostic approach., Methods: Eleven valves from 10 BCNE patients were analyzed using a method that combines human RNA bait-depletion with phi29 DNA polymerase-based multiple displacement amplification and shotgun DNA sequencing. An additional case in which a microbe was serendipitously visualized by immunofluorescence was analyzed using the same method, but after laser capture microdissection., Results: Background DNA prevented any diagnosis in cases analyzed without microdissection because the majority of sequences were contaminants. Moraxella sequences were dramatically enriched in the stained microdissected region of the additional case. A consensus genome sequence of 2.4 Mbp covering more than 94% of the Moraxella osloensis KSH reference genome was reconstructed with 234X average coverage. Several antibiotic-resistance genes were observed. Etiological diagnosis was confirmed using Western blot and specific polymerase chain reaction with sequencing on a different valve sample., Conclusions: Microdissection could be a key to the metagenomic diagnosis of infectious diseases when a microbe is visualized but remains unidentified despite an updated optimal approach. Moraxella osloensis should be tested in blood culture-negative endocarditis., (© The Author(s) 2019. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

The monocyte-derived phagocytes termed LysoDCs are hallmarks of Peyer's patches, where their main function is to sample intestinal microorganisms. Here, we study their differentiation pathways in relation with their sampling, migratory, and T cell-priming abilities. Among four identified LysoDC differentiation stages displaying similar phagocytic activity, one is located in follicles, and the others reside in subepithelial domes (SED), where they proliferate and mature as they get closer to the epithelium. Mature LysoDCs but not macrophages express a gene set in common with conventional dendritic cells and prime naive helper T cells in vitro. At steady state, they do not migrate into naive T cell-enriched interfollicular regions (IFRs), but upon stimulation, they express the chemokine receptor CCR7 and migrate from SED to the IFR periphery, where they strongly interact with proliferative immune cells. Finally, we show that LysoDCs populate human Peyer's patches, strengthening their interest as targets for modulating intestinal immunity., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

In humans, psychological stress has been associated with a higher risk of infectious illness. However, the mechanisms by which the stress pathway interferes with host response to pathogens remain unclear. We demonstrate here a role for the β2-adrenergic receptor (β2-AR), which binds the stress mediators adrenaline and noradrenaline, in modulating host response to mouse cytomegalovirus (MCMV) infection. Mice treated with a β2-AR agonist were more susceptible to MCMV infection. By contrast, β2-AR deficiency resulted in a better clearance of the virus, less tissue damage, and greater resistance to MCMV. Mechanistically, we found a correlation between higher levels of IFN-γ production by liver natural killer (NK) cells and stronger resistance to MCMV. However, the control of NK cell IFN-γ production was not cell intrinsic, revealing a cell-extrinsic downregulation of the antiviral NK cell response by adrenergic neuroendocrine signals. This pathway reduces host immune defense, suggesting that the blockade of the β2-AR signaling could be used to increase resistance to infectious diseases., Competing Interests: Disclosures: The authors declare no competing interests exist., (© 2020 Wieduwild et al.)

Computed tomography is a powerful medical imaging modality for longitudinal studies in cancer to follow neoplasia progression and evaluate anticancer therapies. Here, we report the generation of a photon-counting micro-computed tomography (PC-CT) method based on hybrid pixel detectors with enhanced sensitivity and precision of tumor imaging. We then applied PC-CT for longitudinal imaging in a clinically relevant liver cancer model, the Alb-R26 Met mice, and found a remarkable heterogeneity in the dynamics for tumors at the initiation phases. Instead, the growth curve of evolving tumors exhibited a comparable exponential growth, with a constant doubling time. Furthermore, longitudinal PC-CT imaging in mice treated with a combination of MEK and BCL-XL inhibitors revealed a drastic tumor regression accompanied by a striking remodeling of macrophages in the tumor microenvironment. Thus, PC-CT is a powerful system to detect cancer initiation and progression, and to monitor its evolution during treatment., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Targeting angiogenesis has been and continues to be an attractive therapeutic modality in glioblastoma (GBM) patients. However, GBM rapidly becomes refractory to anti-VEGF therapies. Myeloid cell infiltration is an important determinant of tumor progression. Given that VEGF is a modulator of the innate immune response we sought to analyze the dynamics of this response in a mouse model of GBM undergoing anti-VEGF therapy., Methods: We grafted GL261-DsRed cells in transgenic Thy1-CFP//LysM-EGFP//CD11c-EYFP reporter mice. We combined recurrent spectral two-photon imaging with multiparametric cytometry, immunostaining, and brain clearing to characterize at two critical stages of tumor development (day 21 and day 28 after tumor grafting) the nature and spatial distribution of the innate response in control and bevacizumab-treated mice., Results: We report that at an early stage (21 day), VEGF blockade has a detectable effect on the number of microglial cells but only a mild effect on the number of infiltrating myeloid cells. At a later stage (day 28), the treatment resulted in a specific adjustment of dendritic cell subsets. In treated mice, the number of monocytes and their monocyte-derived dendritic cells (moDC) progeny was increased by approximately twofold compared to untreated mice. In agreement, by in vivo quantitative imaging, we observed that treatment increased the number of LysM-EGFP cells traveling in tumor blood vessels and doubled the densities of both infiltrated LysM-EGFP monocytes and double-labeled EGFP/EYFP moDC. The treatment also led to an increased density of conventional cDCs2 subset together with a decrease of cDCs1 subset, necessary for the development of anti-tumor immunity. Finally, we describe differential spatial cell distributions and two immune cell-traveling routes into the brain. LysM-EGFP cells distributed as a gradient from the meninges towards the tumor whereas CD11c-EYFP/MHCII + cells were located in the basal area of the tumor. Brain clearing also revealed a flow of CD11c-EYFP cells following the corpus callosum., Conclusion: We uncovered new features in the dynamics of innate immune cells in GBM-bearing mice and deciphered precisely the key populations, i.e., DC subsets controlling immune responses, that are affected by VEGF blockade. Since despite differences, human pathogenesis presents similarities with our mouse model, the data provide new insights into the effect of bevacizumab at the cellular level.

