Defects in IL-2R Signaling Contribute to Diminished Maintenance of FOXP3 Expression in CD4+CD25+ Regulatory T-Cells of Type 1 Diabetic Subjects

Abstract

OBJECTIVEIn humans, multiple genes in the interleukin (IL)-2/IL-2 receptor (IL-2R) pathway are associated with type 1 diabetes. However, no link between IL-2 responsiveness and CD4+CD25+FOXP3+ regulatory T-cells (Tregs) has been demonstrated in type 1 diabetic subjects despite the role of these IL-2–dependent cells in controlling autoimmunity. Here, we address whether altered IL-2 responsiveness impacts persistence of FOXP3 expression in Tregs of type 1 diabetic subjects.RESEARCH DESIGN AND METHODSPersistence of Tregs was assessed by culturing sorted CD4+CD25hi natural Tregs with IL-2 and measuring FOXP3 expression over time by flow cytometry for control and type 1 diabetic populations. The effects of IL-2 on FOXP3 induction were assessed 48 h after activation of CD4+CD25− T-cells with anti-CD3 antibody. Cytokine receptor expression and signaling upon exposure to IL-2, IL-7, and IL-15 were determined by flow cytometry and Western blot analysis.RESULTSMaintenance of FOXP3 expression in CD4+CD25+ Tregs of type 1 diabetic subjects was diminished in the presence of IL-2, but not IL-7. Impaired responsiveness was not linked to altered expression of the IL-2R complex. Instead, IL-2R signaling was reduced in Tregs and total CD4+ T-cells of type 1 diabetic subjects. In some individuals, decreased signal transducer and activator of transcription 5 phosphorylation correlated with significantly higher expression of protein tyrosine phosphatase N2, a negative regulator of IL-2R signaling.CONCLUSIONSAberrant IL-2R signaling in CD4+ T-cells of type 1 diabetic subjects contributes to decreased persistence of FOXP3 expression that may impact establishment of tolerance. These findings suggest novel targets for treatment of type 1 diabetes within the IL-2R pathway and suggest that an altered IL-2R signaling signature may be a biomarker for type 1 diabetes.

Characteristics of rapid vs slow progression to type 1 diabetes in multiple islet autoantibody-positive children

“…It has been hypothesised that subsets of genes are acting to compromise pathways in type 1 diabetes that are related to IL-2 production and signalling [31][32][33]. Interestingly, 75% of the slow progressors in our study, in contrast to only 26% of the rapid progressors, were homozygous for the nonsusceptible IL2 allele.…”

“…It is also noteworthy that, in human type 1 diabetes, the IL2 gene was recently reported to be associated with the age of onset of diabetes [36]. Alleles of the CD25 gene predisposing to type 1 diabetes lower the expression of the high-affinity alpha-chain (CD25) of the IL-2 receptor on the surface of the T cells, which affects IL-2 signalling and may result in an impaired function of the T regulatory cells [31,33]. In addition to IL2 and CD25, several other loci associated with human type 1 diabetes encode molecules that play a role in the immune regulation of T cell-mediated adaptive immune responses, or of inflammatory signals provided by the innate immune system [30].…”

Regulatory T cells in vitiligo: Implications for pathogenesis and therapeutics

“…Several Tregs in patients with type 1 diabetes [101]. In addition, allogenic stem cell transplantation was found to lead to full recovery from primary biliary cirrhosis where peripheral blood lymphocytes were completely deficient in the -subunit of the IL-2R (CD25) [102].…”

Regulatory T cell therapy for type 1 diabetes: May the force be with you

“…Individuals carrying the rs12722495 susceptibility gene, which encodes an IL-2RA haplotype, exhibit reduced proliferative responses to IL-2 and decreased suppressive function of Tregs in vitro, which presumably indicates impaired Treg function in these patients [40,41]. Notably, in response to IL-2, this defect appears to be reversible: in a previously conducted clinical trial of exogenous IL-2, the impaired STAT5 phosphorylation was improved [39,42].…”

“…A previous report noted that Tregs from subjects with T1D may have impaired function due to an IL-2 signaling defect, with reduced phosphorylation of STAT5 (pSTAT5) [39]. This transcription factor is essential for Treg expansion and survival.…”