Insulin treatment in patients with type 1 diabetes induces upregulation of regulatory T-cell markers in peripheral blood mononuclear cells stimulated with insulin in vitro.
Patients with type 1 diabetes are treated with daily injections of human insulin, an autoantigen expressed in thymus. Natural CD4(+)CD25(high) regulatory T-cells are derived from thymus, and accordingly human insulin-specific regulatory T-cells should exist. We had a chance to study peripheral blood mononuclear cells (PBMCs) from children with type 1 diabetes both before and after starting insulin treatment, and thus we could analyze the effects of insulin treatment on regulatory T-cells in children with type 1 diabetes. PBMCs were stimulated for 72 h with bovine/human insulin. The mRNA expression of regulatory T-cell markers (transforming growth factor-beta, Foxp3, cytotoxic T-lymphocyte antigen-4 [CTLA-4], and inducible co-stimulator [ICOS]) or cytokines (gamma-interferon [IFN-gamma], interleukin [IL]-5, IL-4) was measured by quantitative RT-PCR. The secretion of IFN-gamma, IL-2, IL-4, IL-5, and IL-10 was also studied. The expression of Foxp3, CTLA-4, and ICOS mRNAs in PBMCs stimulated with bovine or human insulin was higher in patients on insulin treatment than in patients studied before starting insulin treatment. The insulin-induced Foxp3 protein expression in CD4(+)CD25(high) cells was detectable in flow cytometry. No differences were seen in cytokine activation between the patient groups. Insulin stimulation in vitro induced increased expression of regulatory T-cell markers, Foxp3, CTLA-4, and ICOS only in patients treated with insulin, suggesting that treatment with human insulin activates insulin-specific regulatory T-cells in children with newly diagnosed type 1 diabetes. This effect of the exogenous autoantigen could explain the difficulties to detect in vitro T-cell proliferation responses to insulin in newly diagnosed patients. Furthermore, autoantigen treatment-induced activation of regulatory T-cells may contribute to the clinical remission of the disease.
Tiittanen
Minna
M
National Public Health Institute, Department of Viral Diseases and Immunology, Laboratory for Immunology, Mannerheimintie 166, 00300 Helsinki, Finland. minna.tiittanen@ktl.fi
Huupponen
Johanna T
JT
Knip
Mikael
M
Vaarala
Outi
O
D000293:Adolescent; D015703:Antigens, CD / Q000235:genetics; D000943:Antigens, Differentiation / Q000235:genetics; D000945:Antigens, Differentiation, T-Lymphocyte / Q000235:genetics; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism; D060908:CTLA-4 Antigen; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000188:drug therapy* / Q000276:immunology; D005260:Female; D051858:Forkhead Transcription Factors / Q000235:genetics; D006442:Glycated Hemoglobin / Q000032:analysis; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use; D060889:Inducible T-Cell Co-Stimulator Protein; D007223:Infant; D007328:Insulin / Q000494:pharmacology / Q000627:therapeutic use*; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000276:immunology*; D008297:Male; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*
D015703:Antigens, CD; D000943:Antigens, Differentiation; D000945:Antigens, Differentiation, T-Lymphocyte; D015415:Biomarkers; D001786:Blood Glucose; D060908:CTLA-4 Antigen; D051858:Forkhead Transcription Factors; D006442:Glycated Hemoglobin; D007004:Hypoglycemic Agents; D060889:Inducible T-Cell Co-Stimulator Protein; D007328:Insulin; C556706:CTLA4 protein, human; C418974:FOXP3 protein, human; C556692:ICOS protein, human