Prevention of experimental diabetes in Ins-HA mice by CD25⁺ cells from LvHA-injected TCR-HA mice. (A) Percentages of 6.5⁺ cells within CD4⁺CD25^– (open symbols) and CD4⁺CD25⁺ (closed symbols) splenocytes determined 1 to 2 months after injection of the GFP-expressing (LvGFP) or of the HA-expressing (LvHA) lentiviral vector. (B) Percentages of diabetic Ins-HA mice upon cotransfer of 5 × 10⁵ purified CD25⁺ peripheral T cells from TCR-HA transgenic mice injected in the thymus 10 days earlier with GFP-expressing (CD25⁺ LvGFP) or HA-expressing (CD25⁺ LvHA) lentiviral vectors. One-hundred percent of the mice became diabetic at day 10 without cotransfer of CD4⁺CD25⁺ cells (CTRL). Data were obtained with 5 or 6 mice per group in 2 separate experiments. (C) (Top panel) Overlay histograms of CFSE labeling of Thy1.1⁺ cells 4 days after transfer of CD25^– Thy1.1⁺ cells alone (solid line) or cotransfer of CD25^– Thy1.1⁺ cells and CD25⁺ Thy1.2⁺ cells (gray histogram) in pancreatic lymph nodes of Ins-HA mice. (Bottom panel) Statistic representation of the percentages of cells falling within each population of undivided CFSE⁺ (Undiv), intermediately divided (Int), or highly divided (High) cells defined as shown on the right panel. Results are from 3 mice per group in a single experiment. Not depicted are similar results obtained in 2 other experiments.