Reduced frequency and functional potency of CD49- T regulatory cells in patients with newly diagnosed type 2 diabetes mellitus

This study set out to check the quantitative and qualitative properties of peripheral CD4(+)CD25(+)CD49d(-) T regulatory (CD49d(-) Treg) cells in type 2 diabetes mellitus (T2DM) patients. This work comprised 35 newly diagnosed patients and 35 healthy controls (HCs). The frequency of FoxP3 expressing CD49d(-) Treg cells was determined by flow cytometry. The gene expression of FoxP3 and CD49d was assessed by real-time PCR. Suppression assays with purified CD49d(-) Treg cells and CD4(+)CD25 T conventional (Tconv) cells were done by flow cytometry. The supernatants of Tconv/CD49d(-) Treg co-cultures were tested for IFN-gamma, IL-4, IL-17, and IL-10 using ELISA. The frequency of CD49d(-) Treg cells (by both CD4(+)CD25(+)CD49d(-) and CD4(+)CD25(++)CD49d(-) phenotypes) observed to be reduced in patients versus HCs. In the patients, decreased protein and gene expression of FoxP3 was seen in CD49d(-) Treg cells. Suppressive potency of CD49d(-) Treg cells to inhibit Tconv cells proliferation was diminished, and inversely related to fasting plasma glucose and hemoglobin A1c in the patients. Tconv cells from T2DM patients released higher amount of IL-17 and lower concentration of IL-10 versus HCs. In Tconv/CD49d(-) Tregs co-cultures, decreased IL-17 and increased IL-10 levels were seen in HCs, but not T2DM patients. CD49d(-) Treg cells from the patients have a fundamental defect and Treg cells fail to inhibit the aggressive inflammatory responses.