A real-life pediatric experience of Crohn's disease exclusion diet at disease onset and in refractory patients.

OBJECTIVES: We aimed to appraise the real-life efficacy of Crohn's disease exclusion diet (CDED) coupled with partial enteral nutrition (PEN) in inducing clinical and biochemical remission at disease onset and in patients with loss of response to biologics and immunomodulators. METHODS: We retrospectively gathered data of patients aged less than 18 years of age with a diagnosis of Crohn's disease (CD), who received CDED coupled with PEN at a tertiary level pediatric inflammatory bowel disease center. RESULTS: Sixty-six patients were identified. Forty (60.6%) started CDED plus PEN at disease onset and 26 (39.4%) received CDED with PEN as add-on therapy. Forty-six (69.7%) patients achieved clinical remission (weighted Pediatric Crohn's Disease Activity Index < 12.5) at the end of phase 1, 44 (66.7%) normalized c-reactive protein levels (<0.5 mg/dL) and 18 (27.2%) patients normalized calprotectin levels (<150 µg/g). Nine of 19 (47.3%) of patients with clinically severe disease (defined by Physician Global Assessment) achieved clinical remission at the end of phase I. Patients with extraintestinal manifestations had statistically lower clinical response rates to the dietary regimen (p = 0.018). Among patients who received CDED + PEN as add-on treatment, a previous successful course of Exclusive Enteral Nutrition was associated with statistically higher clinical remission rates at Week 8 (p = 0.026). Clinical response at Week 4 was an independent predictor of clinical remission and fecal calprotectin normalization at Week 8 (p = 0.002). CONCLUSION: CDED with PEN confirmed its efficacy in a real-life setting, proving to be effective also in refractory patients and those with severe disease. Early clinical response predicts clinical remission at the end of phase 1.

Active microbial ecosystem in Iron-Age tombs of the Etruscan civilization.

Earth's microbial biosphere extends down through the crust and much of the subsurface, including those microbial ecosystems located within cave systems. Here, we elucidate the microbial ecosystems within anthropogenic 'caves'; the Iron-Age, subterranean tombs of central Italy. The interior walls of the rock (calcium-rich macco) were painted ~2500 years ago and are covered with CaCO3 needles (known as moonmilk). The aims of the current study were to: identify biological/geochemical/biophysical determinants of and characterize bacterial communities involved in CaCO3 precipitation; challenge the maxim that biogenic activity necessarily degrades surfaces; locate the bacterial cells that are the source of the CaCO3 precipitate; and gain insight into the kinetics of moonmilk formation. We reveal that this environment hosts communities that consist primarily of bacteria that are mesophilic for temperature and xerotolerance (including Actinobacteria, Bacteroidetes and Proteobacteria); is populated by photosynthetic Cyanobacteria exhibiting heterotrophic nutrition (Calothrix and Chroococcidiopsis); and has CaCO3 precipitating on the rock surfaces (confirmation that this process is biogenic) that acts to preserve rather than damage the painted surface. We also identified that some community members are psychrotolerant (Polaromonas), acidotolerant or acidophilic (members of the Acidobacteria), or resistant to ionizing radiation (Brevundimonas and Truepera); elucidate the ways in which microbiology impacts mineralogy and vice versa; and reveal that biogenic formation of moonmilk can occur rapidly, that is, over a period of 10 to 56 years. We discuss the paradox that these ecosystems, that are for the most part in the dark and lack primary production, are apparently highly active, biodiverse and biomass-rich.

Antifungals, arthropods and antifungal resistance prevention: lessons from ecological interactions.

Arthropods can produce a wide range of antifungal compounds, including specialist proteins, cuticular products, venoms and haemolymphs. In spite of this, many arthropod taxa, particularly eusocial insects, make use of additional antifungal compounds derived from their mutualistic association with microbes. Because multiple taxa have evolved such mutualisms, it must be assumed that, under certain ecological circumstances, natural selection has favoured them over those relying upon endogenous antifungal compound production. Further, such associations have been shown to persist versus specific pathogenic fungal antagonists for more than 50 million years, suggesting that compounds employed have retained efficacy in spite of the pathogens' capacity to develop resistance. We provide a brief overview of antifungal compounds in the arthropods' armoury, proposing a conceptual model to suggest why their use remains so successful. Fundamental concepts embedded within such a model may suggest strategies by which to reduce the rise of antifungal resistance within the clinical milieu.

