Management of Autoimmune Encephalitis in a 7-Year-Old Child With CTLA-4 Haploinsufficiency and AMPA Receptor Antibodies: A Case Report.

OBJECTIVES: We report on the therapeutic management of early-onset severe neurologic symptoms in cytotoxic T lymphocyte antigen-4 haploinsufficiency (CTLA-4h) and the presence of antibodies to the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) as an important finding. METHODS: This is a case report from a Dutch academic hospital. Repeated clinical examinations, repeated brain MRI and extended diagnostics on serum and CSF were performed. We used the CARE checklist. RESULTS: A 7-year-old boy was diagnosed with CTLA-4h based on family screening. On diagnosis, he had mild chronic diarrhea and autism spectrum disorder, but no abnormalities in extensive laboratory screening. Six months later, he presented with sudden-onset autoimmune encephalitis. Repeated brain MRI revealed no abnormalities, but immunohistochemistry analysis on serum and CSF showed the presence of AMPAR antibodies. Treatment was initially focused on immunomodulation and targeted CTLA-4 replacement therapy. Because of the persistent fluctuating cerebellar and neuropsychiatric symptoms and the potential clinical significance of the AMPAR antibodies, treatment was intensified with repetition of first-line immunomodulation and rituximab. This combined therapy resulted in sustained clinical improvement and served as a bridge to curative hematopoietic stem cell transplantation. DISCUSSION: This case illustrates the rare early onset of autoimmune encephalitis and presence of AMPAR antibodies in CTLA-4h. Targeted CTLA-4 replacement therapy resulted in a partial response. However, awaiting its optimal therapeutic effect, refractory CNS symptoms required intensification of immunomodulation. The identification of AMPAR antibodies guided our treatment decisions. CLASSIFICATION OF EVIDENCE: This provides Class IV evidence. It is a single observational study without controls.

Serum Immune Profiling in Paediatric Crohn's Disease Demonstrates Stronger Immune Modulation With First-Line Infliximab Than Conventional Therapy and Pre-Treatment Profiles Predict Clinical Response to Both Treatments.

BACKGROUND: Despite its efficacy, rational guidance for starting/stopping first-line biologic treatment in individual paediatric Crohn's disease [CD] patients is needed. We assessed how serum immune profiles before and after first-line infliximab [FL-IFX] or conventional [CONV] induction therapy associate with disease remission at week 52. METHODS: Pre- [n = 86], and 10-14-week post-treatment [n = 84] sera were collected from patients with moderate-to-severe paediatric CD in the TISKids trial, randomized to FL-IFX [n = 48; five 5-mg/kg infusions over 22 weeks] or CONV [n = 43; exclusive enteral nutrition or oral prednisolone]; both groups received azathioprine maintenance. The relative concentrations of 92 inflammatory proteins were determined with Olink Proteomics; fold changes [FC] with |log2FC| > 0.5 after false discovery rate adjustment were considered significant. RESULTS: FL-IFX modulated a larger number of inflammatory proteins and induced stronger suppression than CONV; 18/30 proteins modulated by FL-IFX were not regulated by CONV. Hierarchical clustering based on IFX-modulated proteins at baseline revealed two clusters of patients: CD-hi patients had significantly higher concentrations of 23/30 IFX-modulated proteins [including oncostatin-M, TNFSF14, HGF and TGF-α], and higher clinical disease activity, C-reactive protein and blood neutrophils at baseline than CD-lo patients. Only 24% of CD-hi FL-IFX-treated patients maintained remission without escalation at week 52 vs 58% of CD-lo FL-IFX-treated patients. Similarly, 6% of CD-hi CONV-treated patients achieved remission vs 20% of CONV-treated CD-lo patients. Clustering based on immune profiles post-induction therapy did not relate to remission at week 52. CONCLUSION: FL-IFX leads to stronger reductions and modulates more immune proteins than CONV. Stratification on pre-treatment profiles of IFX-modulated proteins directly relates to maintenance of remission without treatment escalation. TRIAL REGISTRATION NUMBER: NCT02517684.

Endogenous secretory leukocyte protease inhibitor inhibits microbial-induced monocyte activation.

