Reactivated CD4+Tm cells of T1D patients and siblings display an exaggerated effector phenotype with heightened sensitivity to activation-induced cell death

A study of 51 subtypes of peripheral blood immune cells in newly diagnosed young type 1 diabetes patients

Type 1 diabetes (T1D) results from autoimmune destruction of insulin-producing beta cells in pancreatic islets. Various immune cell populations are involved in disease development and natural course. However, to our knowledge, so far there are no comprehensive comparative investigations of all main immune cell populations and their most important subsets at the onset of disease. Therefore, in the current study, we analyzed 51 peripheral blood immune cell populations in 22 young T1D patients and in 25 age-matched controls using a comprehensive polychromatic flow cytometry panel developed for whole blood by the COST Action no. BM0907 ENTIRE (European Network for Translational Immunology Research and Education: From Immunomonitoring to Personalized Immunotherapy) consortium. We found that in T1D patients, frequencies and absolute counts of natural killer (NK) cells, dendritic cells (DC) and T cells, as well as their respective subsets, were significantly altered compared to controls. Further, we observed that changes in several cell populations (e.g. CD14⁺ CD16⁺ non-classical monocytes, plasmablasts) were dependent on the age of the patient. In addition to age-related changes, we also found that alterations in immune cell patterns were associated with parameters such as the presence of ketoacidosis and C-peptide serum levels. Our study provides a foundation for future studies investigating different cell lineages and their role in T1D and illustrates the value of polychromatic flow cytometry for evaluating all main peripheral immune cells and their subsets in whole blood samples.

CD4+ T-Cells With High Common γ Chain Expression and Disturbed Cytokine Production Are Enriched in Children With Type-1 Diabetes

The common gamma chain (γ_c) contributes to the formation of different cytokine receptors [e.g., IL-2 receptor (IL-2R), IL-7R, and IL-15R], which are important for generation of self-reactive T-cells in autoimmune diseases, like in type 1 diabetes (T1D). Whereas, the roles of membrane and soluble IL-2Rα and IL-7Rα variants in T1D disease pathogenesis are well-described, effects of γ_c expression and availability for dependent receptors remain elusive. We investigated expression of the γ_c and dependent receptors on T-cells and soluble γ_c concentrations in serum from patients with T1D (n = 34) and healthy controls (n = 27). Effector T-cell cytokines as well as IL-2, IL-7, and IL-15 induced STAT5 phosphorylation were analyzed to determine functional implications of differential γ_c expression of CD4⁺ T-cell subsets classified by t-distributed Stochastic Neighbor Embedding (t-SNE) analyses. We found increased γ_c and IL-7Rα expression of CD4⁺ T-cells from T1D patients as compared to controls. t-SNE analyses assigned differential expression to subsets of memory T-cells co-expressing γ_c and IL-7Rα. Whereas, γ_c expression was positively correlated with IL-2Rα in memory T-cells from healthy controls, no dependency was found for patients with T1D. Similarly, the effector T-cell cytokine, IL-21, correlated inversely with γ_c expression in healthy controls, but not in T1D patients. Finally, T1D patients with high γ_c expression had increased proportions of IL-2 sensitive pSTAT5⁺ effector T-cells. These results indicated aberrantly high γ_c expression of T-cells from T1D patients with implications on dependent cytokine receptor signaling and effector T-cell cytokine production.

Interleukin-7 receptor α-chain haplotypes differentially affect soluble IL-7 receptor and IL-7 serum concentrations in children with type 1 diabetes

BACKGROUND

Interleukin-7 receptor α-chain (IL7RA) haplotypes are associated with susceptibility for development of autoimmune diseases, including type 1 diabetes (T1D). A protective IL7RA haplotype which causes lower soluble IL-7R (sIL-7R) serum levels is hypothesized to restrict IL-7-availability for self-reactive T cells. Functional mechanisms affected by a risk-associated IL7RA haplotype are unknown.

METHODS

We investigated the influence of IL7RA haplotypes (tagged by rs6897932T for the protective or by rs1494555G for the risk haplotype) on sIL-7R and IL-7 serum concentrations as well as disease manifestation of children with T1D (n = 259). Possible effects of differential IL-7 serum concentrations on IL-7-mediated in vitro T cell functions (i.e. IL-7R regulation and cytokine expression) were measured in a second study group of children with T1D (n = 42).

RESULTS

We detected lower sIL-7R serum concentrations in children with T1D carrying protective or risk haplotypes as compared to reference haplotypes. sIL-7R levels were lowest in T1D children with the protective haplotype and lower IL-7 serum levels were exclusively detected in this study group. We found no evidence for dependency between IL-7 and sIL-7R serum concentrations and no association with T1D manifestation. Neither IL-7 nor sIL-7R serum levels were associated with mIL-7R regulation or IL-7-promoted T cell cytokine expression.

CONCLUSIONS

Children with T1D carrying autoimmunity risk- or protection-associated IL7RA haplotypes had both lower sIL-7R serum concentrations as compared to the reference haplotype, but only T1D children with the protective haplotype had lower IL-7 serum levels. Our results suggest additional functional mechanisms of autoimmunity-associated IL7RA variants independent from sIL-7R mediated regulation of IL-7 availability for T cells.

