Epithelial colonization by gut dendritic cells promotes their functional diversification.

Dendritic cells (DCs) patrol tissues and transport antigens to lymph nodes to initiate adaptive immune responses. Within tissues, DCs constitute a complex cell population composed of distinct subsets that can exhibit different activation states and functions. How tissue-specific cues orchestrate DC diversification remains elusive. Here, we show that the small intestine included two pools of cDC2s originating from common pre-DC precursors: (1) lamina propria (LP) CD103+CD11b+ cDC2s that were mature-like proinflammatory cells and (2) intraepithelial cDC2s that exhibited an immature-like phenotype as well as tolerogenic properties. These phenotypes resulted from the action of food-derived retinoic acid (ATRA), which enhanced actomyosin contractility and promoted LP cDC2 transmigration into the epithelium. There, cDC2s were imprinted by environmental cues, including ATRA itself and the mucus component Muc2. Hence, by reaching distinct subtissular niches, DCs can exist as immature and mature cells within the same tissue, revealing an additional mechanism of DC functional diversification.

Oxysterol Sensing through the Receptor GPR183 Promotes the Lymphoid-Tissue-Inducing Function of Innate Lymphoid Cells and Colonic Inflammation.

Group 3 innate lymphoid cells (ILC3s) sense environmental signals and are critical for tissue integrity in the intestine. Yet, which signals are sensed and what receptors control ILC3 function remain poorly understood. Here, we show that ILC3s with a lymphoid-tissue-inducer (LTi) phenotype expressed G-protein-coupled receptor 183 (GPR183) and migrated to its oxysterol ligand 7α,25-hydroxycholesterol (7α,25-OHC). In mice lacking Gpr183 or 7α,25-OHC, ILC3s failed to localize to cryptopatches (CPs) and isolated lymphoid follicles (ILFs). Gpr183 deficiency in ILC3s caused a defect in CP and ILF formation in the colon, but not in the small intestine. Localized oxysterol production by fibroblastic stromal cells provided an essential signal for colonic lymphoid tissue development, and inflammation-induced increased oxysterol production caused colitis through GPR183-mediated cell recruitment. Our findings show that GPR183 promotes lymphoid organ development and indicate that oxysterol-GPR183-dependent positioning within tissues controls ILC3 activity and intestinal homeostasis.

Impact that the COVID-19 pandemic on routine childhood vaccinations and challenges ahead: A narrative review.

AIM: To document the decline in vaccination coverage in the first months of 2020 as an indirect effect of the COVID-19 pandemic. METHODS: We performed a literature review in medical databases. Overall, 143 articles were initially retrieved, out of which 48 were selected and included in the review. RESULTS: Our review retrieved similar data in many countries worldwide, and, globally, preliminary data from the first 4 months of 2020 indicate a decline in diphtheria-tetanus-pertussis coverage, generally considered the marker of vaccination coverage across countries. World Health Organization recommends maintaining vaccination services, prioritising primary series vaccinations especially for measles-rubella or poliomyelitis, but it also lets each country decide whether to maintain the immunisation services evaluating the current epidemiology of vaccine-preventable diseases and the COVID-19 local transmission scenario. Successively, recovering of vaccinations should be planned. Moreover, during the pandemic, influenza vaccination should be promoted as a central public health measure. CONCLUSION: Future challenges will be to maintain the vaccination programmes, especially in children younger than 2 years old and adolescents, to plan the recovery of vaccinations for subjects who postponed them during the lockdown, and to early identify any vaccine-preventable disease outbreak.

What the paediatrician needs to know about HIV-1 infection.

Nowadays, it is spreading the false perception that pediatric HIV infection has been almost completely disappeared in Italy, as well as in other Western countries, and it does not deserve the attention of the primary care pediatrician anymore. Hereby, we report the important role still played by the primary care pediatrician in management and prevention of pediatric HIV infection in Western countries.

Multi-faceted inhibition of dendritic cell function by CD4+Foxp3+ regulatory T cells.