Rarity of human T helper 17 cells is due to retinoic acid orphan receptor-dependent mechanisms that limit their expansion.

The reason why CD4(+) T helper 17 (Th17) cells, despite their well-known pathogenic role in chronic inflammatory disorders, are very rare in the inflammatory sites remains unclear. We demonstrate that human Th17 cells exhibit low ability to proliferate and to produce the T cell growth factor interleukin-2 (IL-2), in response to combined CD3 and CD28 stimulation. This was due to the upregulated expression of IL-4-induced gene 1 (IL4I1) mRNA, a secreted L-phenylalanine oxidase, which associated with a decrease in CD3ζ chain expression and consequent abnormalities in the molecular pathway that allows IL-2 production and cell proliferation. High IL4I1 mRNA expression was detectable in Th17 cell precursors and was strictly dependent on Th17 cell master gene, the retinoid acid related orphan receptor (RORC). Th17 cells also exhibited RORC-dependent CD28 hyperexpression and the ability to produce IL-17A after CD28 stimulation without CD3 triggering. Our findings suggest that the rarity of human Th17 cells in inflamed tissues results from RORC-dependent mechanisms limiting their expansion.

Gut microbiota profiles and characterization of cultivable fungal isolates in IBS patients.

Studies so far conducted on irritable bowel syndrome (IBS) have been focused mainly on the role of gut bacterial dysbiosis in modulating the intestinal permeability, inflammation, and motility, with consequences on the quality of life. Limited evidences showed a potential involvement of gut fungal communities. Here, the gut bacterial and fungal microbiota of a cohort of IBS patients have been characterized and compared with that of healthy subjects (HS). The IBS microbial community structure differed significantly compared to HS. In particular, we observed an enrichment of bacterial taxa involved in gut inflammation, such as Enterobacteriaceae, Streptococcus, Fusobacteria, Gemella, and Rothia, as well as depletion of health-promoting bacterial genera, such as Roseburia and Faecalibacterium. Gut microbial profiles in IBS patients differed also in accordance with constipation. Sequence analysis of the gut mycobiota showed enrichment of Saccharomycetes in IBS. Culturomics analysis of fungal isolates from feces showed enrichment of Candida spp. displaying from IBS a clonal expansion and a distinct genotypic profiles and different phenotypical features when compared to HS of Candida albicans isolates. Alongside the well-characterized gut bacterial dysbiosis in IBS, this study shed light on a yet poorly explored fungal component of the intestinal ecosystem, the gut mycobiota. Our results showed a differential fungal community in IBS compared to HS, suggesting potential for new insights on the involvement of the gut mycobiota in IBS. KEY POINTS: • Comparison of gut microbiota and mycobiota between IBS and healthy subjects • Investigation of cultivable fungi in IBS and healthy subjects • Candida albicans isolates result more virulent in IBS subjects compared to healthy subjects.

Propolis hosts a diversemicrobial community.

Despite the deep knowledge of the honey bee (Apis mellifera) gut microbiome, information on the microbial communities of other hive components is still scarce. Propolis originates from a natural resinous mixture that honeybees collect from different plants sources and modify; it is used mainly to ensure the hygiene of the hive. By virtue of its antimicrobial properties, propolis has been considered relatively aseptic, yet its ability to harbor microorganisms has not been previously investigated. In this study we report the first description of the diversity of the microbial community of propolis by both targeted-metagenomics analysis and cultivation. We demonstrated that propolis hosts a variety of microbial strains belonging to taxa already described in other hive components. Some of them are cultivable in standard laboratory conditions, and show metabolic characteristics compatible with their persistence in different physiological states inside propolis. Isolated bacteria produce antimicrobials against Gram-negative and Gram-positive bacteria, and entomopathogenic fungi, with different spectra of inhibition. Metagenomics analysis shows the presence of bacteria and fungi with great potential to outcompete potentially harmful microorganisms. These findings suggest that the characterized microbiota could contribute to the overall antimicrobial properties of propolis and to its ecological role as "disinfectant" within the hive.

Population genomics reveals evolution and variation of Saccharomyces cerevisiae in the human and insects gut.

