Clonal replacement sustains long-lived germinal centers primed by respiratory viruses.

Germinal centers (GCs) form in secondary lymphoid organs in response to infection and immunization and are the source of affinity-matured B cells. The duration of GC reactions spans a wide range, and long-lasting GCs (LLGCs) are potentially a source of highly mutated B cells. We show that rather than consisting of continuously evolving B cell clones, LLGCs elicited by influenza virus or SARS-CoV-2 infection in mice are sustained by progressive replacement of founder clones by naive-derived invader B cells that do not detectably bind viral antigens. Rare founder clones that resist replacement for long periods are enriched in clones with heavily mutated immunoglobulins, including some with very high affinity for antigen, that can be recalled by boosting. Our findings reveal underappreciated aspects of the biology of LLGCs generated by respiratory virus infection and identify clonal replacement as a potential constraint on the development of highly mutated antibodies within these structures.

Stepwise chromatin and transcriptional acquisition of an intraepithelial lymphocyte program.

Mesenteric lymph node (mLN) T cells undergo tissue adaptation upon migrating to intestinal lamina propria and epithelium, ensuring appropriate balance between tolerance and resistance. By combining mouse genetics with single-cell and chromatin analyses, we uncovered the molecular imprinting of gut epithelium on T cells. Transcriptionally, conventional and regulatory (Treg) CD4+ T cells from mLN, lamina propria and intestinal epithelium segregate based on the gut layer they occupy; trajectory analysis suggests a stepwise loss of CD4 programming and acquisition of an intraepithelial profile. Treg cell fate mapping coupled with RNA sequencing and assay for transposase-accessible chromatin followed by sequencing revealed that the Treg cell program shuts down before an intraepithelial program becomes fully accessible at the epithelium. Ablation of CD4-lineage-defining transcription factor ThPOK results in premature acquisition of an intraepithelial lymphocyte profile by mLN Treg cells, partially recapitulating epithelium imprinting. Thus, coordinated replacement of the circulating lymphocyte program with site-specific transcriptional and chromatin changes is necessary for tissue imprinting.

Newly recruited intraepithelial Ly6A+CCR9+CD4+ T cells protect against enteric viral infection.

The intestinal epithelium comprises the body's largest surface exposed to viruses. Additionally, the gut epithelium hosts a large population of intraepithelial T lymphocytes, or IELs, although their role in resistance against viral infections remains elusive. By fate-mapping T cells recruited to the murine intestine, we observed an accumulation of newly recruited CD4+ T cells after infection with murine norovirus CR6 and adenovirus type-2 (AdV), but not reovirus. CR6- and AdV-recruited intraepithelial CD4+ T cells co-expressed Ly6A and chemokine receptor CCR9, exhibited T helper 1 and cytotoxic profiles, and conferred protection against AdV in vivo and in an organoid model in an IFN-γ-dependent manner. Ablation of the T cell receptor (TCR) or the transcription factor ThPOK in CD4+ T cells prior to AdV infection prevented viral control, while TCR ablation during infection did not impact viral clearance. These results uncover a protective role for intraepithelial Ly6A+CCR9+CD4+ T cells against enteric adenovirus.

T Cell Receptor Is Required for Differentiation, but Not Maintenance, of Intestinal CD4+ Intraepithelial Lymphocytes.

The gut epithelium is populated by intraepithelial lymphocytes (IELs), a heterogeneous T cell population with cytotoxic and regulatory properties, which can be acquired at the epithelial layer. However, the role of T cell receptor (TCR) in this process remains unclear. Single-cell transcriptomic analyses revealed distinct clonal expansions between cell states, with CD4+CD8αα+ IELs being one of the least diverse populations. Conditional deletion of TCR on differentiating CD4+ T cells or of major histocompatibility complex (MHC) class II on intestinal epithelial cells prevented CD4+CD8αα+ IEL differentiation. However, TCR ablation on differentiated CD4+CD8αα+ IELs or long-term cognate antigen withdraw did not affect their maintenance. TCR re-engagement of antigen-specific CD4+CD8αα+ IELs by Listeria monocytogenes did not alter their state but correlated with reduced bacterial invasion. Thus, local antigen recognition is an essential signal for differentiation of CD4+ T cells at the epithelium, yet differentiated IELs are able to preserve an effector program in the absence of TCR signaling.