CTLA-4 is required for CD4+Foxp3+ regulatory T (Treg) cell function, but its mode of action remains incompletely defined. Herein we generated Ctla-4ex2fl/flFoxp3-Cre mice with Treg cells exclusively expressing a naturally occurring, ligand-independent isoform of CTLA-4 (liCTLA-4) that cannot interact with the costimulatory molecules CD80 and CD86. The mice did not exhibit any signs of effector T cell activation early in life, however, at 6 months of age they exhibited excessive T cell activation and inflammation in lungs. In contrast, mice with Treg cells completely lacking CTLA-4 developed lymphoproliferative disease characterized by multi-organ inflammation early in life. In vitro, Treg cells exclusively expressing liCTLA-4 inhibited CD80 and CD86 expression on dendritic cells (DC). Conversely, Treg cells required the extra-cellular part of CTLA-4 to up-regulate expression of the co-inhibitory molecule PD-L2 on DCs. Transcriptomic analysis of suppressed DCs revealed that Treg cells induced a specific immunosuppressive program in DCs.

Giant palatal schwannoma.

Schwannoma is a benign tumor that arises from nerves that contain Schwann cells. We report a case of giant schwannoma of the hard palate, which originated from the greater palatine nerve and is interesting for its large dimensions.

Diaphragmatic hernia in a term newborn with congenital myotonic dystrophy: case report.

Background and aim Myotonic dystrophy (DM) is a genetic disorder determined by an amplified trinucleotide CTG repeat in the untranslated region of the DMPK gene on chromosome 19q13.3. The incidence of the congenital form is 1 in 47619 live births and the mortality in the neonatal period is up to 40%. Methods: We report a case of congenital DM (CDM, also designated Myotonic Dystrophy Type 1), presented with congenital right diaphragmatic hernia and cerebral bilateral ventricular dilatation, genetically diagnosed. Conclusions: Since no case of congenital diaphragmatic hernia associated with CDM is reported, the present case report could be considered of particular interest.

The use of antiviral drugs in children.

Viral infections are particularly common among children. They often have a mild course, are self-limiting and do not need any specific treatment. However, in some cases, the disease can be severe and lead to permanent disabilities. A variety of antiviral drugs are available for the treatments of certain infectious agents: for instance, acyclovir is used to treat herpes simplex virus encephalitis. Recommendations for flu treatment may change according to the current epidemiological surveillance data, on the basis of which antiviral sensibility can be forecast: recommended drugs for the 2020-21 flu season are oseltamivir, zanamivir, peramivir and baloxavir. Some drugs are used to treat congenital infections, such as valganciclovir and ganciclovir in congenital cytomegalovirus infection. Antiretroviral prophylaxis in newborns from HIV-1 infected mothers must be initiated as soon as possible, with one or more drugs according to therapeutic regimens based on the baby's risk category. According to the most recent guidelines, antiretroviral therapy must be started at diagnosis. Several antiretroviral drugs are available today and approved for use in children, so several combinations can be made. However, out of the 29 antiretroviral drugs approved for adults, only 38% (11/29) are approved for children under the age of two and about 60% (18/29) for children under the age of twelve. Treatment with direct antiviral agents against hepatitis C virus is approved for children over the age of three; it consists in different therapeutic regimens chosen on the basis of the viral genotype (ledipasvir/sofosbuvir for genotypes 1, 4, 5 and 6, sofosbuvir/ribavirin for genotypes 2 and 3, sofosbuvir/velpatasvir and glecaprevir/pibrentasvir for all genotypes) and it has dramatically changed the course of the illness. Many molecules have been studied in order to treat SARS-CoV-2 infection, but only remdesivir seems to play a role in shortening recovery time, although inclusion criteria are very specific and data on the use in children is limited.

Interleukin-10 regulates goblet cell numbers through Notch signaling in the developing zebrafish intestine.

