Tuure Kinnunen

CTLA-4 is an inhibitory receptor on T cells that limits immune activation by competing with the co-stimulatory receptor CD28 for binding to CD80 and CD86 on antigen-presenting cells. Regulatory T cells (Tregs) employ CTLA-4–mediated transendocytosis as a key suppressive mechanism. Several CTLA4 polymorphisms are associated with autoimmune disease risk and may modulate CTLA-4 expression and function. Here, we analyzed samples from 155 genotyped subjects using flow cytometry and functional assays to determine how haplotypes formed by 3 CTLA4 single-nucleotide polymorphisms shape T-cell phenotype and function ex vivo. The autoimmune-protective CTLA4 rs5742909-rs231775-rs3087243 CAA haplotype was linked to increased intracellular CTLA-4 expression in both Tregs and conventional CD4+ T cells compared with CGG, CAG, and TAG haplotypes, implicating rs3087243 as the likely causal variant. The CAA haplotype was also associated with increased Treg frequencies. In Tregs from CAA/CAA subjects, elevated steady-state CTLA-4 expression promoted enhanced early CTLA-4 surface mobilization following anti-CD3/anti-CD28 stimulation. Moreover, naïve Tregs from CAA/CAA subjects more effectively suppressed naïve CD4+ T-cell proliferation in the presence of CD80/CD86-expressing dendritic cells. Collectively, these findings indicate that the rs3087243-A–linked CAA haplotype is associated with increased CTLA-4 expression and enhanced Treg function, providing a mechanistic explanation for its protective association with autoimmunity.

Objective: Patients with juvenile idiopathic arthritis (JIA) frequently exhibit antinuclear antibodies (ANAs), but the specific antigen target recognized by them and the presence of additional autoantibody specificities in patients with JIA remains elusive. Methods: Plasma samples from 110 untreated patients with active JIA, as well as from 14 children with unspecified arthritis and 151 age‐ and sex‐matched healthy children, were analyzed with multiple modern clinical‐grade autoantibody assays, including automated indirect immunofluorescence to screen for ANAs with HEp‐2 cells, and specific immune assays to detect reactivity to individual autoantigens. In addition, a HuProt proteome microarray was used to screen for novel autoantibody targets in plasma samples from five patients with ANA‐positive JIA and four ANA‐negative healthy controls. Results: Homogeneous nuclear ANA staining, indicating reactivity toward chromatin, was detected in most (61.8%) patients with JIA but rarely in healthy controls (2.6%; P < 0.0001). No antibody reactivity to specific nuclear antigens or other autoantigens associated with connective tissue diseases was detected. However, 20% of patients with JIA harbored antibodies against double‐stranded DNA (dsDNA)–nucleosome complexes (compared with 2.6% of controls, P < 0.0001). Finally, the proteome microarray revealed core histone H2A variant H2AFY, part of the nucleosome, to be the most widely recognized human protein by autoantibodies of patients with JIA. Conclusion: Autoantibody reactivity in JIA primarily targets chromatin, but the epitopes targeted are likely either posttranslationally modified or multimolecule epitopes, such as dsDNA–nucleosome complexes, rather than epitopes on individual native proteins or purified dsDNA.

Autologous hematopoietic cell transplantation (AHCT) is usually considered a single high-dose therapy intending to eradicate existing malignant cells from the patient and enabling both hematologic and immune recovery after the graft infusion. In addition to tumor biology and disease status, also the immunologic status of the patient and several factors affecting graft cellular content are crucial for posttransplant outcomes. There is evidence for an immunotherapeutic role of immune effector cells within infused grafts and of importance of immune recovery post-transplant. Here we present the pros and cons of this autograft-versus-tumor effect in myeloma and non-Hodgkin lymphoma, the two most common current indications for AHCT. In addition, we discuss ways to potentially improve current treatment results by enhancing the immunotherapeutic effect of AHCT.

Circulating follicular (cTfh) and peripheral (cTph) T helper cells have been demonstrated to be expanded in several autoimmune diseases, including type 1 diabetes (T1D). Here, we examined the frequencies and phenotypes of these cells at different stages of T1D development and addressed their phenotypic and clonal relationships by analyzing samples from 27 children with newly diagnosed T1D, 29 autoantibody‐positive (AAb⁺) children who later progressed to T1D and 57 healthy, age‐matched controls. Higher frequencies of cTph cells were detected in children with T1D and AAb⁺ children by flow cytometry, but no phenotypic alterations compared with cTph cells from healthy children were observed. Through a single‐cell multiomics approach, we demonstrate that cTph cells appear phenotypically more heterogeneous compared with cTfh cells and that they exhibit phenotypic and clonal sharing with both cTfh as well as CXCR5⁻PD‐1^lo memory T cells. Finally, the frequencies of cTph or cTfh cells did not differ in 17 children analyzed during seroconversion for T1D‐associated autoantibodies, the earliest detectable time point for autoimmunity. Collectively, our data demonstrate that cTph cells are a highly heterogeneous population partially sharing features with cTfh cells and that their frequency but not phenotype is altered at later stages of progression to clinical T1D.