Tunable dynamics of B cell selection in gut germinal centres.

Germinal centres, the structures in which B cells evolve to produce antibodies with high affinity for various antigens, usually form transiently in lymphoid organs in response to infection or immunization. In lymphoid organs associated with the gut, however, germinal centres are chronically present. These gut-associated germinal centres can support targeted antibody responses to gut infections and immunization1. But whether B cell selection and antibody affinity maturation take place in the face of the chronic and diverse antigenic stimulation characteristic of these structures under steady state is less clear2-8. Here, by combining multicolour 'Brainbow' cell-fate mapping and sequencing of immunoglobulin genes from single cells, we find that 5-10% of gut-associated germinal centres from specific-pathogen-free (SPF) mice contain highly dominant 'winner' B cell clones at steady state, despite rapid turnover of germinal-centre B cells. Monoclonal antibodies derived from these clones show increased binding, compared with their unmutated precursors, to commensal bacteria, consistent with antigen-driven selection. The frequency of highly selected gut-associated germinal centres is markedly higher in germ-free than in SPF mice, and winner B cells in germ-free germinal centres are enriched in 'public' clonotypes found in multiple individuals, indicating strong selection of B cell antigen receptors even in the absence of microbiota. Colonization of germ-free mice with a defined microbial consortium (Oligo-MM12) does not eliminate germ-free-associated clonotypes, yet does induce a concomitant commensal-specific B cell response with the hallmarks of antigen-driven selection. Thus, positive selection of B cells can take place in steady-state gut-associated germinal centres, at a rate that is tunable over a wide range by the presence and composition of the microbiota.

Author Correction: Microbiota modulate sympathetic neurons via a gut-brain circuit.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Microbiota modulate sympathetic neurons via a gut-brain circuit.

Connections between the gut and brain monitor the intestinal tissue and its microbial and dietary content1, regulating both physiological intestinal functions such as nutrient absorption and motility2,3, and brain-wired feeding behaviour2. It is therefore plausible that circuits exist to detect gut microorganisms and relay this information to areas of the central nervous system that, in turn, regulate gut physiology4. Here we characterize the influence of the microbiota on enteric-associated neurons by combining gnotobiotic mouse models with transcriptomics, circuit-tracing methods and functional manipulations. We find that the gut microbiome modulates gut-extrinsic sympathetic neurons: microbiota depletion leads to increased expression of the neuronal transcription factor cFos, and colonization of germ-free mice with bacteria that produce short-chain fatty acids suppresses cFos expression in the gut sympathetic ganglia. Chemogenetic manipulations, translational profiling and anterograde tracing identify a subset of distal intestine-projecting vagal neurons that are positioned to have an afferent role in microbiota-mediated modulation of gut sympathetic neurons. Retrograde polysynaptic neuronal tracing from the intestinal wall identifies brainstem sensory nuclei that are activated during microbial depletion, as well as efferent sympathetic premotor glutamatergic neurons that regulate gastrointestinal transit. These results reveal microbiota-dependent control of gut-extrinsic sympathetic activation through a gut-brain circuit.

Longitudinal analyses reveal immunological misfiring in severe COVID-19.

Recent studies have provided insights into the pathogenesis of coronavirus disease 2019 (COVID-19)1-4. However, the longitudinal immunological correlates of disease outcome remain unclear. Here we serially analysed immune responses in 113 patients with moderate or severe COVID-19. Immune profiling revealed an overall increase in innate cell lineages, with a concomitant reduction in T cell number. An early elevation in cytokine levels was associated with worse disease outcomes. Following an early increase in cytokines, patients with moderate COVID-19 displayed a progressive reduction in type 1 (antiviral) and type 3 (antifungal) responses. By contrast, patients with severe COVID-19 maintained these elevated responses throughout the course of the disease. Moreover, severe COVID-19 was accompanied by an increase in multiple type 2 (anti-helminths) effectors, including interleukin-5 (IL-5), IL-13, immunoglobulin E and eosinophils. Unsupervised clustering analysis identified four immune signatures, representing growth factors (A), type-2/3 cytokines (B), mixed type-1/2/3 cytokines (C), and chemokines (D) that correlated with three distinct disease trajectories. The immune profiles of patients who recovered from moderate COVID-19 were enriched in tissue reparative growth factor signature A, whereas the profiles of those with who developed severe disease had elevated levels of all four signatures. Thus, we have identified a maladapted immune response profile associated with severe COVID-19 and poor clinical outcome, as well as early immune signatures that correlate with divergent disease trajectories.