Cytokines are immunomodulatory proteins that orchestrate cellular networks in health and disease. Among these, interleukin (IL)-10 is critical for the establishment of intestinal homeostasis, as mutations in components of the IL-10 signaling pathway result in spontaneous colitis. Whether IL-10 plays other than immunomodulatory roles in the intestines is poorly understood. Here, we report that il10, il10ra, and il10rb are expressed in the zebrafish developing intestine as early as 3 days post fertilization. CRISPR/Cas9-generated il10-deficient zebrafish larvae showed an increased expression of pro-inflammatory genes and an increased number of intestinal goblet cells compared to WT larvae. Mechanistically, Il10 promotes Notch signaling in zebrafish intestinal epithelial cells, which in turn restricts goblet cell expansion. Using murine organoids, we showed that IL-10 modulates goblet cell frequencies in mammals, suggesting conservation across species. This study demonstrates a previously unappreciated IL-10-Notch axis regulating goblet cell homeostasis in the developing zebrafish intestine and may help explain the disease severity of IL-10 deficiency in the intestines of mammals.

The spatial transcriptomic landscape of the healing mouse intestine following damage.

The intestinal barrier is composed of a complex cell network defining highly compartmentalized and specialized structures. Here, we use spatial transcriptomics to define how the transcriptomic landscape is spatially organized in the steady state and healing murine colon. At steady state conditions, we demonstrate a previously unappreciated molecular regionalization of the colon, which dramatically changes during mucosal healing. Here, we identified spatially-organized transcriptional programs defining compartmentalized mucosal healing, and regions with dominant wired pathways. Furthermore, we showed that decreased p53 activation defined areas with increased presence of proliferating epithelial stem cells. Finally, we mapped transcriptomics modules associated with human diseases demonstrating the translational potential of our dataset. Overall, we provide a publicly available resource defining principles of transcriptomic regionalization of the colon during mucosal healing and a framework to develop and progress further hypotheses.

Epidemiology and Management of Acute Hematogenous Osteomyelitis, Neonatal Osteomyelitis and Spondylodiscitis in a Third Level Paediatric Center.

Acute hematogenous osteomyelitis (AHOM) is a rare pathology in pediatric population. The aim of this study is to analyse the epidemiological data and the management, compared to European Society for Paediatric Infectious Disease (ESPID, European Society for Pediatric Infectious Diseases) guidelines 2017 of 216 children with AHOM, divided in three cohorts (neonatal-onset osteomyelitis, those with vertebral involvement and other types of osteomyelitis). We conducted a retrospective single center study, evaluating data from all the children (aged 0-18 years) consecutively admitted to the Meyer Children's Hospital, during a period of ten years (1 January 2010-31 December 2019). Isolation of pathogen was possible in 65 patients and S. aureus was the most frequently involved (43/65 children). Magnetic Resonance Imaging (MRI, magnetic resonance imaging) was performed in 201/216 cases and was compatible with osteomyelitis in 185/201 of these children (92.03%). In the neonatal-onset osteomyelitis group the percentage of diagnostic ultrasound for osteomyelitis was 36.36% significantly higher than the other groups. The median duration of total antibiotic therapy was 37.5 days. In total, 186/199 children recovered without complications. The present study delineates three heterogeneous cohorts of patients. S. aureus is confirmed as the first pathogen for isolation in all three groups analysed. MRI represent a gold standard for diagnosis. Longer duration of antibiotics treatment was performed in neonatal and spondylodiscitis group, compared to the other types of osteomyelitis.

Liver X receptor regulates Th17 and RORγt+ Treg cells by distinct mechanisms.

The gastrointestinal microenvironment, dominated by dietary compounds and the commensal bacteria, is a major driver of intestinal CD4+ T helper (Th) cell differentiation. Dietary compounds can be sensed by nuclear receptors (NRs) that consequently exert pleiotropic effects including immune modulation. Here, we found that under homeostatic conditions the NR Liver X receptor (LXR), a sensor of cholesterol metabolites, regulates RORγt+ CD4 T cells in the intestine draining mesenteric lymph node (MLN). While LXR activation led to a decrease, LXR-deficiency resulted in an increase in MLN Th17 and RORγt+ Tregs. Mechanistically, LXR signaling in CD11c+ myeloid cells was required to control RORγt+ Treg. By contrast, modulation of MLN Th17 was independent of LXR signaling in either immune or epithelial cells. Of note, horizontal transfer of microbiota between LXRα-/- and WT mice was sufficient to only partially increase MLN Th17 in WT mice. Despite LXRα deficiency resulted in an increased abundance of Ruminococcaceae and Lachnospiraceae bacterial families compared to littermate controls, microbiota ablation (including SFB) was not sufficient to dampen LXRα-mediated expansion of MLN Th17. Altogether, our results suggest that LXR modulates RORγt+ Treg and Th17 cells in the MLN through distinct mechanisms.