Systemic lupus erythematosus (SLE) patients have increased prevalence of metabolic syndrome but the underlying mechanisms are unknown. Toll-like receptor 7 (TLR7) that detects single stranded-RNA plays a key role in antimicrobial host defense and also contributes to the initiation and progression of SLE both in mice and humans. Here, we report the implication of TLR7 signaling in high fat diet (HFD)-induced metabolic syndrome and exacerbation of lupus autoimmunity in TLR8-deficient (TLR8ko) mice, which develop spontaneous lupus-like disease due to increased TLR7 signaling by dendritic cells (DCs). The aggravated SLE pathogenesis in HFD-fed TLR8ko mice was characterized by increased overall immune activation, anti-DNA autoantibody production, and IgG/IgM glomerular deposition that were coupled with increased kidney histopathology. Moreover, upon HFD TLR8ko mice developed metabolic abnormalities, including liver inflammation. In contrast, upon HFD TLR7/8ko mice did not develop SLE and both TLR7ko and TLR7/8ko mice were fully protected from metabolic abnormalities, including body weight gain, insulin resistance, and liver inflammation. Interestingly, HFD led to an increase of TLR7 expression in WT mice, that was coupled with increased TNF production by DCs, and this phenotype was more profound in TLR8ko mice. Our study uncovers the implication of TLR7 signaling in the interconnection of SLE and metabolic abnormalities, indicating that TLR7 might be a novel approach as a tailored therapy in SLE and metabolic diseases.

In the bone marrow, CXCL12 and IL-7 are essential for B cell differentiation, whereas hematopoietic stem cell (HSC) maintenance requires SCF and CXCL12. Peri-sinusoidal stromal (PSS) cells are the main source of IL-7, but their characterization as a pro-B cell niche remains limited. Here, we characterize pro-B cell supporting stromal cells and decipher the interaction network allowing pro-B cell retention. Preferential contacts are found between pro-B cells and PSS cells, which homogeneously express HSC and B cell niche genes. Furthermore, pro-B cells are frequently located in the vicinity of HSCs in the same niche. Using an interactome bioinformatics pipeline, we identify Nidogen-1 as essential for pro-B cell retention in the peri-sinusoidal niche as confirmed in Nidogen-1 -/- mice. Finally, human pro-B cells and hematopoietic progenitors are observed close to similar IL-7 + stromal cells. Thus, a multispecific niche exists in mouse and human supporting both early progenitors and committed hematopoietic lineages., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

Controlling the balance between immunity and immunopathology is crucial for host resistance to pathogens. After infection, activation of the hypothalamic-pituitary-adrenal (HPA) axis leads to the production of glucocorticoids. However, the pleiotropic effects of these steroid hormones make it difficult to delineate their precise role(s) in vivo. Here we found that the regulation of natural killer (NK) cell function by the glucocorticoid receptor (GR) was required for host survival after infection with mouse cytomegalovirus (MCMV). Mechanistically, endogenous glucocorticoids produced shortly after infection induced selective and tissue-specific expression of the checkpoint receptor PD-1 on NK cells. This glucocorticoid-PD-1 pathway limited production of the cytokine IFN-γ by spleen NK cells, which prevented immunopathology. Notably, this regulation did not compromise viral clearance. Thus, the fine tuning of NK cell functions by the HPA axis preserved tissue integrity without impairing pathogen elimination, which reveals a novel aspect of neuroimmune regulation.

Like other tumors, aggressive soft tissue sarcomas (STS) use glycolysis rather than mitochondrial oxidative phosphorylation (OXPHOS) for growth. Given the importance of the cofactor coenzyme A (CoA) in energy metabolism, we investigated the impact of Vnn1 pantetheinase-an enzyme that degrades pantetheine into pantothenate (vitamin B5, the CoA biosynthetic precursor) and cysyteamine-on tumor growth. Using two models, we show that Vnn1 + STS remain differentiated and grow slowly, and that in patients a detectable level of VNN1 expression in STS is associated with an improved prognosis. Increasing pantetheinase activity in aggressive tumors limits their growth. Using combined approaches, we demonstrate that Vnn1 permits restoration of CoA pools, thereby maintaining OXPHOS. The simultaneous production of cysteamine limits glycolysis and release of lactate, resulting in a partial inhibition of STS growth in vitro and in vivo. We propose that the Warburg effect observed in aggressive STS is reversed by induction of Vnn1 pantetheinase and the rewiring of cellular energy metabolism by its products., Competing Interests: The authors declare that they have no conflict of interest.