In the intestine, epithelial factors condition incoming immune cells including monocytes to adapt their threshold of activation and prevent undesired inflammation. Colonic epithelial cells express Secretory Leukocyte Protease Inhibitor (SLPI), an inhibitor of NF kappa light chain enhancer of activated B cells (NF-κB) that mediates epithelial hyporesponsiveness to microbial stimuli. Uptake of extracellular SLPI by monocytes has been proposed to inhibit monocyte activation. We questioned whether monocytes can produce SLPI and whether endogenous SLPI can inhibit monocyte activation. We demonstrate that human THP-1 monocytic cells produce SLPI and that CD68+ SLPI-producing cells can be detected in human intestinal lamina propria. Knockdown of SLPI in human THP-1 cells significantly increased NF-κB activation and subsequent C-X-C motif chemokine ligand 8 (CXCL8) and TNF-α production in response to microbial stimulation. Reconstitution of SLPI-deficient cells with either full-length SLPI or SLPI lacking its signal peptide rescued inhibition of NF-κB activation and cytokine production, demonstrating that endogenous SLPI inhibits monocytic cell activation. Unexpectedly, exogenous SLPI did not inhibit CXCL8 or TNF-α production, despite efficient uptake. Our data argue that endogenous SLPI can regulate the threshold of activation in monocytes, thereby preventing activation by commensal bacteria in mucosal tissues.

Proteomic analyses do not reveal subclinical inflammation in fatigued patients with clinically quiescent inflammatory bowel disease.

Fatigue is a common and clinically challenging symptom in patients with inflammatory bowel diseases (IBD), occurring in ~ 50% of patients with quiescent disease. In this study, we aimed to investigate whether fatigue in patients with clinically quiescent IBD is reflected by circulating inflammatory proteins, which might reflect ongoing subclinical inflammation. Ninety-two (92) different inflammation-related proteins were measured in plasma of 350 patients with clinically quiescent IBD. Quiescent IBD was defined as clinical (Harvey-Bradshaw Index < 5 or Simple Clinical Colitis Activity Index < 2.5) and biochemical remission (C-reactive protein < 5 mg/L and absence of anemia) at time of fatigue assessment. Leukemia inhibitory factor receptor (LIF-R) concentrations were inversely associated with severe fatigue, also after adjustment for confounding factors (nominal P < 0.05). Although solely LIF-R showed weak ability to discriminate between mild and severe fatigue (area under the curve [AUC] = 0.61, 95%CI: 0.53-0.69, P < 0.05), a combined set of the top seven (7) fatigue-associated proteins (all P < 0.10) was observed to have reasonable discriminative performance (AUC = 0.82 [95%CI: 0.74-0.91], P < 0.01). Fatigue in patients with IBD is not clearly reflected by distinct protein signatures, suggesting there is no subclinical inflammation defined by the studied inflammatory proteins. Future studies are warranted to investigate other proteomic markers that may reflect fatigue in clinically quiescent IBD.

High expression of secretory leukocyte protease inhibitor (SLPI) in stage III micro-satellite stable colorectal cancer is associated with reduced disease recurrence.

Secretory leukocyte protease inhibitor (SLPI) is a pleiotropic protein produced by healthy intestinal epithelial cells. SLPI regulates NF-κB activation, inhibits neutrophil proteases and has broad antimicrobial activity. Recently, increased SLPI expression was found in various types of carcinomas and was suggested to increase their metastatic potential. Indeed, we demonstrated that SLPI protein expression in colorectal cancer (CRC) liver metastases and matched primary tumors is associated with worse outcome, suggesting that SLPI promotes metastasis in human CRC. However, whether SLPI plays a role in CRC before distant metastases have formed is unclear. Therefore, we examined whether SLPI expression is associated with prognosis in CRC patients with localized disease. Using a cohort of 226 stage II and 160 stage III CRC patients we demonstrate that high SLPI protein expression is associated with reduced disease recurrence in patients with stage III micro-satellite stable tumors treated with adjuvant chemotherapy, independently of established clinical risk factors (hazard rate ratio 0.54, P-value 0.03). SLPI protein expression was not associated with disease-free survival in stage II CRC patients. Our data suggest that the role of SLPI in CRC may be different depending on the stage of disease. In stage III CRC, SLPI expression may be unfavorable for tumors, whereas SLPI expression may be beneficial for tumors once distant metastases have established.

Long-Term Dietary Patterns Are Reflected in the Plasma Inflammatory Proteome of Patients with Inflammatory Bowel Disease.