Compartmentalized gut lymph node drainage dictates adaptive immune responses.

The intestinal immune system has the challenging task of tolerating foreign nutrients and the commensal microbiome, while excluding or eliminating ingested pathogens. Failure of this balance leads to conditions such as inflammatory bowel diseases, food allergies and invasive gastrointestinal infections1. Multiple immune mechanisms are therefore in place to maintain tissue integrity, including balanced generation of effector T (TH) cells and FOXP3+ regulatory T (pTreg) cells, which mediate resistance to pathogens and regulate excessive immune activation, respectively1-4. The gut-draining lymph nodes (gLNs) are key sites for orchestrating adaptive immunity to luminal perturbations5-7. However, it is unclear how they simultaneously support tolerogenic and inflammatory reactions. Here we show that gLNs are immunologically specific to the functional gut segment that they drain. Stromal and dendritic cell gene signatures and polarization of T cells against the same luminal antigen differ between gLNs, with the proximal small intestine-draining gLNs preferentially giving rise to tolerogenic responses and the distal gLNs to pro-inflammatory T cell responses. This segregation permitted the targeting of distal gLNs for vaccination and the maintenance of duodenal pTreg cell induction during colonic infection. Conversely, the compartmentalized dichotomy was perturbed by surgical removal of select distal gLNs and duodenal infection, with effects on both lymphoid organ and tissue immune responses. Our findings reveal that the conflict between tolerogenic and inflammatory intestinal responses is in part resolved by discrete gLN drainage, and encourage antigen targeting to specific gut segments for therapeutic immune modulation.

The effect of parenting behaviours on adolescents' rumination: a systematic review of longitudinal studies.

Rumination is an emotional regulation mechanism strongly associated with the development and maintenance of internalising psychopathology in adolescence and adulthood. Parenting behaviours (PBs) play a pivotal role in the development of rumination in children and adolescents. Nonetheless, the specific PBs that can either protect against or increase the risk of rumination development remain poorly understood. This systematic review aimed to explore the (1) temporal associations between PBs and adolescents' rumination and (2) potential moderators influencing these associations. We conducted a comprehensive search across Web of Science, Scopus, PubMed, Academic Search Complete and Eric databases, adhering to PRISMA reporting guidelines. Out of 1,868 abstracts screened, 182 articles underwent full-text examination, with nine meeting the inclusion criteria for the systematic review. Overall, the studies indicated that PBs characterised by criticism, rejection and control were positively associated with the development of rumination in adolescents, whilst PBs marked by authoritative practises exhibited a negative association with rumination. Gender, temperament, environmental sensitivity and pubertal timing emerged as significant moderators in the effects of PBs on rumination. However, conclusions were limited due to the studies' methodological heterogeneity. Future studies on PBs and rumination should address various dimensions of PBs and different moderators to identify factors that can modify the development of rumination across adolescence. Findings may inform family-based prevention programmes to promote emotion regulation in adolescents as a protective factor against internalising psychopathology across adulthood.

[Insulin autoimmune syndrome : A rare, but important differential diagnosis of hypoglycemia]. / Insulinautoimmunsyndrom : Eine seltene, aber wichtige Differentialdiagnose der Hypoglykämie.

A 69-year-old female patient was referred to the Medical University of Hanover for further diagnostic evaluation of recurrent severe hypoglycemia. The patient had previously been started on clopidogrel after arterial stenting for peripheral arterial obstructive disease (PAOD). The presence of an insulinoma and paraneoplastic syndrome was excluded. Increased serum insulin and insulin autoantibodies levels were confirmed, despite normal to low blood sugar levels. An insulin autoimmune syndrome was diagnosed, most likely induced by the prior intake of clopidogrel. Treatment with immunoadsorption was initiated, achieving a significant reduction in hypoglycemic events and a lasting response to treatment over 3 months.