Endoplasmic reticulum (ER) stress triggers or amplifies inflammatory signals and cytokine production in immune cells. Upon the resolution of ER stress, the inducible phosphatase 1 cofactor GADD34 promotes the dephosphorylation of the initiation factor eIF2α, thereby enabling protein translation to resume. Several aminoguanidine compounds, such as guanabenz, perturb the eIF2α phosphorylation-dephosphorylation cycle and protect different cell or tissue types from protein misfolding and degeneration. We investigated how pharmacological interference with the eIF2α pathway could be beneficial to treat autoinflammatory diseases dependent on proinflammatory cytokines and type I interferons (IFNs), the production of which is regulated by GADD34 in dendritic cells (DCs). In mouse and human DCs and B cells, guanabenz prevented the activation of Toll-like receptor 9 (TLR9) by CpG oligodeoxynucleotides or DNA-immunoglobulin complexes in endosomes. In vivo, guanabenz protected mice from CpG oligonucleotide-dependent cytokine shock and decreased autoimmune symptom severity in a chemically induced model of systemic lupus erythematosus. However, we found that guanabenz exerted its inhibitory effect independently of GADD34 activity on eIF2α and instead decreased the abundance of CH25H, a cholesterol hydroxylase linked to antiviral immunity. Our results therefore suggest that guanabenz and similar compounds could be used to treat type I IFN-dependent pathologies and that CH25H could be a therapeutic target to control these diseases., (Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

The spleen plays an important role in protective immunity to bloodborne pathogens. Macrophages and dendritic cells (DCs) in the spleen marginal zone capture microbial antigens to trigger adaptive immune responses. Marginal zone macrophages (MZMs) can also act as a replicative niche for intracellular pathogens, providing a platform for mounting the immune response. Here, we describe a role for RANK in the coordinated function of antigen-presenting cells in the spleen marginal zone and triggering anti-viral immunity. Targeted deletion of RANK results in the selective loss of CD169 + MZMs, which provide a niche for viral replication, while RANK signaling in DCs promotes the recruitment and activation of anti-viral memory CD8 T cells. These studies reveal a role for the RANKL/RANK signaling axis in the orchestration of protective immune responses in the spleen marginal zone that has important implications for the host response to viral infection and induction of acquired immunity., (Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.)

Multi-organ failure in response to uncontrolled microbial infection is characterized by low blood pressure accompanied by a systemic over-inflammation state, caused by massive pro-inflammatory cytokines release and liver damage. Recently, the integrated stress response (ISR), characterized by eukaryotic translation initiation factor 2α (eIF2α) phosphorylation, was involved with controlling apoptosis in stressed hepatocytes and associated with poor survival to endotoxin challenge. Lipopolysaccharide (LPS) alone is able to induce the ISR in hepatocytes and can trigger massive liver damage along with tumor necrosis factor-alpha (TNF-α) expression. Consequently, drugs interfering with eIF2α phosphorylation may represent potential candidates for the treatment of such pathologies. We, therefore, used Guanabenz (GBZ), a small compound with enhancing eIF2α phosphorylation activity to evaluate its effect on bacterial LPS sensing and endotoxemia. GBZ is confirmed here to have an anti-inflammatory activity by increasing in vitro interleukin-10 (IL-10) production by LPS-stimulated dendritic cells. We further show that in the d-galactosamine (d-galN)/LPS-dependent lethality model, intraperitoneal injection of GBZ promoted mice survival, prevented liver damage, increased IL-10 levels, and inhibited TNF-α production. GBZ and its derivatives could therefore represent an interesting pharmacological solution to control systemic inflammation and associated acute liver failure.