Diet plays an important role in the development and progression of inflammatory bowel disease (IBD, comprising Crohn's disease (CD) and ulcerative colitis (UC)). However, little is known about the extent to which different diets reflect inflammation in IBD beyond measures such as faecal calprotectin or C-reactive protein. In this study, we aimed to unravel associations between dietary patterns and circulating inflammatory proteins in patients with IBD. Plasma concentrations of 73 different inflammation-related proteins were measured in 454 patients with IBD by proximity extension assay (PEA) technology. Food frequency questionnaires (FFQ) were used to assess habitual diet. Principal component analysis (PCA) was performed to extract data-driven dietary patterns. To identify associations between dietary patterns and plasma proteins, we used general linear models adjusting for age, sex, BMI, plasma storage time, smoking, surgical history and medication use. Stratified analyses were performed for IBD type, disease activity and protein intake. A high-sugar diet was strongly inversely associated with fibroblast growth factor-19 (FGF-19) independent of IBD type, disease activity, surgical history and deviance from recommended protein intake (false discovery rate (FDR) < 0.05). Conversely, a Mediterranean-style pattern was associated with higher FGF-19 levels (FDR < 0.05). A pattern characterised by high alcohol and coffee intake was positively associated with CCL11 (eotaxin-1) levels and with lower levels of IL-12B (FDR < 0.05). All results were replicated in CD, whereas only the association with FGF-19 was significant in UC. Our study suggests that dietary habits influence distinct circulating inflammatory proteins implicated in IBD and supports the pro- and anti-inflammatory role of diet. Longitudinal measurements of inflammatory markers, also postprandial, are needed to further elucidate the diet−inflammation relationship.

First-line treatment with infliximab versus conventional treatment in children with newly diagnosed moderate-to-severe Crohn's disease: an open-label multicentre randomised controlled trial.

OBJECTIVE: In newly diagnosed paediatric patients with moderate-to-severe Crohn's disease (CD), infliximab (IFX) is initiated once exclusive enteral nutrition (EEN), corticosteroid and immunomodulator therapies have failed. We aimed to investigate whether starting first-line IFX (FL-IFX) is more effective to achieve and maintain remission than conventional treatment. DESIGN: In this multicentre open-label randomised controlled trial, untreated patients with a new diagnosis of CD (3-17 years old, weighted Paediatric CD Activity Index score (wPCDAI) >40) were assigned to groups that received five infusions of 5 mg/kg IFX at weeks 0, 2, 6, 14 and 22 (FL-IFX), or EEN or oral prednisolone (1 mg/kg, maximum 40 mg) (conventional). The primary outcome was clinical remission on azathioprine, defined as a wPCDAI <12.5 at week 52, without need for treatment escalation, using intention-to-treat analysis. RESULTS: 100 patients were included, 50 in the FL-IFX group and 50 in the conventional group. Four patients did not receive treatment as per protocol. At week 10, a higher proportion of patients in the FL-IFX group than in the conventional group achieved clinical (59% vs 34%, respectively, p=0.021) and endoscopic remission (59% vs 17%, respectively, p=0.001). At week 52, the proportion of patients in clinical remission was not significantly different (p=0.421). However, 19/46 (41%) patients in the FL-IFX group were in clinical remission on azathioprine monotherapy without need for treatment escalation vs 7/48 (15%) in the conventional group (p=0.004). CONCLUSIONS: FL-IFX was superior to conventional treatment in achieving short-term clinical and endoscopic remission, and had greater likelihood of maintaining clinical remission at week 52 on azathioprine monotherapy. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Registry (NCT02517684).

Secretory Leukocyte Protease Inhibitor (SLPI) in mucosal tissues: Protects against inflammation, but promotes cancer.

The immune system is continuously challenged with large quantities of exogenous antigens at the barriers between the external environment and internal human tissues. Antimicrobial activity is essential at these sites, though the immune responses must be tightly regulated to prevent tissue destruction by inflammation. Secretory Leukocyte Protease Inhibitor (SLPI) is an evolutionarily conserved, pleiotropic protein expressed at mucosal surfaces, mainly by epithelial cells. SLPI inhibits proteases, exerts antimicrobial activity and inhibits nuclear factor-kappa B (NF-κB)-mediated inflammatory gene transcription. SLPI maintains homeostasis at barrier tissues by preventing tissue destruction and regulating the threshold of inflammatory immune responses, while protecting the host from infection. However, excessive expression of SLPI in cancer cells may have detrimental consequences, as recent studies demonstrate that overexpression of SLPI increases the metastatic potential of epithelial tumors. Here, we review the varied functions of SLPI in the respiratory tract, skin, gastrointestinal tract and genitourinary tract, and then discuss the mechanisms by which SLPI may contribute to cancer.