The quest to discover the variety of ecological niches inhabited by Saccharomyces cerevisiae has led to research in areas as diverse as wineries, oak trees and insect guts. The discovery of fungal communities in the human gastrointestinal tract suggested the host's gut as a potential reservoir for yeast adaptation. Here, we report the existence of yeast populations associated with the human gut (HG) that differ from those isolated from other human body sites. Phylogenetic analysis on 12 microsatellite loci and 1715 combined CDSs from whole-genome sequencing revealed three subclusters of HG strains with further evidence of clonal colonization within the host's gut. The presence of such subclusters was supported by other genomic features, such as copy number variation, absence/introgressions of CDSs and relative polymorphism frequency. Functional analysis of CDSs specific of the different subclusters suggested possible alterations in cell wall composition and sporulation features. The phenotypic analysis combined with immunological profiling of these strains further showed that sporulation was related with strain-specific genomic characteristics in the immune recognition pattern. We conclude that both genetic and environmental factors involved in cell wall remodelling and sporulation are the main drivers of adaptation in S. cerevisiae populations in the human gut.

Environmental pollution effects on plant microbiota: the case study of poplar bacterial-fungal response to silver nanoparticles.

Pollution affects most of the urban and forest environments at different levels causing well-known effects on human and plant health. The influence that pollutants exert on plant-associated microbiota might direct plant health and, in some cases, also the removal of pollutants by plants. With the advent of nanotechnologies, an increasing amount of engineered nanoparticles are being introduced into the environment, and consequently, their impact on plant-associated microorganisms needs to be investigated. In this context, silver nanoparticles (Ag-NPs) were experimentally supplied at leaf and root level of poplar plants to assess Ag-NPs effects on plant microbiota. Leaf Ag-NP treatment increased bacteria and fungi evenness and determined a significant reduction in both microbial groups, while root Ag-NP treatment reduced the bacterial and fungal biodiversity. Bioinformatics functional analysis showed that Ag-NP treatment reduced the aerobic and stimulated facultative anaerobic and oxidative stress-tolerant bacteria. Our study offers new insights into the effects of Ag-NPs on both phyllosphere and rhizosphere poplar-associated microbiota and may represent a first attempt to understand the behavior of microbial communities of a tree species growing in a polluted environment.

Social wasps are a Saccharomyces mating nest.

The reproductive ecology of Saccharomyces cerevisiae is still largely unknown. Recent evidence of interspecific hybridization, high levels of strain heterozygosity, and prion transmission suggest that outbreeding occurs frequently in yeasts. Nevertheless, the place where yeasts mate and recombine in the wild has not been identified. We found that the intestine of social wasps hosts highly outbred S. cerevisiae strains as well as a rare S. cerevisiae×S. paradoxus hybrid. We show that the intestine of Polistes dominula social wasps favors the mating of S. cerevisiae strains among themselves and with S. paradoxus cells by providing a succession of environmental conditions prompting cell sporulation and spores germination. In addition, we prove that heterospecific mating is the only option for European S. paradoxus strains to survive in the gut. Taken together, these findings unveil the best hidden secret of yeast ecology, introducing the insect gut as an environmental alcove in which crosses occur, maintaining and generating the diversity of the ascomycetes.

Pathway Inspector: a pathway based web application for RNAseq analysis of model and non-model organisms.

SUMMARY: Pathway Inspector is an easy-to-use web application helping researchers to find patterns of expression in complex RNAseq experiments. The tool combines two standard approaches for RNAseq analysis: the identification of differentially expressed genes and a topology-based analysis of enriched pathways. Pathway Inspector is equipped with ad hoc interactive graphical interfaces simplifying the discovery of modulated pathways and the integration of the differentially expressed genes in the corresponding pathway topology. AVAILABILITY AND IMPLEMENTATION: Pathway Inspector is available at the website http://admiral.fmach.it/PI and has been developed in Python, making use of the Django Web Framework. CONTACT: Contact:paolo.fontana@fmach.it

Bifidobacterium callitrichidarum sp. nov. from the faeces of the emperor tamarin (Saguinus imperator).

