The association of CTLA-4 and HLA class II autoimmune risk genotype with regulatory T cell marker expression in 5-year-old children.

Regulatory T cells (Treg) are involved in the maintenance of peripheral tolerance by suppression of autoreactive lymphocytes that have avoided thymic depletion. The defective function of Treg cells has recently attracted attention in autoimmune diseases such as type 1 diabetes (T1D), rheumatoid arthritis and multiple sclerosis. Susceptibility to these diseases is associated with specific human leucocyte antigen (HLA) class II and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) gene polymorphisms. This study aimed to investigate the relationship between HLA class II and CTLA +49 A/G polymorphisms associated with susceptibility to T1D and the number and characteristics of Treg cells in children. Samples from 47 5-year-old children who participated in the All Babies in South-east Sweden (ABIS) follow-up study were grouped according to the presence of the T1D risk-associated HLA genotype (DQA1*0501-DQB1*0201, DQA1*0301-DQB1*0302) or neutral HLA genotypes. Lower percentages of CD4+ T cells (P = 0.03) and CD4+ CD25high cells (P = 0.06) expressing intracellular CTLA-4 were detected in samples from children with CTLA-4 +49GG compared to children with the +49AA genotype. Similarly, lower percentages of CD4+ (P = 0.002) and CD4+ CD25high (P = 0.002) cells expressing CTLA-4 were observed in children positive for HLA DQA1*0501-DQB1*0201 and DQA1*0301-DQB1*0302 (P = 0.04 for CD4+ and P = 0.02 for CD4+ CD25high) risk haplotypes when compared to children without these alleles. The percentage of CD25high cells among CD4+ cells was correlated inversely with CTLA-4 mRNA expression in PBMC (r = -0.56, P = 0.03). Decreased levels of CTLA-4 in CD4+ and CD4+ CD25high cells in individuals with CTLA-4 and HLA class II alleles associated with T1D may contribute to the initiation and/or progression of autoimmune response.

Diminished Th1-like response to autoantigens in children with a high risk of developing type 1 diabetes.

The exact role of T-helper (Th) cells that precede the clinical manifestation of type 1 diabetes remains unclear. The aim of this investigation was to study the Th1- and Th2-like profile in children and adults with high risk of developing the disease. Peripheral blood mononuclear cells were collected from high-risk children and adults and from healthy individuals matched for age and gender. Using the sensitive enzyme-linked immunospot (ELISPOT) technique to divide Th1- from Th2-like lymphocytes, secretion of interferon-gamma (IFN-gamma) and interleukin-4 was analysed from lymphocytes spontaneously and after in vitro stimulation with different antigens, based on present paradigms regarding the pathogenesis of type 1 diabetes. Compared to the response observed in healthy individuals, we found that individuals with a high risk of developing type 1 diabetes, especially children, responded with less IFN-gamma secretion to the three autoantigens glutamic acid decarboxylase 65 (GAD65), insulin and tyrosinphosphatase (IA-2). Thus, a diminished Th1-like response by in vitro autoantigen stimulation was observed in especially children with a high risk of developing type 1 diabetes. Reduced Th1/Th2 response was related to signs of beta cell exhaustion.

Cytokine profile in children during the first 3 months after the diagnosis of type 1 diabetes.

Type 1 diabetes is an autoimmune disease with an inflammatory process directed against the beta cells in pancreas. This investigation aimed at studying the immune response during the first 3 months after the diagnosis of type 1 diabetes, with focus on the balance of T-helper 1 (Th1)- and Th2-like cytokines, produced spontaneously and in response to relevant autoantigens. Peripheral blood mononuclear cells (PBMCs) were collected from type 1 diabetic children (10-17 years) at 5, 20, 35 and 90 days after diagnosis. Expression of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) mRNA were detected by real-time reverse transcriptase polymerase chain reaction and IFN-gamma, IL-10 and IL-13 by enzyme-linked immunosorbent assay in cell supernatant after stimulation with a glutamic acid decarboxylase 65 (GAD(65))-peptide [amino acid (a.a.) 247-279], insulin, the ABBOS-peptide (a.a. 152-169), phytohaemagglutinin and keyhole limpet haemocyanin. Spontaneous and antigen-induced expression and secretion of cytokines were low at the diagnosis of type 1 diabetes. During the first month, after diagnosis, the GAD(65)-peptide caused an increased ratio of IFN-gamma/IL-4 mRNA expression (P < 0.05) and increased secretion of IFN-gamma (P = 0.07). Expression of IFN-gamma mRNA did also increase from stimulation with insulin (P < 0.05), even though cytokine secretion remained low. Thus, duration after diagnosis as well as metabolic state should be carefully considered both in studies of the pathogenesis of type 1 diabetes and in immune intervention studies at onset.