Expression of the immune modulator secretory leukocyte protease inhibitor (SLPI) in colorectal cancer liver metastases and matched primary tumors is associated with a poorer prognosis.

Secretory leukocyte protease inhibitor (SLPI), a pleiotropic protein expressed by healthy intestinal epithelial cells, functions as an inhibitor of NF-κB and neutrophil proteases and exerts antimicrobial activity. We previously showed SLPI suppresses intestinal epithelial chemokine production in response to microbial contact. Increased SLPI expression was recently detected in various types of carcinoma. In addition, accumulating evidence indicates SLPI expression is favorable for tumor cells. In view of these findings and the abundance of SLPI in the colonic epithelium, we hypothesized SLPI promotes colorectal cancer (CRC) growth and metastasis. Here, we aimed to establish whether SLPI expression in CRC is related to clinical outcome. Using a cohort of 507 patients with CRC who underwent resection of liver metastases, we show that high SLPI protein expression in both liver metastases and primary CRC is associated with significantly shorter overall survival after resection of liver metastases. The prognostic value of SLPI in CRC patients with liver metastases implies a role for SLPI in the formation of metastasis of human CRC. Based on the immune regulatory functions of SLPI, we anticipate that expression of SLPI provides tumors with a mechanism to evade infiltration by immune cells.

International prospective observational study investigating the disease course and heterogeneity of paediatric-onset inflammatory bowel disease: the protocol of the PIBD-SETQuality inception cohort study.

INTRODUCTION: Patients with paediatric-onset inflammatory bowel disease (PIBD) may develop a complicated disease course, including growth failure, bowel resection at young age and treatment-related adverse events, all of which can have significant and lasting effects on the patient's development and quality of life. Unfortunately, we are still not able to fully explain the heterogeneity between patients and their disease course and predict which patients will respond to certain therapies or are most at risk of developing a more complicated disease course. To investigate this, large prospective studies with long-term follow-up are needed. Currently, no such European or Asian international cohorts exist. In this international cohort, we aim to evaluate disease course and which patients are most at risk of therapy non-response or development of complicated disease based on patient and disease characteristics, immune pathology and environmental and socioeconomic factors. METHODS AND ANALYSIS: In this international prospective observational study, which is part of the PIBD Network for Safety, Efficacy, Treatment and Quality improvement of care (PIBD-SETQuality), children diagnosed with inflammatory bowel disease <18 years are included at diagnosis. The follow-up schedule is in line with standard PIBD care and is intended to continue up to 20 years. Patient and disease characteristics, as well as results of investigations, are collected at baseline and during follow-up. In addition, environmental factors are being assessed (eg, parent's smoking behaviour, dietary factors and antibiotic use). In specific centres with the ability to perform extensive immunological analyses, blood samples and intestinal biopsies are being collected and analysed (flow cytometry, plasma proteomics, mRNA expression and immunohistochemistry) in therapy-naïve patients and during follow-up. ETHICS AND DISSEMINATION: Medical ethical approval has been obtained prior to patient recruitment for all sites. The results will be disseminated through peer-reviewed scientific publications. TRIAL REGISTRATION NUMBER: NCT03571373.

A Comprehensive Analysis of Ontogeny of Renal Drug Transporters: mRNA Analyses, Quantitative Proteomics, and Localization.