Background and Aims: Pretreatment with clofibrate, a peroxisome proliferator-activated receptor alpha (PPARa) agonist, protects mice from acetaminophen (APAP) injury. Protection is not due to alterations in APAP metabolism and is dependent on PPARa expression. Gene array analysis revealed that mice receiving clofibrate have enhanced hepatic Vanin-1 (Vnn1) gene expression, a response that is also PPARa dependent., Methods: We examined the role of Vnn1 by comparing the responses of Vnn1 knockout and wild-type mice following APAP hepatotoxicity. APAP metabolism, hepatotoxicity, and compensatory hepatocyte proliferation and immune responses were assessed., Results: Vnn1 knockout mice are more susceptible to APAP hepatotoxicity despite no differences in hepatic glutathione content, gene expression of APAP metabolizing enzymes, or hepatic capacity to bioactivate or detoxify APAP ex vivo. Together, these data strongly suggest that the susceptibility of Vnn1 knockout mice is not due to differences in APAP metabolism. Immunochemistry revealed a lack of proliferating cell nuclear antigen-positive hepatocytes and F4/80-positive macrophages in and around areas of centrilobular necrosis in APAP-treated Vnn1 knockouts. Hepatic gene induction of pro-inflammatory cytokines was either significantly reduced or completely blunted in these mice. This was correlated with a reduction in early recruitment of cells positive for granulocyte differentiation antigen 1 or integrin alpha M. Heightened toxicity was also observed in CCl4 and ConA hepatitis models in the absence of Vnn1., Conclusions: These results indicate that mice lacking Vnn1 have deficiencies in compensatory repair and immune responses following toxic APAP exposure and that these mechanisms may contribute to the enhanced hepatotoxicity seen., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Tissue pantetheinase, encoded by the VNN1 gene, regulates response to stress, and previous studies have shown that VNN genes contribute to the susceptibility to malaria. Herein, we evaluated the role of pantetheinase on erythrocyte homeostasis and on the development of malaria in patients and in a new mouse model of pantetheinase insufficiency. Patients with cerebral malaria have significantly reduced levels of serum pantetheinase activity (PA). In mouse, we show that a reduction in serum PA predisposes to severe malaria, including cerebral malaria and severe anemia. Therefore, scoring pantetheinase in serum may serve as a severity marker in malaria infection. This disease triggers an acute stress in erythrocytes, which enhances cytoadherence and hemolysis. We speculated that serum pantetheinase might contribute to erythrocyte resistance to stress under homeostatic conditions. We show that mutant mice with a reduced serum PA are anemic and prone to phenylhydrazine-induced anemia. A cytofluorometric and spectroscopic analysis documented an increased frequency of erythrocytes with an autofluorescent aging phenotype. This is associated with an enhanced oxidative stress and shear stress-induced hemolysis. Red blood cell transfer and bone marrow chimera experiments show that the aging phenotype is not cell intrinsic but conferred by the environment, leading to a shortening of red blood cell half-life. Therefore, serum pantetheinase level regulates erythrocyte life span and modulates the risk of developing complicated malaria., (Copyright © 2015 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

In mice, plasmacytoid dendritic cells (pDC) and natural killer (NK) cells both contribute to resistance to systemic infections with herpes viruses including mouse Cytomegalovirus (MCMV). pDCs are the major source of type I IFN (IFN-I) during MCMV infection. This response requires pDC-intrinsic MyD88-dependent signaling by Toll-Like Receptors 7 and 9. Provided that they express appropriate recognition receptors such as Ly49H, NK cells can directly sense and kill MCMV-infected cells. The loss of any one of these responses increases susceptibility to infection. However, the relative importance of these antiviral immune responses and how they are related remain unclear. In humans, while IFN-I responses are essential, MyD88 is dispensable for antiviral immunity. Hence, a higher redundancy has been proposed in the mechanisms promoting protective immune responses against systemic infections by herpes viruses during natural infections in humans. It has been assumed, but not proven, that mice fail to mount protective MyD88-independent IFN-I responses. In humans, the mechanism that compensates MyD88 deficiency has not been elucidated. To address these issues, we compared resistance to MCMV infection and immune responses between mouse strains deficient for MyD88, the IFN-I receptor and/or Ly49H. We show that selective depletion of pDC or genetic deficiencies for MyD88 or TLR9 drastically decreased production of IFN-I, but not the protective antiviral responses. Moreover, MyD88, but not IFN-I receptor, deficiency could largely be compensated by Ly49H-mediated antiviral NK cell responses. Thus, contrary to the current dogma but consistent with the situation in humans, we conclude that, in mice, in our experimental settings, MyD88 is redundant for IFN-I responses and overall defense against a systemic herpes virus infection. Moreover, we identified direct NK cell sensing of infected cells as one mechanism able to compensate for MyD88 deficiency in mice. Similar mechanisms likely contribute to protect MyD88- or IRAK4-deficient patients from viral infections.

Peyer's patches (PPs) are primary inductive sites of mucosal immunity. Defining PP mononuclear phagocyte system (MPS) is thus crucial to understand the initiation of mucosal immune response. We provide a comprehensive analysis of the phenotype, distribution, ontogeny, lifespan, function, and transcriptional profile of PP MPS. We show that monocytes give rise to macrophages and to lysozyme-expressing dendritic cells (LysoDCs), which are both involved in particulate antigen uptake, display strong innate antiviral and antibacterial gene signatures, and, upon TLR7 stimulation, secrete IL-6 and TNF, but neither IL-10 nor IFNγ. However, unlike macrophages, LysoDCs display a rapid renewal rate, strongly express genes of the MHCII presentation pathway, and prime naive helper T cells for IFNγ production. Our results show that monocytes differentiate locally into LysoDCs and macrophages, which display distinct features from their adjacent villus counterparts., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