Three Gram-stain-positive, non-spore-forming, microaerophilic and fructose-6-phosphate phosphoketolase positive strains were isolated from a faecal sample of an adult subject of the emperor tamarin (Saguinus imperator). Given that the isolates revealed identical BOX PCR profiles, strain TRI 5T was selected as a representative and characterized further. Comparative analysis of 16S rRNA gene sequence similarity revealed that strain TRI 5T was closely related to Bifidobacterium saguini DSM 23967T (96.4 %) and to Bifidobacterium longum subsp. longum ATCC 15708 (96.2 %). Multilocus sequence analyses of five housekeeping genes showed the close phylogenetic relatedness of this strain to Bifidobacterium breve DSM 20213T (hsp60 94.1 %), Bifidobacterium saguini DSM 23967T (clpC 91 %), Bifidobacterium avesanii DSM 100685T (dnaG 80.3 %), Bifidobacterium longumsubsp. infantis ATCC 15697T (dnaJ 85.3 %) and Bifidobacterium longumsubsp. longum ATCC 15708 (rpoB 93 %), respectively. The peptidoglycan type was A3ß, with an interpeptide bridge comprising l-Orn (Lys) - l-Ser - l-Ala - l-Thr - l-Ala. The DNA G+C content of strain TRI 5T was 60.9 mol%. Based on the data provided, strain TRI 5T represents a novel species of the genus Bifidobacterium for which the name Bifidobacteriumcallitrichidarum sp. nov. is proposed. The type strain is TRI 5T (=DSM 103152T=JCM 31790T).

Intestinal Candida parapsilosis isolates from Rett syndrome subjects bear potential virulent traits and capacity to persist within the host.

BACKGROUND: Rett syndrome (RTT) is a neurological disorder mainly caused by mutations in MeCP2 gene. It has been shown that MeCP2 impairments can lead to cytokine dysregulation due to MeCP2 regulatory role in T-helper and T-reg mediated responses, thus contributing to the pro-inflammatory status associated with RTT. Furthermore, RTT subjects suffer from an intestinal dysbiosis characterized by an abnormal expansion of the Candida population, a known factor responsible for the hyper-activation of pro-inflammatory immune responses. Therefore, we asked whether the intestinal fungal population of RTT subjects might contribute the sub-inflammatory status triggered by MeCP2 deficiency. METHODS: We evaluated the cultivable gut mycobiota from a cohort of 50 RTT patients and 29 healthy controls characterizing the faecal fungal isolates for their virulence-related traits, antifungal resistance and immune reactivity in order to elucidate the role of fungi in RTT's intestinal dysbiosis and gastrointestinal physiology. RESULTS: Candida parapsilosis, the most abundant yeast species in RTT subjects, showed distinct genotypic profiles if compared to healthy controls' isolates as measured by hierarchical clustering analysis from RAPD genotyping. Their phenotypical analysis revealed that RTT's isolates produced more biofilm and were significantly more resistant to azole antifungals compared to the isolates from the healthy controls. In addition, the high levels of IL-1ß and IL-10 produced by peripheral blood mononuclear cells and the mixed Th1/Th17 cells population induced by RTT C. parapsilosis isolates suggest the capacity of these intestinal fungi to persist within the host, being potentially involved in chronic, pro-inflammatory responses. CONCLUSIONS: Here we demonstrated that intestinal C. parapsilosis isolates from RTT subjects hold phenotypic traits that might favour the previously observed low-grade intestinal inflammatory status associated with RTT. Therefore, the presence of putative virulent, pro-inflammatory C. parapsilosis strains in RTT could represent an additional factor in RTT's gastrointestinal pathophysiology, whose mechanisms are not yet clearly understood.

Fungal Chitin Induces Trained Immunity in Human Monocytes during Cross-talk of the Host with Saccharomyces cerevisiae.

The immune system is essential to maintain the mutualistic homeostatic interaction between the host and its micro- and mycobiota. Living as a commensal,Saccharomyces cerevisiaecould potentially shape the immune response in a significant way. We observed thatS. cerevisiaecells induce trained immunity in monocytes in a strain-dependent manner through enhanced TNFα and IL-6 production upon secondary stimulation with TLR ligands, as well as bacterial and fungal commensals. Differential chitin content accounts for the differences in training properties observed among strains, driving induction of trained immunity by increasing cytokine production and direct antimicrobial activity bothin vitroandin vivo These chitin-induced protective properties are intimately associated with its internalization, identifying a critical role of phagosome acidification to facilitate microbial digestion. This study reveals how commensal and passenger microorganisms could be important in promoting health and preventing mucosal diseases by modulating host defense toward pathogens and thus influencing the host microbiota-immune system interactions.

The orphan nuclear receptor COUP-TFII coordinates hypoxia-independent proangiogenic responses in hepatic stellate cells.