Tuberculosis and TNF-α inhibitors in children: how to manage a fine balance.

Since the introduction of biologic response modifiers (BRMs) in the management of children affected by the immune-mediated inflammatory disease, these patients substantially improved their quality of life. BRMs are generally well tolerated and effective in most children and adolescents refractory to conventional immunosuppressive therapy. On the other hand, patients receiving BRMs, especially TNF-α inhibitors, display an increased risk of primary infections or reactivations, i.e. due to Mycobacterium tuberculosis. M. tuberculosis can cause severe disease with consequent short- and long-term morbidity in children on anti-TNF-α treatment. The present paper analyses the increased risk of reactivation of latent tuberculosis infection (LTBI) or de novo TB infection in children treated with TNF-α inhibitors, with the purpose to provide recommendations for screening strategies and safety monitoring of paediatric patients. Special attention is also given to the currently available TB screening tools (IGRAs and TST) and their utility in the diagnosis of LTBI before starting the biologic therapy and during the treatment. Finally, the paper analyses the suggested TB-preventing therapies to adopt in these children and the correct timing to overlap anti-TB and anti-TNF-a treatment.

Conserved transcriptomic profile between mouse and human colitis allows unsupervised patient stratification.

Clinical manifestations and response to therapies in ulcerative colitis (UC) are heterogeneous, yet patient classification criteria for tailored therapies are currently lacking. Here, we present an unsupervised molecular classification of UC patients, concordant with response to therapy in independent retrospective cohorts. We show that classical clustering of UC patient tissue transcriptomic data sets does not identify clinically relevant profiles, likely due to associated covariates. To overcome this, we compare cross-sectional human data sets with a newly generated longitudinal transcriptome profile of murine DSS-induced colitis. We show that the majority of colitis risk-associated gene expression peaks during the inflammatory rather than the recovery phase. Moreover, we achieve UC patient clustering into two distinct transcriptomic profiles, differing in neutrophil-related gene activation. Notably, 87% of patients in UC1 cluster are unresponsive to two most widely used biological therapies. These results demonstrate that cross-species comparison enables stratification of patients undistinguishable by other molecular approaches.

Flt3 ligand expands bona fide innate lymphoid cell precursors in vivo.

A common helper-like innate lymphoid precursor (CHILP) restricted to the innate lymphoid cells (ILC) lineage has been recently characterized. While specific requirements of transcription factors for CHILPs development has been partially described, their ability to sense cytokines and react to peripheral inflammation remains unaddressed. Here, we found that systemic increase in Flt3L levels correlated with the expansion of Lineage (Lin)negα4ß7+ precursors in the adult murine bone marrow. Expanded Linnegα4ß7+ precursors were bona fide CHILPs as seen by their ability to differentiate into all helper ILCs subsets but cNK in vivo. Interestingly, Flt3L-expanded CHILPs transferred into lymphopenic mice preferentially reconstituted the small intestine. While we did not observe changes in serum Flt3L during DSS-induced colitis in mice or plasma from inflammatory bowel disease (IBD) patients, elevated Flt3L levels were detected in acute malaria patients. Interestingly, while CHILP numbers were stable during the course of DSS-induced colitis, they expanded following increased serum Flt3L levels in malaria-infected mice, hence suggesting a role of the Flt3L-ILC axis in malaria. Collectively, our results indicate that Flt3L expands CHILPs in the bone marrow, which might be associated with specific inflammatory conditions.

Molecular and functional heterogeneity of IL-10-producing CD4+ T cells.