CD8 T cells contribute to long-term protection against Listeria monocytogenes infection by differentiating into memory T cells. These rapidly respond to antigen or inflammation upon secondary infection. In this study we used CD8 T cells from OT1 mice and CD4 T cells from OT2 mice expressing a fluorescent chimeric granzyme (GZMB-Tom) protein to monitor the primary response to infection with ovalbumin-expressing L. monocytogenes (Lm-OVA). We show that, unlike poorly responding CD4 T cells, CD8 T cells readily proliferated and expressed high levels of GZMB-Tom as early as 2 days after infection. FACS analysis showed GZMB-Tom expression in undivided CD8 T cells, with its level increasing over one to four divisions. OT1 T cells were visualized in the T-cell zone by confocal microscopy. This showed GZMB-Tom-containing granules oriented towards MHCII-positive cells. Twenty hours later, most OT1 T cells had divided but their level of GZMB-Tom expression was reduced. Recently divided OT1 cells failed to express GZMB-Tom. Fourteen hours after secondary infection, GZMB-Tom was re-expressed in memory OT1 T cells responding either to Lm-OVA or L. monocytogenes. Differences in the activation phenotype and in the splenic distribution of OT1 T cells were observed, depending on the challenge. Notably, OTI T cells with polarized granules were only observed after challenge with cognate antigen. This work showed that the GZMB-Tom knock-in mice in which GZMB-Tom faithfully reproduced GZMB expression, provide useful tools to dissect mechanisms leading to the development of anti-bacterial effector and memory CD8 T cells and reactivation of the memory response to cognate antigen or inflammatory signals., (© 2014 INSERM and CNRS.)

Cervical lymph nodes (CLN) are the first lymph nodes encountered by material taking the oral route. To study their role in orally acquired infections, we analyzed 307 patients of up to 14 years treated in the university clinic of Skopje, Macedonia, for brucellosis, a zoonotic bacterial disease frequently acquired by ingestion of contaminated dairy products. From these children, 36% had lymphadenopathy. Among orally infected children, lymphadenopathy with CLN being the only lymph nodes affected was significantly more frequent as compared to those infected by contact with animals (83% vs. 63%), suggesting a possible involvement of CLN during orally acquired human brucellosis. Using a murine model where bacteria are delivered into the oral cavity, we show that Brucella quickly and selectively colonize the CLN where they proliferate and persist over long periods of time for up to 50 days post-infection. A similar efficient though less specific drainage to CLN was found for Brucella, Salmonella typhimurium and fluorescent microspheres delivered by gavage, a pathway likely representing a mixed infection mode of intragastric and oral infection, suggesting a central pathway of drained material. Microspheres as well as bacteria drained to CLN predominately reside in cells expressing CD68 and no or low levels of CD11c. Even though no systemic response could be detected, Brucella induced a locally restricted inflammatory reaction with increased expression levels of interferon γ, interleukin (IL)-6, IL-12, granzyme B and a delayed induction of Nos2. Inflammation led to pronounced lymphadenopathy, infiltration of macrophages/monocytes expressing high levels of major histocompatibility complex II and to formation of epitheloid granulomas. Together, these results highlight the role of CLN in oral infections as both, an initial and efficient trap for bacterial invaders and as possible reservoir for chronic pathogens. They likewise cast a new light on the significance of oral routes for means of vaccination.

Tumors with reduced expression of MHC class I (MHC-I) molecules may be unrecognized by tumor antigen-specific CD8 + T cells and thus constitute a challenge for cancer immunotherapy. Here we monitored development of autochthonous melanomas in TiRP mice that develop tumors expressing a known tumor antigen as well as a red fluorescent protein (RFP) reporter knock in gene. The latter permits non-invasive monitoring of tumor growth by biofluorescence. One developing melanoma was deficient in cell surface expression of MHC-I, but MHC-I expression could be rescued by exposure of these cells to IFNγ. We show that CD8 + T cells specific for tumor antigen/MHC-I were efficient at inducing regression of the MHC-I-deficient melanoma, provided that the T cells were endowed with properties permitting their migration into the tumor and their efficient production of IFNγ. This was the case for CD8 + T cells transfected to express an active form of STAT5 (STAT5CA). The amount of IFNγ produced ex vivo from T cells present in tumors after adoptive transfer of the CD8 + T cells was correlated with an increase in surface expression of MHC-I molecules by the tumor cells. We also show that these CD8 + T cells expressed PD-1 and upregulated its ligand PDL-1 on melanoma cells within the tumor. Despite upregulation of this immunosuppressive pathway, efficient IFNγ production in the melanoma microenvironment was found associated with resistance of STAT5CA-expressing CD8 + T cells to inhibition both by PD-1/PDL-1 engagement and by TGFβ1, two main immune regulatory mechanisms hampering the efficiency of immunotherapy in patients.