Red Tomato Products as an Alternative to Reduce Synthetic Dyes in the Food Industry: A Review.

Most dyes used in the food industry are synthetic and can be a health hazard. Red tomato may serve as a natural alternative dye to replace synthetic colorants. This study aimed to review the literature on the addition of red tomato products (powder tomato, paste, freeze-dried, tomato peel powder, tomato pomace) to reduce the usage of synthetic dyes in the food industry. Red tomato products have been used as coloring in pasta, bologna, sausages, cookies, crackers, macaroons, hamburgers, breads, muffins, cheeses, and nuggets. The trans-cis isomerization of lycopene by oxidative processes directly affects the color of the pigment. The lycopene contained in tomato has antioxidant activity and could reduce or eliminate other oxidants and/or synthetic preservatives in food. Moreover, tomatoes in foods have high sensory scores, nutritional appeal, and marketing potential. However, its use as a food colorant has been not extensively explored. Therefore, further studies are still required, especially on the stability of carotenoids in tomatoes used in processed foods.

[Best supportive care in a young patient with locally advanced MSI-high colon cancer?] / Best supportive care bei einer jungen Patientin mit lokal fortgeschrittenem MSI-high-Kolonkarzinom?

Molecular diagnostics are increasingly important to guide treatment decisions in oncologic patients. For instance, the presence of high-grade microsatellite-instability (MSI-high) is considered to be one of the major positive predictors of therapy response to immune-checkpoint inhibitors in patients with solid tumors. Based on impressive results from several immune-oncology trials, the American Food and Drug Administration (FDA) granted approval to immunotherapy in any previously treated, MSI-high solid cancer in 2017. Here, we report the clinical case of a young patient with MSI-high colorectal cancer. The case illustrates, that insurance companies in Germany are still reluctant to cover the cost of immunotherapy in this specific patient subgroup, which, in our opinion, results in an ethically problematic therapeutic dilemma.

Skin wound healing is accelerated and scarless in the absence of commensal microbiota.

The commensal microbiota has a high impact on health and disease by modulating the development and homeostasis of host immune system. Immune cells are involved in virtually every aspect of the wound repair process; however, the impact of commensal microbiota on skin wound healing is largely unknown. In this study, we evaluated the influence of commensal microbiota on tissue repair of excisional skin wounds by using germ-free (GF) Swiss mice. We observed that macroscopic wound closure rate is accelerated in the absence of commensal microbiota. Accordantly, histologically assessed wound epithelization was accelerated in GF in comparison with conventional (CV) Swiss mice. The wounds of GF mice presented a significant decrease in neutrophil accumulation and an increase in mast cell and macrophage infiltration into wounds. Interestingly, alternatively activated healing macrophage-related genes were highly expressed in the wound tissue of GF mice. Moreover, levels of the anti-inflammatory cytokine IL-10, the angiogenic growth factor VEGF and angiogenesis were higher in the wound tissue of those mice. Conversely, scarring and levels of the profibrogenic factor TGF-ß1 were greatly reduced in GF mice wounded skin when compared with CV mice. Of note, conventionalization of GF mice with CV microbiota restored wound closure rate, neutrophil and macrophage accumulation, cytokine production, and scarring to the same extent as CV mice. Overall, our findings suggest that, in the absence of any contact with microbiota, skin wound healing is accelerated and scarless, partially because of reduced accumulation of neutrophils, increased accumulation of alternatively activated healing macrophages, and better angiogenesis at wound sites.

Dietary protein shapes the profile and repertoire of intestinal CD4 + T cells.

The intestinal immune system must tolerate food antigens to avoid allergy, a process requiring CD4 + T cells. Combining antigenically defined diets with gnotobiotic models, we show that food and microbiota distinctly influence the profile and T cell receptor repertoire of intestinal CD4 + T cells. Independent of the microbiota, dietary proteins contributed to accumulation and clonal selection of antigen-experienced CD4 + T cells at the intestinal epithelium, imprinting a tissue specialized transcriptional program including cytotoxic genes on both conventional and regulatory CD4 + T cells (Tregs). This steady state CD4 + T cell response to food was disrupted by inflammatory challenge, and protection against food allergy in this context was associated with Treg clonal expansion and decreased pro-inflammatory gene expression. Finally, we identified both steady state epithelium-adapted CD4 + T cells and tolerance-induced Tregs that recognize dietary antigens, suggesting that both cell types may be critical for preventing inappropriate immune responses to food.