CD8+ T cells are perceived to play a major role in the pathogenesis of type 1 diabetes (T1D). In this study, we characterized the function and phenotype of circulating CD8+ memory T cells in samples from individuals at different stages of T1D progression using flow cytometry and single-cell multiomics. We observed two distinct CD8+ T-cell signatures during progression of T1D within the highly differentiated CD27−CD8+ memory T-cell subset. A proinflammatory signature, with an increased frequency of IFN-γ+TNF-α+ CD27−CD8+ memory T cells, was observed in children with newly diagnosed T1D (stage 3) and correlated with the level of dysglycemia at diagnosis. In contrast, a coinhibitory signature, with an increased frequency of KLRG1+TIGIT+ CD27−CD8+ memory T cells, was observed in islet autoantibody-positive children who later progressed to T1D (stage 1). No alterations within CD27−CD8+ memory T cells were observed in adults with established T1D or in children during the initial seroconversion to islet autoantibody positivity. Single-cell multiomics analyses suggested that CD27−CD8+ T cells expressing the IFNG+TNF+ proinflammatory signature may be distinct from those expressing the KLRG1+TIGIT+ coinhibitory signature at the single-cell level. Collectively, our findings suggest that distinct blood CD8+ T-cell signatures could be employed as potential biomarkers of T1D progression. Article Highlights:

IL-21 is a multifunctional cytokine linked with the pathophysiology of several autoimmune diseases, including type 1 diabetes. In this study, our aim was to examine plasma IL-21 levels in individuals at different stages of type 1 diabetes progression. We measured plasma IL-21 levels, as well as levels of other key pro-inflammatory cytokines (IL-17A, TNF-α and IL-6), from 37 adults with established type 1 diabetes and 46 healthy age-matched adult controls, as well as from 53 children with newly diagnosed type 1 diabetes, 48 at-risk children positive for type 1 diabetes-associated autoantibodies and 123 healthy age-matched pediatric controls using the ultrasensitive Quanterix SiMoA technology. Adults with established type 1 diabetes had higher plasma IL-21 levels compared to healthy controls. However, the plasma IL-21 levels showed no statistically significant correlation with clinical variables, such as BMI, C-peptide, HbA1c, or hsCRP levels, evaluated in parallel. In children, plasma IL-21 levels were almost ten times higher than in adults. However, no significant differences in plasma IL-21 levels were detected between healthy children, autoantibody-positive at-risk children, and children with newly diagnosed type 1 diabetes. In conclusion, plasma IL-21 levels in adults with established type 1 diabetes were increased, which may be associated with autoimmunity. The physiologically high plasma IL-21 levels in children may, however, reduce the potential of IL-21 as a biomarker for autoimmunity in pediatric subjects.

Forest floor, sod, and gardening facilities in daycare environment modulate skin and gut microbiota and immunoregulation.

Aims/hypothesis: Mucosal-associated invariant T (MAIT) cells are innate-like T cells that recognise derivatives of bacterial riboflavin metabolites presented by MHC-Ib-related protein 1 (MR1) molecules and are important effector cells for mucosal immunity. Their development can be influenced by the intestinal microbiome. Since the development of type 1 diabetes has been associated with changes in the gut microbiome, this can be hypothesised to lead to alterations in circulating MAIT cells. Accordingly, peripheral blood MAIT cell alterations have been reported previously in patients with type 1 diabetes. However, a comprehensive analysis of the frequency and phenotype of circulating MAIT cells at different stages of type 1 diabetes progression is currently lacking. Methods: We analysed the frequency, phenotype and functionality of peripheral blood MAIT cells, as well as γδ T cells, invariant natural killer T (iNKT) cells and natural killer (NK) cells with flow cytometry in a cross-sectional paediatric cohort (aged 2–15) consisting of 51 children with newly diagnosed type 1 diabetes, 27 autoantibody-positive (AAb⁺) at-risk children, and 113 healthy control children of similar age and HLA class II background. The frequency of MAIT cells was also assessed in a separate cross-sectional adult cohort (aged 19–39) of 33 adults with established type 1 diabetes and 37 healthy individuals of similar age. Results: Children with newly diagnosed type 1 diabetes displayed a proportional increase of CD8⁻CD27⁻ MAIT cells compared with healthy control children (median 4.6% vs 3.1% of MAIT cells, respectively, p = 0.004), which was associated with reduced expression of C-C chemokine receptor (CCR)5 (median 90.0% vs 94.3% of MAIT cells, p = 0.02) and β7 integrin (median 73.5% vs 81.7% of MAIT cells, p = 0.004), as well as decreased production of IFN-γ (median 57.1% vs 69.3% of MAIT cells, p = 0.04) by the MAIT cells. The frequency of MAIT cells was also decreased in AAb⁺ children who later progressed to type 1 diabetes compared with healthy control children (median 0.44% vs 0.96% of CD3⁺ T cells, p = 0.04), as well as in adult patients with a short duration of type 1 diabetes (less than 6 years after diagnosis) compared with control individuals (median 0.87% vs 2.19% of CD3⁺ T cells, p = 0.007). No alterations in γδ T cell, iNKT cell or NK cell frequencies were observed in children with type 1 diabetes or in AAb⁺ children, with the exception of an increased frequency of IL-17A⁺ γδ T cells in children with newly diagnosed diabetes compared with healthy control children (median 1.58% vs 1.09% of γδ T cells, p = 0.002). Conclusions/interpretation: Changes in the frequency and phenotype of circulating MAIT cells were detectable before, at the onset and after diagnosis of type 1 diabetes in cross-sectional cohorts. Our results suggest a possible temporal association between peripheral blood MAIT cell alterations and the clinical onset of type 1 diabetes.