It has recently been demonstrated that memory B cells can reenter and reengage germinal center (GC) reactions, opening the possibility that multi-hit lymphomagenesis gradually occurs throughout life during successive immunological challenges. Here, we investigated this scenario in follicular lymphoma (FL), an indolent GC-derived malignancy. We developed a mouse model that recapitulates the FL hallmark t(14;18) translocation, which results in constitutive activation of antiapoptotic protein B cell lymphoma 2 (BCL2) in a subset of B cells, and applied a combination of molecular and immunofluorescence approaches to track normal and t(14;18)(+) memory B cells in human and BCL2-overexpressing B cells in murine lymphoid tissues. BCL2-overexpressing B cells required multiple GC transits before acquiring FL-associated developmental arrest and presenting as GC B cells with constitutive activation-induced cytidine deaminase (AID) mutator activity. Moreover, multiple reentries into the GC were necessary for the progression to advanced precursor stages of FL. Together, our results demonstrate that protracted subversion of immune dynamics contributes to early dissemination and progression of t(14;18)(+) precursors and shapes the systemic presentation of FL patients.

The transcription factor NF-κB is central to inflammatory signaling and activation of innate and adaptive immune responses. Activation of the NF-κB pathway is tightly controlled by several negative feedback mechanisms, including A20, an ubiquitin-modifying enzyme encoded by the tnfaip3 gene. Mice with selective deletion of A20 in myeloid, dendritic, or B cells recapitulate some human inflammatory pathology. As we observed high expression of A20 transcripts in dysfunctional CD8 T cells in an autochthonous melanoma, we analyzed the role of A20 in regulation of CD8 T-cell functions, using mice in which A20 was selectively deleted in mature conventional T cells. These mice developed lymphadenopathy and some organ infiltration by T cells but no splenomegaly and no detectable pathology. A20-deleted CD8 T cells had increased sensitivity to antigen stimulation with production of large amounts of IL-2 and IFNγ, correlated with sustained nuclear expression of NF-κB components reticuloendotheliosis oncogene c-Rel and p65. Overexpression of A20 by retroviral transduction of CD8 T cells dampened their intratumor accumulation and antitumor activity. In contrast, relief from the A20 brake in NF-κB activation in adoptively transferred antitumor CD8 T cells led to improved control of melanoma growth. Tumor-infiltrating A20-deleted CD8 T cells had enhanced production of IFNγ and TNFα and reduced expression of the inhibitory receptor programmed cell death 1. As manipulation of A20 expression in CD8 T cells did not result in pathologic manifestations in the mice, we propose it as a candidate to be targeted to increase antitumor efficiency of adoptive T-cell immunotherapy.

Follicular lymphoma (FL) is a B-cell neoplasm resulting from the transformation of germinal center (GC) B cells. Although t(14;18) and ectopic B-cell lymphoma 2 (BCL2) expression constitute the genetic hallmark of FL, t(14;18)(pos) B cells bearing genotypic and phenotypic features of FL cells can be found in the blood of most healthy individuals. Nevertheless, the localization of these FL-like cells (FLLCs) in nonmalignant GC-rich tissues and the functional consequences of BCL2 overexpression have not been evaluated thus far. Among 85 reactive lymph node (RLN) samples, 14% were found to contain high levels of t(14;18) by quantitative polymerase chain reaction. In t(14;18)(hi) RLNs, CD20(pos)BCL2(pos)CD10(pos) FLLCs consistently accumulated within the GC, essentially as nonproliferative CXCR4(neg) centrocytes. Moreover, they displayed a reduced response to proliferative stimuli in vitro. Altogether, our findings provide new insights into in situ FLLC functional properties and suggest that these cells have not acquired the ultimate genetic events leading to FL transformation., (© 2014 by The American Society of Hematology.)

MYC is a potent oncogene involved in ∼70% of human cancers, inducing tumorigenesis with high penetrance and short latency in experimental transgenic models. Accordingly, MYC is recognized as a major driver of T-cell acute lymphoblastic leukemia (T-ALL) in human and zebrafish/mouse models, and uncovering the context by which MYC-mediated malignant transformation initiates and develops remains a considerable challenge. Because MYC is a very complex oncogene, highly dependent on the microenvironment and cell-intrinsic context, we generated transgenic mice (tgMyc(spo)) in which ectopic Myc activation occurs sporadically (<10(-6) thymocytes) within otherwise normal thymic environment, thereby mimicking the unicellular context in which oncogenic alterations initiate human tumors. We show that while Myc(+) clones in tgMyc(spo) mice develop and initially proliferate in thymus and the periphery, no tumor or clonal expansion progress in aging mice (n = 130), suggesting an unexpectedly low ability of Myc to initiate efficient tumorigenesis. Furthermore, to determine the relevance of this observation in human pathogenesis we analyzed a human T-ALL case at diagnosis and relapse using the molecular stigmata of V(D)J recombination as markers of malignant progression; we similarly demonstrate that despite the occurrence of TAL1 and MYC translocations in early thymocyte ontogeny, subsequent oncogenic alterations were required to drive oncogenesis. Altogether, our data suggest that although central to T-ALL, MYC overexpression per se is inefficient in triggering the cascade of events leading to malignant transformation., (Copyright © 2013 Wiley Periodicals, Inc.)