Dominant TNFα and impaired IL-2 cytokine profiles of CD4+ T cells from children with type-1 diabetes

Aberrantly activated CD4⁺ T memory cells play a central role in the development of type-1-diabetes. Interleukin-7 promotes generation of autoimmune memory T cells and increased Interleukin-7 availability is associated with type-1-diabetes susceptibility. T-cell-mediated immune pathology at onset of type-1-diabetes is well defined, but characteristics of long-term symptomatic disease stages remain largely elusive. In the present study, memory CD4⁺ T-cell activation and cytokine expression as well as sensitivity to Interleukin-7 in vitro were compared between patients with type-1-diabetes at clinical onset (n=25), long-term symptomatic disease (median duration 4.5 years, n=19) and matched healthy controls (n=21). T-cell responses of type-1-diabetes patients were characterized by higher frequencies of cytokine and activation marker expressing CD4⁺ memory T cells as compared to healthy controls. Notably, correction for individual cytokine expression levels revealed qualitative differences of cytokine profiles characterized by significantly increased TNFα and decreased IL-2-expressing T-cell proportions in long-term type-1-diabetes patients. IL-7-mediated T-cell co-stimulation induced quantitative and qualitative cytokine expression differences highly similar to type-1-diabetes-specific profiles. In addition, CD4⁺ memory T cells from children with long-term type-1-diabetes were more sensitive to in vitro IL-7 co-stimulation. Global transcriptome analysis revealed IL-7 induced expression differences of CD4⁺ T cells, including increased IL-2R expression and effects on subsequent T-cell receptor activation. We conclude that long-term symptomatic type-1-diabetes patients differed in memory T-cell cytokine profiles and Interleukin-7 co-stimulation. Regulation of IL-2 expression and sensitivity are affected with possible consequences for disease course and severity at long-term type-1-diabetes stages.

Tolerogenic Dendritic Cells from Poorly Compensated Type 1 Diabetes Patients Have Decreased Ability To Induce Stable Antigen-Specific T Cell Hyporesponsiveness and Generation of Suppressive Regulatory T Cells

Tolerogenic dendritic cells (tolDCs) may offer an interesting intervention strategy to re-establish Ag-specific tolerance in autoimmune diseases, including type 1 diabetes (T1D). T1D results from selective destruction of insulin-producing β cells leading to hyperglycemia that, in turn, specifically affects a patient's immune system. In this study, we prepared monocyte-derived tolDCs modulated by dexamethasone and vitamin D₂ from 31 T1D patients with optimal glycemic control and 60 T1D patients with suboptimal glycemic control and assessed their tolerogenic properties in correlation with metabolic state of patients. tolDCs differentiated from both groups of patients acquired a regulatory phenotype and an anti-inflammatory profile. Interestingly, tolDCs from well-controlled patients expressed higher levels of inhibitory molecules IL-T3 and PD-L1. Additionally, glutamic acid decarboxylase (GAD)65-loaded tolDCs from well-controlled patients decreased significantly primary Th1/Th17 responses, induced stable GAD65-specific T cell hyporesponsiveness, and suppressed markedly control DC-induced GAD65-specific T cell activation compared with poorly controlled patients. The ability of tolDCs from poorly controlled patients to induce durable GAD65-specific T cell hyporesponsiveness was reversed once the control of glycemia improved. In both groups of patients, tolDCs were able to induce regulatory T cells from autologous naive CD4⁺ T cells. However, regulatory T cells from well-controlled patients had better suppressive abilities. The functionality of tolDCs was confirmed in the adoptive transfer model of NOD-SCID mice where tolDCs delayed diabetes onset. These results suggest that metabolic control of T1D affects the functional characteristics of tolDCs and subsequent effector T cell responses. Metabolic control may be relevant for refining inclusion criteria of clinical trials in the settings of T1D.

Receptor for Advanced Glycation End Products (RAGE) in Type 1 Diabetes Pathogenesis

The receptor for advanced glycation end products (RAGE) is a novel protein increasingly studied in the pathogenesis of type 1 diabetes (T1D). RAGE is expressed by several immune cell types, including T cells, antigen-presenting cells, endothelial cells, and the endocrine cells of the pancreatic islets. RAGE binds various ligands including advanced glycation end products (AGEs), high-mobility group box protein 1 (HMGB1), S100 proteins, β-amyloid, β-sheet fibrils, and lipopolysaccharide. AGEs are a particularly interesting ligand because their exogenous introduction into the body can be accelerated by the consumption of AGE-rich processed foods. This review will detail RAGE isoforms and its ligands and discuss how RAGE binding on the aforementioned cells could be linked to T1D pathogenesis.

Obstacles and opportunities for targeting the effector T cell response in type 1 diabetes

Autoreactive lymphocytes display a programmed set of characteristic effector functions and phenotypic markers that, in combination with antigen-specific profiling, provide a detailed picture of the adaptive immune response in Type 1 diabetes (T1D). The CD4+ T cell effector compartment (referred to as "Teff" in this article) has been extensively analyzed, particularly because the HLA genes most strongly associated with T1D are MHC class II alleles that form restriction elements for CD4+ T cell recognition. This "guilt by association" can now be revisited in terms of specific immune mechanisms and specific forms of T cell recognition that are displayed by Teff found in subjects with T1D. In this review, we describe properties of Teff that correlate with T1D, and discuss several characteristics that advance our understanding of disease persistence and progression. Focusing on functional disease-associated immunological pathways within these Teff suggests a rationale for next-generation clinical trials with targeted interventions. Indeed, immune modulation therapies in T1D that do not address these properties of Teff are unlikely to achieve durable clinical response.