BACKGROUND & AIMS: Hepatic stellate cell (HSC) transdifferentiation into collagen-producing myofibroblasts is a key event in hepatic fibrogenesis, but the transcriptional network that controls the acquisition of the activated phenotype is still poorly understood. In this study, we explored whether the nuclear receptor chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) is involved in HSC activation and in the multifunctional role of these cells during the response to liver injury. METHODS: COUP-TFII expression was evaluated in normal and cirrhotic livers by immunohistochemistry and Western blot. The role of COUP-TFII in HSC was assessed by gain and loss of function transfection experiments and by generation of mice with COUP-TFII deletion in HSC. Molecular changes were determined by gene expression microarray and RT-qPCR. RESULTS: We showed that COUP-TFII is highly expressed in human fibrotic liver and in mouse models of hepatic injury. COUP-TFII expression rapidly increased upon HSC activation and it was associated with the regulation of genes involved in cell motility, proliferation and angiogenesis. Inactivation of COUP-TFII impairs proliferation and invasiveness in activated HSC and COUP-TFII deletion in mice abrogate HSC activation and angiogenesis. Finally, co-culture experiments with HSC and liver sinusoidal endothelial cells (SEC) showed that COUP-TFII expression in HSC influenced SEC migration and tubulogenesis via a hypoxia-independent and nuclear factor kappaB-dependent mechanism. CONCLUSION: This study elucidates a novel transcriptional pathway in HSC that is involved in the acquisition of the proangiogenic phenotype and regulates the paracrine signals between HSC and SEC during hepatic wound healing. LAY SUMMARY: In this study, we identified an important regulator of HSC pathobiology. We showed that the orphan receptor COUP-TFII is an important player in hepatic neoangiogenesis. COUP-TFII expression in HSC controls the crosstalk between HSC and endothelial cells coordinating vascular remodelling during liver injury. TRANSCRIPT PROFILING: ArrayExpress accession E-MTAB-1795.

Social wasp intestines host the local phenotypic variability of Saccharomyces cerevisiae strains.

Nowadays, the presence of Saccharomyces cerevisiae has been assessed in both wild and human-related environments. Social wasps have been shown to maintain and vector S. cerevisiae among different environments. The availability of strains isolated from wasp intestines represents a striking opportunity to assess whether the strains found in wasp intestines are characterized by peculiar traits. We analysed strains isolated from the intestines of social wasps and compared them with strains isolated from other sources, all collected in a restricted geographic area. We evaluated the production of volatile metabolites during grape must fermentation, the resistance to different stresses and the ability to exploit various carbon sources. Wasp strains, in addition to representing a wide range of S. cerevisiae genotypes, also represent large part of the phenotypes characterizing the sympatric set of yeast strains; their higher production of acetic acid and ethyl acetate could reflect improved ability to attract insects. Our findings suggest that the relationship between yeasts and wasps should be preserved, to safeguard not only the natural variance of this microorganism but also the interests of wine-makers, who could take advantage from the exploitation of their phenotypic variability. Copyright © 2016 John Wiley & Sons, Ltd.

Explaining diversity in metagenomic datasets by phylogenetic-based feature weighting.

Metagenomics is revolutionizing our understanding of microbial communities, showing that their structure and composition have profound effects on the ecosystem and in a variety of health and disease conditions. Despite the flourishing of new analysis methods, current approaches based on statistical comparisons between high-level taxonomic classes often fail to identify the microbial taxa that are differentially distributed between sets of samples, since in many cases the taxonomic schema do not allow an adequate description of the structure of the microbiota. This constitutes a severe limitation to the use of metagenomic data in therapeutic and diagnostic applications. To provide a more robust statistical framework, we introduce a class of feature-weighting algorithms that discriminate the taxa responsible for the classification of metagenomic samples. The method unambiguously groups the relevant taxa into clades without relying on pre-defined taxonomic categories, thus including in the analysis also those sequences for which a taxonomic classification is difficult. The phylogenetic clades are weighted and ranked according to their abundance measuring their contribution to the differentiation of the classes of samples, and a criterion is provided to define a reduced set of most relevant clades. Applying the method to public datasets, we show that the data-driven definition of relevant phylogenetic clades accomplished by our ranking strategy identifies features in the samples that are lost if phylogenetic relationships are not considered, improving our ability to mine metagenomic datasets. Comparison with supervised classification methods currently used in metagenomic data analysis highlights the advantages of using phylogenetic information.

Reversion of a fungal genetic code alteration links proteome instability with genomic and phenotypic diversification.

