In Vivo Control of Diabetogenic T-Cells by Regulatory CD4⁺CD25⁺ T-Cells Expressing Foxp3

Abstract

To understand the ability of regulatory T-cells to control diabetes development in clinically relevant situations, we established a new model of accelerated diabetes in young DP-BB rats by transferring purified T-cells from DR-BB rats made acutely diabetic. Transfer of 3, 5, 10, or 23 million pure in vitro−activated T-cells accelerated diabetes onset in >90% of the recipients, with the degree of acceleration being dosage dependent. Cotransfer of unfractionated leukocytes from healthy donors prevented diabetes. Full protection was achieved when protective cells were transferred 3–4 days before diabetogenic cells, whereas transfer 2 days before conferred only partial protection. Protection resided in the CD4⁺ fraction, as purified CD4⁺ T-cells prevented the accelerated diabetes. When CD25⁺ cells were depleted from these cells before they were transferred, their ability to prevent diabetes was impaired. In contrast, two million CD4⁺CD25⁺ cells (expressing Foxp3) prevented the accelerated diabetes when transferred both before and simultaneously with the diabetogenic T-cells. In addition, 2 million CD4⁺CD25⁺ T-cells prevented spontaneous diabetes, even when given to rats age 42 days, whereas 20 million CD4⁺CD25⁻ cells (with low Foxp3 expression) were far less effective. We thus demonstrated that CD4⁺CD25⁺ cells exhibit powerful regulatory potential in rat diabetes.