The membrane-bound Vanin-1 pantetheinase regulates tissue adaptation to stress. We investigated Vnn1 expression and its regulation in liver. Vnn1 is expressed by centrolobular hepatocytes. Using novel tools, we identify a soluble form of Vnn1 in mouse and human serum and show the contribution of a cysteine to its catalytic activity. We show that liver contributes to Vanin-1 secretion in serum and that PPARalpha is a limiting factor in serum Vnn1 production. Functional PPRE sites are identified in the Vnn1 promoter. These results indicate that serum Vnn1 might be a reliable reporter of PPARalpha activity in liver., (Copyright © 2013 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)

Galectin-1 (GAL1) is an S-type lectin with multiple functions, including the control of B cell homeostasis. GAL1 expression was reported to be under the control of the plasma cell master regulator BLIMP-1. GAL1 was detected at the protein level in LPS-stimulated B cells and was shown to promote Ig secretion in vitro. However, the pattern of GAL1 expression and function of GAL1 in B cells in vivo are still unclear. In this study, we show that, among B cells, GAL1 is only expressed by differentiating plasma cells following T-dependent or T-independent immunization. Using GAL1-deficient mice we demonstrate that GAL1 expression is required for the maintenance of Ag-specific Ig titers and Ab-secreting cell numbers. Using an in vitro differentiation assay we find that GAL1-deficient plasmablasts can develop normally but die rapidly, through caspase 8 activation, under serum starvation-induced death conditions. TUNEL assays show that in vivo-generated GAL1-deficient plasma cells exhibit an increased sensitivity to apoptosis. Taken together, our data indicate that endogenous GAL1 supports plasma cell survival and participates in the regulation of the humoral immune response.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition due to the association of an infectious agent with lymphocyte cytotoxicity defects, either of congenital genetic origin in children or presumably acquired in adults. In HLH patients, an excess of lymphocyte or macrophage cytokines, such as IFN-γ and TNFα is present in serum. In animal models of the disease, IFN-γ and TNF-α have been shown to play a central pathogenic role. In humans, unusually high concentrations of IL-18, an inducer of IFN-γ, and TNF-α have been reported, and are associated with an imbalance between IL-18 and its natural inhibitor IL-18 binding protein (IL-18BP) resulting in an excess of free IL-18. Here we studied whether IL-18BP could reduce disease severity in an animal model of HLH. Mouse cytomegalovirus infection in perforin-1 knock-out mice induced a lethal condition similar to human HLH characterized by cytopenia with marked inflammatory lesions in the liver and spleen as well as the presence of hemophagocytosis in bone marrow. IL-18BP treatment decreased hemophagocytosis and reversed liver as well as spleen damage. IL-18BP treatment also reduced both IFN-γ and TNF-α production by CD8(+) T and NK cells, as well as Fas ligand expression on NK cell surface. These data suggest that IL-18BP is beneficial in an animal model of HLH and in combination with anti-infectious therapy may be a promising strategy to treat HLH patients.

In response to inflammatory stimulation, dendritic cells (DCs) have a remarkable pattern of differentiation that exhibits specific mechanisms to control the immune response. Here we show that in response to polyriboinosinic:polyribocytidylic acid (pI:C), DCs mount a specific integrated stress response during which the transcription factor ATF4 and the growth arrest and DNA damage-inducible protein 34 (GADD34/Ppp1r15a), a phosphatase 1 (PP1) cofactor, are expressed. In agreement with increased GADD34 levels, an extensive dephosphorylation of the translation initiation factor eIF2α was observed during DC activation. Unexpectedly, although DCs display an unusual resistance to protein synthesis inhibition induced in response to cytosolic dsRNA, GADD34 expression did not have a major impact on protein synthesis. GADD34, however, was shown to be required for normal cytokine production both in vitro and in vivo. These observations have important implications in linking further pathogen detection with the integrated stress response pathways.

Toll-like receptor (TLR)-dependent pathways control the activation of various immune cells and the production of cytokines and chemokines that are important in innate immune control of viruses, including mouse cytomegalovirus (MCMV). Here we report that upon MCMV infection wild-type and TLR7(-/-) male mice were more resistant than their female counterparts, while TLR9(-/-) male and female mice showed similar susceptibility. Interestingly, 36 h upon MCMV infection TLR9 mRNA expression was higher in male than in female mouse spleens. MCMV infection led to stronger reduction of marginal zone (MZ) B cells, and higher infiltration of plasmacytoid dendritic cells and neutrophils in wild-type male than female mice, while no such sex differences were observed in TLR9(-/-) mice. In accordance, the serum levels of KC and MIP-2, major neutrophil chemoattractants, were higher in wild-type, but not in TLR9(-/-), male versus female mice. Wild-type MCMV-infected female mice showed more severe liver inflammation, necrosis and steatosis compared to infected male mice. Our data demonstrate sex differences in susceptibility to MCMV infection, accompanied by a lower activation of the innate immune system in female mice, and can be attributed, at least in a certain degree, to the lower expression of TLR9 in female than male mice.

