Thymic Atrophy and Immune Dysregulation in Infants with Complex Congenital Heart Disease.

Congenital heart disease (CHD) is the most common birth defect, and up to 50% of infants with CHD require cardiovascular surgery early in life. Current clinical practice often involves thymus resection during cardiac surgery, detrimentally affecting T-cell immunity. However, epidemiological data indicate that CHD patients face an elevated risk for infections and immune-mediated diseases, independent of thymectomy. Hence, we examined whether the cardiac defect impacts thymus function in individuals with CHD. We investigated thymocyte development in 58 infants categorized by CHD complexity. To assess the relationship between CHD complexity and thymic function, we analyzed T-cell development, thymic output, and biomarkers linked to cardiac defects, stress, or inflammation. Patients with highly complex CHD exhibit thymic atrophy, resulting in low frequencies of recent thymic emigrants in peripheral blood, even prior to thymectomy. Elevated plasma cortisol levels were detected in all CHD patients, while high NT-proBNP and IL-6 levels were associated with thymic atrophy. Our findings reveal an association between complex CHD and thymic atrophy, resulting in reduced thymic output. Consequently, thymus preservation during cardiovascular surgery could significantly enhance immune function and the long-term health of CHD patients.

Treating sarcoidosis-associated progressive multifocal leukoencephalopathy with infliximab.

Although most of the progressive multifocal leukoencephalopathy cases in sarcoidosis patients are explained by the treatment with immunosuppressive drugs, it is also reported in treatment-naive sarcoidosis patients, which implies a general predisposition of sarcoidosis patients for progressive multifocal leukoencephalopathy. Indeed, it was shown that active sarcoidosis patients have increased regulatory T cell frequencies which could lead to a subsequent systemic immunosuppression. However, if sarcoidosis with systemic changes of T cell subsets frequencies constitute a risk factor for the development of progressive multifocal leukoencephalopathy, which could then be counteracted by sarcoidosis treatment, is not known. In this cohort study, we included, characterized and followed-up six patients with bioptically confirmed definite progressive multifocal leukoencephalopathy and definite or probable sarcoidosis presenting between April 2013 and January 2019, four of them had no immunosuppressive therapy at the time of developing first progressive multifocal leukoencephalopathy symptoms. Analysis of immune cell subsets in these patients revealed significant imbalances of CD4+ T cell and regulatory T cell frequencies. Due to the progression of progressive multifocal leukoencephalopathy in four patients, we decided to treat sarcoidosis anticipating normalization of immune cell subset frequencies and thereby improving progressive multifocal leukoencephalopathy. Notably, by treatment with infliximab, an antibody directed against tumour necrosis factor-α, three patients continuously improved clinically, JC virus was no longer detectable in the cerebrospinal fluid and regulatory T cell frequencies decreased. One patient was initially misdiagnosed as neurosarcoidosis and died 9 weeks after treatment initiation due to aspiration pneumonia. Our study provides insight that sarcoidosis can lead to changes in T cell subset frequencies, which predisposes to progressive multifocal leukoencephalopathy. Although immunosuppressive drugs should be avoided in progressive multifocal leukoencephalopathy, paradoxically in patients with sarcoidosis treatment with the immunosuppressive infliximab might restore normal T cell distribution and thereby halt progressive multifocal leukoencephalopathy progression.

IL-17 production by CSF lymphocytes as a biomarker for cerebral vasculitis.

OBJECTIVE: To explore the possibility of using interleukin-17 (IL-17) production by CD4+ T cells in the CSF as a potential biomarker for cerebral vasculitis in stroke patients. METHODS: In this consecutive case study, we performed prospective analysis of CSF and blood in patients admitted to a university medical center with symptoms of stroke and suspected cerebral vasculitis. Flow cytometry was performed for intracellular detection of inflammatory cytokines in peripheral blood lymphocytes and expanded T cells from CSF. RESULTS: CSF CD4+ lymphocytes from patients with cerebral vasculitis showed significantly higher levels of the proinflammatory cytokine IL-17 compared to patients with stroke not due to vasculitis or with other, noninflammatory neurologic diseases. There was no difference in the production of interferon-γ in the CSF and no overall differences in the relative frequencies of peripheral immune cells. CONCLUSIONS: Intracellular IL-17 in CSF cells is potentially useful in discriminating cerebral vasculitis as a rare cause in patients presenting with ischemic stroke. CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that an increased proportion of IL-17-producing CD4+ cells in CSF of patients presenting with stroke symptoms is indicative of cerebral vasculitis (sensitivity 73%, 95% confidence interval [CI] 39-94%; specificity 100%, 95% CI 74%-100%).