Human renal membrane transporters play key roles in the disposition of renally cleared drugs and endogenous substrates, but their ontogeny is largely unknown. Using 184 human postmortem frozen renal cortical tissues (preterm newborns to adults) and a subset of 62 tissue samples, we measured the mRNA levels of 11 renal transporters and the transcription factor pregnane X receptor (PXR) with quantitative real-time polymerase chain reaction, and protein abundance of nine transporters using liquid chromatography tandem mass spectrometry selective reaction monitoring, respectively. Expression levels of p-glycoprotein, urate transporter 1, organic anion transporter 1, organic anion transporter 3, and organic cation transporter 2 increased with age. Protein levels of multidrug and toxin extrusion transporter 2-K and breast cancer resistance protein showed no difference from newborns to adults, despite age-related changes in mRNA expression. Multidrug and toxin extrusion transporter 1, glucose transporter 2, multidrug resistance-associated protein 2, multidrug resistance-associated protein 4 (MRP4), and PXR expression levels were stable. Using immunohistochemistry, we found that MRP4 localization in pediatric samples was similar to that in adult samples. Collectively, our study revealed that renal drug transporters exhibited different rates and patterns of maturation, suggesting that renal handling of substrates may change with age.

Tipping the balance: inhibitory checkpoints in intestinal homeostasis.

The small intestinal and colonic lamina propria are populated with forkhead box P3 (FOXP3)+CD4+ regulatory T cells (Tregs) and interleukin-10-producing T cells that orchestrate intestinal tolerance to harmless microbial and food antigens. Expression of co-inhibitory receptors such as CTLA-4 and PD-1 serve as checkpoints to these cells controlling their T-cell receptor (TCR)-mediated and CD28-mediated activation and modulating the phenotype of neighboring antigen presenting cells. Recent discoveries on the diversity of co-inhibitory receptors and their selective cellular expression has shed new light on their tissue-dependent function. In this review, we provide an overview of the co-inhibitory pathways and checkpoints of Treg and effector T cells and their mechanisms of action in intestinal homeostasis. Better understanding of these inhibitory checkpoints is desired as their blockade harbors clinical potential for the treatment of cancer and their stimulation may offer new opportunities to treat chronic intestinal inflammation such as inflammatory bowel disease.

Frequencies of circulating regulatory TIGIT+CD38+ effector T cells correlate with the course of inflammatory bowel disease.

Disease heterogeneity hampers achieving long-term disease remission in inflammatory bowel disease (IBD). Monitoring ongoing tissue-localized regulatory and inflammatory T-cell responses in peripheral blood would empower disease classification. We determined whether regulatory and inflammatory phenotypes of circulating CD38+ effector (CD62LnegCD4+) T cells, a population enriched for cells with mucosal antigen specificity, classify disease course in pediatric IBD patients. In healthy individuals, circulating CD38+ effector T cells had a predominant regulatory component with lower frequencies of IFNγ-secreting T cells, higher frequencies of IL-10-secreting T cells and higher frequencies of inhibitory molecule T-cell immunoglobulin and ITIM domain+ (TIGIT) cells than CD38neg effector T cells. TIGIT expression was stable upon stimulation and marked CD38+ T cells with inhibitory properties. In IBD patients with active intestinal inflammation this predominant regulatory component was lost: circulating CD38+ effector T cells had increased activated CD25+CD45RAneg and decreased TIGIT+ cell frequencies. TIGIT percentages below 25% before treatment associated with shorter duration of clinical remission. In conclusion, phenotypic changes in circulating CD38+ effector T cells, in particular the frequency of TIGIT+ cells, classify pediatric IBD patients and predict severity of disease course. These findings have relevance for IBD and can be exploited in graft-versus-host-disease and checkpoint inhibitor-induced inflammation in cancer.

Ceramides in tracheal aspirates of preterm infants: Marker for bronchopulmonary dysplasia.

BACKGROUND: In an experimental mouse model we showed that ceramides play a role in the pathogenesis of bronchopulmonary dysplasia (BPD) and are a potential target for therapeutic intervention. We investigated whether ceramides are detectable in tracheal aspirates (TAs) of preterm infants and differ between infants with or without BPD. METHODS: Infants born ≤ 32 weeks of gestational age in need of mechanical ventilation in the first week of life were included. TAs were obtained directly after intubation and at day 1, 3, 5, 7, and 14. Ceramide concentrations were measured by tandem mass spectrometry. At 36 weeks postmenstrual age BPD was defined as having had ≥ 28 days supplemental oxygen. RESULTS: 122 infants were included, of which 14 died and 41 developed BPD. All infants showed an increase in ceramides after the first day of intubation. The ceramide profile differed significantly between preterm infants who did and did not develop BPD. However, the ceramide profile had no additional predictive value for BPD development over GA at birth, birth weight and total days of mechanical ventilation. CONCLUSIONS: Ceramides are measurable in TAs of preterm born infants and may be an early marker for BPD development.