We compared gene expression signatures of aggressive amelanotic (Amela) melanomas with those of slowly growing pigmented melanomas (Mela), identifying pathways potentially responsible for the aggressive Amela phenotype. Both tumors develop in mice upon conditional deletion in melanocytes of Ink4a/Arf tumor suppressor genes with concomitant expression of oncogene H-Ras(G12V) and a known tumor antigen. We previously showed that only the aggressive Amela tumors were highly infiltrated by leukocytes concomitant with local and systemic inflammation. We report that Amela tumors present a pattern of de-differentiation with reduced expression of genes involved in pigmentation. This correlates with reduced and enhanced expression, respectively, of microphthalmia-associated (Mitf) and Pou3f2/Brn-2 transcription factors. The reduced expression of Mitf-controlled melanocyte differentiation antigens also observed in some human cutaneous melanoma has important implications for immunotherapy protocols that generally target such antigens. Induced Amela tumors also express Epithelial-Mesenchymal-Transition (EMT)-like and TGFβ-pathway signatures. These are correlated with constitutive Smad3 signaling in Amela tumors and melanoma cell lines. Signatures of infiltrating leukocytes and some chemokines such as chemotactic cytokine ligand 2 (Ccl2) that contribute to leukocyte recruitment further characterize Amela tumors. Inhibition of the mitogen-activated protein kinase (MAPK) activation pathway in Amela tumor lines leads to reduced expression of EMT hallmark genes and inhibits both proinflammatory cytokine Ccl2 gene expression and Ccl2 production by the melanoma cells. These results indicate a link between EMT-like processes and alterations of immune functions, both being controlled by the MAPK pathway. They further suggest that targeting the MAPK pathway within tumor cells will impact tumor-intrinsic oncogenic properties as well as the nature of the tumor microenvironment.

In the bone marrow (BM), stromal cells constitute a supportive tissue indispensable for the generation of pro-B/pre-BI, pre-BII, and immature B lymphocytes. IL-7-producing stromal cells constitute a cellular niche for pro-B/pre-BI cells, but no specific stromal cell microenvironment was identified for pre-BII cells expressing a functional pre-B cell receptor (pre-BCR). However expression of the pre-BCR represents a crucial checkpoint during B-cell development. We recently demonstrated that the stromal cell derived-galectin1 (GAL1) is a ligand for the pre-BCR, involved in the proliferation and differentiation of normal mouse pre-BII cells. Here we show that nonhematopoietic osteoblasts and reticular cells in the BM express GAL1. We observed that pre-BII cells, unlike the other B-cell subsets, were specifically localized in close contact with GAL1(+) reticular cells. We also determined that IL-7(+) and GAL1(+) cells represent 2 distinct mesenchymal populations with different BM localization. These results demonstrate the existence of a pre-BII specific stromal cell niche and indicate that early B cells move from IL-7(+) to GAL1(+) supportive BM niches during their development.

The oxidative burst produced by the NADPH oxidase (Phox) is an essential weapon used by host cells to eradicate engulfed pathogens. In Salmonella typhimurium, oxidative stress resistance has been previously proposed to be mediated by the pathogenicity island 2 type III secretion system (T3SS-2), periplasmic superoxide dismutases and cytoplasmic catalases/peroxidases. Here, we fused an OxyR-dependent promoter to the gfp to build the ahpC-gfp transcriptional fusion. This reporter was used to monitor hydrogen peroxide levels as sensed by Salmonella during the course of an infection. We showed that the expression of this fusion was under the exclusive control of reactive oxygen species produced by the host. The ahpC-gfp expression was noticeably modified in the absence of bacterial periplasmic superoxide dismutases or cytoplasmic catalases/peroxidases. Surprisingly, inactivation of the T3SS-2 had no effect on the ahpC-gfp expression. All together, these results led to a model in which Salmonella resistance relies on its arsenal of detoxifying enzymes to cope with Phox-mediated oxidative stress., (© 2011 Blackwell Publishing Ltd.)

Migration of dendritic cells (DC) from the tumor environment to the T cell cortex in tumor-draining lymph nodes (TDLN) is essential for priming naïve T lymphocytes (TL) to tumor antigen (Ag). We used a mouse model of induced melanoma in which similar oncogenic events generate two phenotypically distinct melanomas to study the influence of tumor-associated inflammation on secondary lymphoid organ (SLO) organization. One tumor promotes inflammatory cytokines, leading to mobilization of immature myeloid cells (iMC) to the tumor and SLO; the other does not. We report that inflammatory tumors induced alterations of the stromal cell network of SLO, profoundly altering the distribution of TL and the capacity of skin-derived DC and TL to migrate or home to TDLN. These defects, which did not require tumor invasion, correlated with loss of fibroblastic reticular cells in T cell zones and in impaired production of CCL21. Infiltrating iMC accumulated in the TDLN medulla and the splenic red pulp. We propose that impaired function of the stromal cell network during chronic inflammation induced by some tumors renders spleens non-receptive to TL and TDLN non-receptive to TL and migratory DC, while the entry of iMC into these perturbed SLO is enhanced. This could constitute a mechanism by which inflammatory tumors escape immune control. If our results apply to inflammatory tumors in general, the demonstration that SLO are poorly receptive to CCR7-dependent migration of skin-derived DC and naïve TL may constitute an obstacle for proposed vaccination or adoptive TL therapies of their hosts.