Common variable immunodeficiency, impaired neurological development and reduced numbers of T regulatory cells in a 10-year-old boy with a STAT1 gain-of-function mutation.

Recently, gain-of-function (GOF) mutations in the gene encoding signal transducer and activator of transcription 1 (STAT1) have been associated with chronic mucocutaneous candidiasis (CMC). This case report describes a 10-year-old boy presenting with signs of common variable immunodeficiency (CVID), failure to thrive, impaired neurological development, and a history of recurrent mucocutaneous Candida infections. Sequencing of the STAT1 gene identified a heterozygous missense mutation in exon 7 encoding the STAT1 coiled-coil domain (c.514T>C, p.Phe172Leu). In addition to hypogammaglobulinemia with B-cell deficiency, and a low percentage of Th17 cells, immunological analysis of the patient revealed a marked depletion of forkhead-box P3(+)-expressing regulatory T cells (Tregs). In vitro stimulation of T cells from the patient with interferon-α (IFNα) and/or IFNÉ£ resulted in a significantly increased expression of STAT1-regulated target genes such as MIG1, IRF1, MX1, MCP1/CCL2, IFI-56K, and CXCL10 as compared to IFN-treated cells from a healthy control, while no IFNα/É£-mediated up-regulation of the FOXP3 gene was found. These data demonstrate that the STAT1 GOF mutation F172L, which results in impaired stability of the antiparallel STAT1 dimer conformation, is associated with inhibited Treg cell development and neurological symptoms.

The expression of CD39 on regulatory T cells is genetically driven and further upregulated at sites of inflammation.

Regulatory T cells (Tregs) use different mechanisms to exert their suppressive function, among them the conversion of ATP to adenosine initiated by the ectonucleotidase CD39. In humans, the expression of CD39 on Tregs shows a high interindividual variation, and is especially high at sites of inflammation, like the synovia of patients with arthritis. How CD39 expression is regulated, and the functional consequences of different levels of CD39 expression is not known. We show here that stimulation of CD39(-) Tregs results in a modest upregulation of CD39, which cannot explain the high levels observed in many donors. Moreover, CD39(+) Tregs are present in naïve compartments such as cord blood and thymus, and the individual frequency of CD39(+) Tregs remains stable over time, suggesting inherent regulation of CD39 expression. Indeed, we show that a single nucleotide polymorphism in the CD39 gene determines expression levels in Tregs. CD39(+) Tregs suppress T cell proliferation and inflammatory cytokine production more efficiently than CD39(-) Tregs. Accordingly, Tregs from donors with the GG (high CD39) genotype have a higher capacity to suppress IFN-γ and IL-17 production by effector cells than Tregs from AA (low CD39) donors. Our study demonstrates that the expression of CD39 in Tregs is primarily genetically driven, and this may determine interindividual differences in the control of inflammatory responses.

Effect of prenatal steroid treatment on the developing immune system.