Many fungi restructured their proteomes through incorporation of serine (Ser) at thousands of protein sites coded by the leucine (Leu) CUG codon. How these fungi survived this potentially lethal genetic code alteration and its relevance for their biology are not understood. Interestingly, the human pathogen Candida albicans maintains variable Ser and Leu incorporation levels at CUG sites, suggesting that this atypical codon assignment flexibility provided an effective mechanism to alter the genetic code. To test this hypothesis, we have engineered C. albicans strains to misincorporate increasing levels of Leu at protein CUG sites. Tolerance to the misincorporations was very high, and one strain accommodated the complete reversion of CUG identity from Ser back to Leu. Increasing levels of Leu misincorporation decreased growth rate, but production of phenotypic diversity on a phenotypic array probing various metabolic networks, drug resistance, and host immune cell responses was impressive. Genome resequencing revealed an increasing number of genotype changes at polymorphic sites compared with the control strain, and 80% of Leu misincorporation resulted in complete loss of heterozygosity in a large region of chromosome V. The data unveil unanticipated links between gene translational fidelity, proteome instability and variability, genome diversification, and adaptive phenotypic diversity. They also explain the high heterozygosity of the C. albicans genome and open the door to produce microorganisms with genetic code alterations for basic and applied research.

Hsp12p and PAU genes are involved in ecological interactions between natural yeast strains.

The coexistence of different yeasts in a single vineyard raises the question on how they communicate and why slow growers are not competed out. Genetically modified laboratory strains of Saccharomyces cerevisiae are extensively used to investigate ecological interactions, but little is known about the genes regulating cooperation and competition in ecologically relevant settings. Here, we present evidences of Hsp12p-dependent altruistic and contact-dependent competitive interactions between two natural yeast isolates. Hsp12p is released during cell death for public benefit by a fast-growing strain that also produces a killer toxin to inhibit growth of a slow grower that can enjoy the benefits of released Hsp12p. We also show that the protein Pau5p is essential in the defense against the killer effect. Our results demonstrate that the combined action of Hsp12p, Pau5p and a killer toxin is sufficient to steer a yeast community.

Richness and diversity of mammalian fungal communities shape innate and adaptive immunity in health and disease.

Human holobiomes are networks of mutualistic interactions between human cells and complex communities of bacteria and fungi that colonize the human body. The immune system must tolerate colonization with commensal bacteria and fungi but defend against invasion by either organism. Molecular ecological surveys of the human prokaryotic microbiota performed to date have revealed a remarkable degree of bacterial diversity and functionality. However, there is a dearth of information regarding the eukaryotic composition of the microbiota. In this review, we describe the ecology and the human niches of our fungal "fellow travelers" in both health and disease, discriminating between passengers, colonizers, and pathogens based on the interaction of these fungi with the human immune system. We conclude by highlighting the need to reconsider the etiology of many fungal and immune-related diseases in the context of the crosstalk between the human system and its resident microbial communities.

IL-4-induced gene 1 maintains high Tob1 expression that contributes to TCR unresponsiveness in human T helper 17 cells.

Human Th17 cells have a limited proliferative capacity compared to other T-cell subsets. We have shown that human Th17 cells display impaired IL-2 production due to IL-4-induced gene 1 (IL4I1) upregulation. Here, we show that in human Th17 cells, IL4I1 also maintains high levels of Tob1, a member of the Tob/BTG (B-cell traslocation gene) antiproliferative protein family, which prevents cell-cycle progression mediated by TCR stimulation. Indeed, Th17 cells exhibited higher levels of Tob1 than Th1 cells in both resting and TCR-activated conditions. Accordingly, the expression of positive regulators of the cell cycle (cyclin A, B, C, and E and Cdk2), as well as of Skp2, which promotes Tob1 degradation, was lower in Th17 cells than in Th1 cells. Tob1 expression in human Th17 cells correlated with both RAR (retinoic acid receptor)-related orphan receptor C (RORC) and IL4I1 levels. However, RORC was not directly involved in the regulation of Tob1 expression, whereas IL4I1 silencing in Th17 cells induced a substantial decrease of Tob1 expression. These data suggest that IL4I1 upregulation in human Th17 cells limits their TCR-mediated expansion not only by blocking the molecular pathway involved in the activation of the IL-2 promoter, but also by maintaining high levels of Tob1, which impairs entry into the cell cycle.