Development and Function of Immune Cells in an Adolescent Patient With a Deficiency in the Interleukin-10 Receptor.

OBJECTIVE: Monogenic defects in the interleukin-10 (IL-10) pathway are extremely rare and cause infantile-onset inflammatory bowel disease (IBD)-like pathology. Understanding how immune responses are dysregulated in monogenic IBD-like diseases can provide valuable insight in "classical" IBD pathogenesis. Here, we studied long-term immune cell development and function in an adolescent IL-10 receptor (IL10RA)-deficient patient who presented in infancy with severe colitis and fistulizing perianal disease and is currently treated with immune suppressants. METHODS: Biomaterial was collected from the IL10RA-deficient patient, pediatric patients with IBD, and healthy controls. The frequency and phenotype of immune cells were determined in peripheral blood and intestinal biopsies by flow cytometry and immunohistochemistry. Functional changes in monocyte-derived dendritic cells and T cells were assessed by in vitro activation assays. RESULTS: The IL10RA-deficient immune system developed normally with respect to numbers and phenotype of circulating immune cells. Despite normal co-stimulatory molecule expression, bacterial lipopolysaccharide-stimulated monocyte-derived dendritic cells from the IL10RA-deficient patient released increased amounts of tumor necrosis factor α compared to healthy controls. Upon T-cell receptor ligation, IL10RA-deficient peripheral blood mononuclear cells released increased amounts of T-cell cytokines interferon γ and IL-17 agreeing with high numbers of T-bet and IL-17 cells in intestinal biopsies taken at disease onset. In vitro, the immunosuppressive drug thalidomide used to treat the patient's decreased peripheral blood mononuclear cell-derived tumor necrosis factor production. CONCLUSIONS: With time and during immunosuppressive treatment the IL10RA-deficient immune system develops relatively normally. Upon activation, IL-10 is crucial for controlling excessive inflammatory cytokine release by dendritic cells and preventing interferon γ and IL-17-mediated T-cell responses.

Human Intestinal PEPT1 Transporter Expression and Localization in Preterm and Term Infants.

The intestinal influx oligopeptide transporter peptide transporter 1 (PEPT1) (SLC15A1) is best known for nutrient-derived di- and tripeptide transport. Its role in drug absorption is increasingly recognized. To better understand the disposition of PEPT1 substrate drugs in young infants, we studied intestinal PEPT1 mRNA expression and tissue localization across the pediatric age range. PEPT1 mRNA expression was determined using real-time reverse-transcription polymerase chain reaction in small intestinal tissues collected from surgical procedures (neonates and infants) or biopsies (older children and adolescents). PEPT1 mRNA relative to villin mRNA expression was compared between neonates/infants and older children/adolescents. PEPT1 was visualized in infant tissue using immunohistochemical staining. Other transporters [multidrug resistance protein 1 (MDR1), multidrug resistance-like protein 2 (MRP2), and organic anion transporter polypeptide 2B1 (OATP2B1)] were also stained to describe the localization in relation to PEPT1. Twenty-six intestinal samples (n = 20 neonates/infants, n = 2 pediatric, n = 4 adolescents) were analyzed. The young infant samples were collected at a median (range) gestational age at birth of 29.2 weeks (24.7-40) and postnatal age of 2.4 weeks (0-16.6). The PEPT1 mRNA expression of the neonates/infants was only marginally lower (0.8-fold) than the older children (P < 0.05). Similar and clear apical PEPT1 and MRP2 staining, apical and lateral MDR1 staining, and intraepithelial OATP2B1 staining at the basolateral membrane of the enterocyte were detected in 12 infant and 2 adolescent samples. Although small intestinal PEPT1 expression tended to be lower in neonates than in older children, this difference is small and tissue distribution is similar. This finding suggests similar oral absorption of PEPT1 substrates across the pediatric age range.

Sialic acid-modified antigens impose tolerance via inhibition of T-cell proliferation and de novo induction of regulatory T cells.