UNLABELLED: Prenatal steroids have an undisputed positive effect of decreasing neonatal morbidity and mortality by improving fetal lung maturation. Some concerns have been raised on long-term consequences on the hypothalamic-pituitary-adrenal axis and cognition, but there are no studies addressing effects on the immune system. The thymus is an essential organ for the development and selection of T cells, and thymocytes are extremely sensitive to steroids. Using a mouse model for prenatal steroid administration, we show here that betamethasone treatment to the mother has a profound effect on the thymus of the offspring. We find the thymus volume reduced, affecting mostly the developing CD4+ CD8+ double-positive thymocytes and a compensatory accelerated transition of the earlier stages to replenish the depleted compartment. This effect lasts for at least 3 days, which correspond to a very relevant period for the selection of the T cell repertoire. Moreover, we show that low doses of betamethasone have similar effects on human thymocytes in vitro. Therefore, further studies are needed to analyze possible long-term consequences of this treatment on the immune system of the offspring. KEY MESSAGE: Betamethasone administered to the mother before birth reaches the fetal thymus. Prenatal betamethasone results in massive loss of developing thymocytes. The effects of betamethasone on thymus development are visible for several days. Human thymocytes are also sensitive to low doses of betamethasone. Altered thymocyte development around birth may have an effect on the immune system.

Phenotypical and functional characterization of T helper 17 cells in multiple sclerosis.

Multiple sclerosis is a T cell-mediated demyelinating disease of the central nervous system. Interleukin-17-producing T helper cells, named Th17 cells, represent a novel CD4+ T cell effector subset involved in the response against extracellular pathogens. In addition, Th17 cells are pathogenic in several animal models of autoimmune disease, including the animal model for multiple sclerosis, but their function in multiple sclerosis remains to be elucidated. In this study, we analysed the frequency and the phenotype of Th17 cells in the cerebrospinal fluid and peripheral blood of multiple sclerosis patients. We show that the frequency of Th17 cells is significantly higher in the cerebrospinal fluid of patients with relapsing-remitting multiple sclerosis during relapse, in comparison to relapsing-remitting patients in remission or to patients with other non-inflammatory neurological diseases. Similarly, in patients with clinically isolated syndrome during their first neurological episode, Th17 cells are more abundant than in clinically isolated syndrome patients with no acute symptoms. Patients with inflammatory neurological diseases other than multiple sclerosis also showed increased frequency of Th17 cells compared to patients with no inflammatory diseases. To assess a potential pathological impact of Th17 cells in disease, we generated T cell clones from the cerebrospinal fluid and peripheral blood of patients with multiple sclerosis. We found that Th17 clones expressed higher basal levels of the activation markers CD5, CD69, CD2 and human leukocyte antigen-DR as well as of the CD28-related family of co-stimulatory molecules, when compared to Th1 clones, and confirmed these findings with ex vivo human T cells. Molecules involved in T cell adhesion to endothelium, such as CD49d, CD6 and the melanoma cell adhesion molecule, were also more abundant on the Th17 than on the Th1 cells. Furthermore, functional assays showed that Th17 clones were more prone than Th1 clones to melanoma cell adhesion molecule-mediated adhesion to endothelial cells, and that Th17 cells had a higher proliferative capacity and were less susceptible to suppression than Th1 cells. Altogether our data suggest that Th17 cells display a high pathogenic potential and may constitute a relevant pathogenic subset in multiple sclerosis.

Phenotypical characterization of human Th17 cells unambiguously identified by surface IL-17A expression.

Th17 cells are involved in the defense against bacteria and fungi and play a prominent role in the pathogenesis of autoimmune diseases, but research on human Th17 cells is hindered due to the lack of a surface marker. In this study, we report that a subset of human and mouse CD4(+) T cells as well as human Th17 T cell clones express IL-17A on their surface upon stimulation. Correlation of surface IL-17A expression with intracellular IL-17A production and with RORgammat mRNA expression identified surface IL-17A as a specific marker for human and mouse Th17 cells. Phenotype characterization of ex vivo CD4(+) IL-17A(+) cells showed that the chemokines CCR6 and CCR4, costimulatory molecules, as well as CD2 and CD49d were more prominently expressed on these cells than in surface IL-17A(-) cells, supporting the concept of Th17 cells as a potent inflammatory effector subtype. In addition, we generated human Th1, Th1/17 (producing both IFN-gamma and IL-17A), and Th17 T cell clones based on single cell sorting of surface IL-17A(-), IL-17A(int), and IL-17A(high) CD4(+) T cells, respectively, and showed the plasticity of the double producing clones to the cytokine milieu. The identification of surface IL-17A as a marker for Th17 cells should facilitate research on this subset.