Introduction: T regulatory lymphocytes (Tregs) are defined as CD4+CD25high T lymphocytes and are thought to regulate immune tolerance. The Foxp3 protein level in Tregs is proportional to CD25 protein surface expression and regulatory function, but inversely proportional to IL-7R (CD127) level, the receptor for the growth and survival of T cells. We investigated possible differences in Tregs between newly diagnosed type 1 diabetes (DM1) patients and controls.
Materials and methods: Peripheral blood from 13 newly-diagnosed patients (9 M/4 F, ages 12.5±9.4 years) and 32 healthy controls (13 M/19 F, ages 25.3±11 years) was analyzed by triple colour flow cytometry for various phenotypic characteristics of Tregs. We used markers that had been linked to Treg function (FoxP3, CD28, CD45RO, CD127, CD152, TGFβ and its type II receptor TGFβRII), and proteins linked to apoptosis (CD95) and cell proliferation (CD27).
Results: Patients had lower percent of Tregs (as percent of total CD4+T cells) compared to controls: 1.259±0.264 vs 3.047±0.264% respectively, P<0.001. There was a higher frequency of expression of CD27 (which is linked to T cell proliferation) in patients compared to controls (mean±S.D., P value): 94.72±3.94 vs 79.53±30.40% respectively, P=0.012. Also, there was a decrease in the level of expression (expressed as Mean Fluorescence Intensity) of membrane TGFβ: 23.66±21.05 vs 53.82±62.48, P=0.029 and TGFβRII: 38.96±34.98 vs 123.72±214.15, P=0.043 in Tregs from patients compared to controls, respectively.
Conclusions: There are quantitative and qualitative differences in Tregs between patients with newly diagnosed DM1 and controls. This may account for the decreased immune tolerance in DM1.