Dietary protein shapes the profile and repertoire of intestinal CD4+ T cells.

The intestinal immune system must tolerate food antigens to avoid allergy, a process requiring CD4+ T cells. Combining antigenically defined diets with gnotobiotic models, we show that food and microbiota distinctly influence the profile and T cell receptor repertoire of intestinal CD4+ T cells. Independent of the microbiota, dietary proteins contributed to accumulation and clonal selection of antigen-experienced CD4+ T cells at the intestinal epithelium, imprinting a tissue-specialized transcriptional program including cytotoxic genes on both conventional and regulatory CD4+ T cells (Tregs). This steady state CD4+ T cell response to food was disrupted by inflammatory challenge, and protection against food allergy in this context was associated with Treg clonal expansion and decreased proinflammatory gene expression. Finally, we identified both steady-state epithelium-adapted CD4+ T cells and tolerance-induced Tregs that recognize dietary antigens, suggesting that both cell types may be critical for preventing inappropriate immune responses to food.

Progression of a Rare Disease, Takayasu Arteritis, With Hematologic and Gastrointestinal Manifestations: A Four-Year Follow-Up Study.

Takayasu arteritis (TA) is a heterogeneous disease whose presentation and progression have not yet been well described. An elderly female was diagnosed with TA after presenting with bilateral arm claudication, elevated ESR, and bilateral subclavian arterial stenosis. In the first two years after diagnosis, she was diagnosed with monoclonal gammopathy of undetermined significance and alpha thalassemia minor. For the next two years, she presented with a non-ST elevation myocardial infarction, three oozing Dieulafoy lesions, and eosinophilic esophagitis. As we observed, TA can have an unusual and unpredictable progression. Therefore, a multidisciplinary approach and clinical surveillance are paramount.

Suppression of epithelial proliferation and tumorigenesis by immunoglobulin A.

Immunoglobulin A (IgA) is the most abundant antibody isotype produced across mammals and plays a specialized role in mucosal homeostasis 1 . Constantly secreted into the lumen of the intestine, IgA binds commensal microbiota to regulate their colonization and function 2,3 , with unclear implications for health. IgA deficiency is common in humans but is difficult to study due to its complex etiology and comorbidities 4-8 . Using genetically and environmentally controlled mice, here we show that IgA-deficient animals have a baseline alteration in the colon epithelium that increases susceptibility to multiple models of colorectal cancer. Transcriptome, imaging, and flow cytometry-based analyses revealed that, in the absence of IgA, colonic epithelial cells induce antibacterial factors and accelerate cell cycling in response to the microbiota. Oral treatment with IgA was sufficient to suppress aberrant epithelial proliferation independently of bacterial binding, suggesting that IgA provides a feedback signal to epithelial cells in parallel with its known roles in microbiome shaping. In a primary colonic organoid culture system, IgA directly suppresses epithelial growth. Conversely, the susceptibility of IgA-deficient mice to colorectal cancer was reversed by Notch inhibition to suppress the absorptive colonocyte developmental program, or by inhibition of the cytokine MIF, the receptor for which was upregulated in stem cells of IgA-deficient animals. These studies demonstrate a homeostatic function for IgA in tempering physiological epithelial responses to microbiota to maintain mucosal health.

Outcomes With Peripheral Venoarterial Extracorporeal Membrane Oxygenation for Suspected Acute Myocarditis: 10-Year Experience From the Extracorporeal Life Support Organization Registry.