IL-10 is a prototypical anti-inflammatory cytokine, which is fundamental to the maintenance of immune homeostasis, especially in the intestine. There is an assumption that cells producing IL-10 have an immunoregulatory function. However, here we report that IL-10-producing CD4+ T cells are phenotypically and functionally heterogeneous. By combining single cell transcriptome and functional analyses, we identified a subpopulation of IL-10-producing Foxp3neg CD4+ T cells that displays regulatory activity unlike other IL-10-producing CD4+ T cells, which are unexpectedly pro-inflammatory. The combinatorial expression of co-inhibitory receptors is sufficient to discriminate IL-10-producing CD4+ T cells with regulatory function from others and to identify them across different tissues and disease models in mice and humans. These regulatory IL-10-producing Foxp3neg CD4+ T cells have a unique transcriptional program, which goes beyond the regulation of IL-10 expression. Finally, we found that patients with Inflammatory Bowel Disease demonstrate a deficiency in this specific regulatory T-cell subpopulation.

Retinoic Acid and Its Role in Modulating Intestinal Innate Immunity.

Vitamin A (VA) is amongst the most well characterized food-derived nutrients with diverse immune modulatory roles. Deficiency in dietary VA has not only been associated with immune dysfunctions in the gut, but also with several systemic immune disorders. In particular, VA metabolite all-trans retinoic acid (atRA) has been shown to be crucial in inducing gut tropism in lymphocytes and modulating T helper differentiation. In addition to the widely recognized role in adaptive immunity, increasing evidence identifies atRA as an important modulator of innate immune cells, such as tolerogenic dendritic cells (DCs) and innate lymphoid cells (ILCs). Here, we focus on the role of retinoic acid in differentiation, trafficking and the functions of innate immune cells in health and inflammation associated disorders. Lastly, we discuss the potential involvement of atRA during the plausible crosstalk between DCs and ILCs.

Breast Milk and Solid Food Shaping Intestinal Immunity.

After birth, the intestinal immune system enters a critical developmental stage, in which tolerogenic and pro-inflammatory cells emerge to contribute to the overall health of the host. The neonatal health is continuously challenged by microbial colonization and food intake, first in the form of breast milk or formula and later in the form of solid food. The microbiota and dietary compounds shape the newborn immune system, which acquires the ability to induce tolerance against innocuous antigens or induce pro-inflammatory immune responses against pathogens. Disruption of these homeostatic mechanisms might lead to undesired immune reactions, such as food allergies and inflammatory bowel disease. Hence, a proper education and maturation of the intestinal immune system is likely important to maintain life-long intestinal homeostasis. In this review, the most recent literature regarding the effects of dietary compounds in the development of the intestinal immune system are discussed.

Tenascin-C Protects Cancer Stem-like Cells from Immune Surveillance by Arresting T-cell Activation.

Precociously disseminated cancer cells may seed quiescent sites of future metastasis if they can protect themselves from immune surveillance. However, there is little knowledge about how such sites might be achieved. Here, we present evidence that prostate cancer stem-like cells (CSC) can be found in histopathologically negative prostate draining lymph nodes (PDLN) in mice harboring oncogene-driven prostate intraepithelial neoplasia (mPIN). PDLN-derived CSCs were phenotypically and functionally identical to CSC obtained from mPIN lesions, but distinct from CSCs obtained from frank prostate tumors. CSC derived from either PDLN or mPIN used the extracellular matrix protein Tenascin-C (TNC) to inhibit T-cell receptor-dependent T-cell activation, proliferation, and cytokine production. Mechanistically, TNC interacted with α5ß1 integrin on the cell surface of T cells, inhibiting reorganization of the actin-based cytoskeleton therein required for proper T-cell activation. CSC from both PDLN and mPIN lesions also expressed CXCR4 and migrated in response to its ligand CXCL12, which was overexpressed in PDLN upon mPIN development. CXCR4 was critical for the development of PDLN-derived CSC, as in vivo administration of CXCR4 inhibitors prevented establishment in PDLN of an immunosuppressive microenvironment. Taken together, our work establishes a pivotal role for TNC in tuning the local immune response to establish equilibrium between disseminated nodal CSC and the immune system.