Sialic acids are negatively charged nine-carbon carboxylated monosaccharides that often cap glycans on glycosylated proteins and lipids. Because of their strategic location at the cell surface, sialic acids contribute to interactions that are critical for immune homeostasis via interactions with sialic acid-binding Ig-type lectins (siglecs). In particular, these interactions may be of importance in cases where sialic acids may be overexpressed, such as on certain pathogens and tumors. We now demonstrate that modification of antigens with sialic acids (Sia-antigens) regulates the generation of antigen-specific regulatory T (Treg) cells via dendritic cells (DCs). Additionally, DCs that take up Sia-antigen prevent formation of effector CD4(+) and CD8(+)T cells. Importantly, the regulatory properties endowed on DCs upon Sia-antigen uptake are antigen-specific: only T cells responsive to the sialylated antigen become tolerized. In vivo, injection of Sia-antigen-loaded DCs increased de novo Treg-cell numbers and dampened effector T-cell expansion and IFN-γ production. The dual tolerogenic features that Sia-antigen imposed on DCs are Siglec-E-mediated and maintained under inflammatory conditions. Moreover, loading DCs with Sia-antigens not only inhibited the function of in vitro-established Th1 and Th17 effector T cells but also significantly dampened ex vivo myelin-reactive T cells, present in the circulation of mice with experimental autoimmune encephalomyelitis. These data indicate that sialic acid-modified antigens instruct DCs in an antigen-specific tolerogenic programming, enhancing Treg cells and reducing the generation and propagation of inflammatory T cells. Our data suggest that sialylation of antigens provides an attractive way to induce antigen-specific immune tolerance.

Type 3 innate lymphoid cells maintain intestinal epithelial stem cells after tissue damage.

Disruption of the intestinal epithelial barrier allows bacterial translocation and predisposes to destructive inflammation. To ensure proper barrier composition, crypt-residing stem cells continuously proliferate and replenish all intestinal epithelial cells within days. As a consequence of this high mitotic activity, mucosal surfaces are frequently targeted by anticancer therapies, leading to dose-limiting side effects. The cellular mechanisms that control tissue protection and mucosal healing in response to intestinal damage remain poorly understood. Type 3 innate lymphoid cells (ILC3s) are regulators of homeostasis and tissue responses to infection at mucosal surfaces. We now demonstrate that ILC3s are required for epithelial activation and proliferation in response to small intestinal tissue damage induced by the chemotherapeutic agent methotrexate. Multiple subsets of ILC3s are activated after intestinal tissue damage, and in the absence of ILC3s, epithelial activation is lost, correlating with increased pathology and severe damage to the intestinal crypts. Using ILC3-deficient Lgr5 reporter mice, we show that maintenance of intestinal stem cells after damage is severely impaired in the absence of ILC3s or the ILC3 signature cytokine IL-22. These data unveil a novel function of ILC3s in limiting tissue damage by preserving tissue-specific stem cells.

The Role of Therapeutic Drug Monitoring of Anti-Tumor Necrosis Factor Alpha Agents in Children and Adolescents with Inflammatory Bowel Disease.

BACKGROUND: Anti-tumor necrosis factor alpha (TNFα) therapy is effective in pediatric patients with inflammatory bowel disease (IBD) but associated with a risk of developing anti-drug antibodies (ADA) which lower the efficacy. Incorporating measurement of trough levels and ADA (therapeutic drug monitoring) may prevent the development of neutralizing ADA or could contribute to more optimal treatment strategies if ADA are already formed. The aim of this review was to investigate the role of therapeutic drug monitoring in children and adolescents with IBD exposed to anti-TNFα agents. METHODS: A literature search identified publications that measured anti-TNFα drug trough levels and/or ADA in children or adolescents with IBD. Studies were eligible when (1) article was written in English, (2) original data were available, (3) full text article or abstract was available, (4) measurement of antibodies against anti-TNFα drugs or trough level of anti-TNFα drugs were reported, and (5) levels were measured in pediatric patients with IBD. RESULTS: The search yielded 811 articles, of which 795 articles were excluded based on title or abstract. A total of 14 studies were included in the review. CONCLUSIONS: Therapeutic drug monitoring within the pediatric IBD population certainly has a potential benefit. As occurrence of immune reactions to anti-TNFα agents varies widely, incorporating measurement of IFX trough levels at week 8 or week 14 predicts therapy response and allows for dose adjustments to reach therapeutic drug concentrations. However, a clinically relevant cutoff level for ADA has not been defined yet, and the optimal intervention strategy still has to be determined.