BACKGROUND: Acute myocarditis can result in severe hemodynamic compromise requiring venoarterial extracorporeal membrane oxygenation (VA-ECMO). Outcomes and factors associated with mortality among myocarditis patients are not well described in the modern ECMO era. METHODS: We queried the Extracorporeal Life Support Organization registry from 2011 to 2020 for adults with suspected acute myocarditis undergoing peripheral VA-ECMO support. The primary outcome was in-hospital mortality and was compared to all-comers receiving VA-ECMO in the registry over the same period. Secondary outcomes were rates of bridging to advanced therapies and ECMO complications. We used multivariable logistic regression to examine factors associated with in-hospital mortality. RESULTS: Among 850 patients with suspected acute myocarditis receiving peripheral VA-ECMO, the mean age was 41 years, 52% were men, 39% Asian race, and 14.8% underwent extracorporeal cardiopulmonary resuscitation. During the study period, in-hospital mortality steadily declined and was 58.3% for all all-comers receiving VA-ECMO compared with 34.9% for patients with myocarditis (P<0.001). After multivariable modeling, risk factors for mortality were earlier year of support, older age, higher weight, Asian race, need for extracorporeal cardiopulmonary resuscitation, sepsis, and lower mean arterial pressure and pH prior to ECMO initiation. ECMO complications including bleeding, limb ischemia, infections and ischemic stroke were more common among nonsurvivors and significantly declined during the study period. CONCLUSIONS: Compared with all-comers supported with VA-ECMO, in-hospital mortality for patients with acute myocarditis is significantly lower, with nearly two-thirds of patients surviving to discharge. Major modifiable risk factors for mortality were ongoing cardiopulmonary resuscitation requiring ECMO and markers of illness severity prior to ECMO.

Immune Checkpoint Inhibitors for Child-Pugh Class B Advanced Hepatocellular Carcinoma: A Systematic Review and Meta-Analysis.

Importance: Immune checkpoint inhibitors (ICIs) are increasingly used in patients with advanced hepatocellular carcinoma (HCC). However, data on ICI therapy in patients with advanced HCC and impaired liver function are scarce. Objective: To conduct a systematic review and meta-analysis to determine the efficacy and safety of ICI treatment for advanced HCC with Child-Pugh B liver function. Data Sources: PubMed, Embase, Web of Science, and Cochrane Library were searched for relevant studies from inception through June 15, 2022. Study Selection: Randomized clinical trials, cohort studies, or single-group studies that investigated the efficacy or safety of ICI therapy for Child-Pugh B advanced HCC were included. Data Extraction and Synthesis: The Preferred Reporting Items for Systematic Reviews and Meta-Analysis guideline was followed to extract data. A random-effects model was adopted if the heterogeneity was significant (I2 > 50%); otherwise, a fixed-effect model was used. Main Outcomes and Measures: The objective response rate (ORR) and overall survival (OS) were considered to be the primary efficacy outcomes of ICI treatment for Child-Pugh B advanced HCC, and the incidence of treatment-related adverse events (trAEs) was set as the primary measure for the safety outcome. Results: A total of 22 studies including 699 patients with Child-Pugh B and 2114 with Child-Pugh A advanced HCC comprised the analytic sample (median age range, 53-73 years). Upon pooled analysis, patients treated with ICIs in the Child-Pugh B group had an ORR of 14% (95% CI, 11%-17%) and disease control rate (DCR) of 46% (95% CI, 36%-56%), with a median OS of 5.49 (95% CI, 3.57-7.42) months and median progression-free survival of 2.68 (95% CI, 1.85-3.52) months. The rate of any grade trAEs in the Child-Pugh B group was 40% (95% CI, 34%-47%) and of grade 3 or higher trAEs was 12% (95% CI, 6%-23%). Compared with the Child-Pugh A group, the ORR (odds ratio, 0.59; 95% CI, 0.43-0.81; P < .001) and DCR (odds ratio, 0.64; 95% CI, 0.50-0.81; P < .001) were lower in the Child-Pugh B group. Child-Pugh B was independently associated with worse OS in patients with advanced HCC treated with ICIs (hazard ratio, 2.72 [95% CI, 2.34-3.16]; adjusted hazard ratio, 2.33 [95% CI, 1.81-2.99]). However, ICIs were not associated with increased trAEs in the Child-Pugh B group. Conclusions and Relevance: The findings of this systematic review and meta-analysis suggest that although the safety of ICI treatment was comparable between patients with HCC with vs without advanced liver disease and the treatment resulted in a significant number of radiologic responses, survival outcomes are still inferior in patients with worse liver function. More study is needed to determine the effectiveness of ICI treatment in this population.