The initial degree of host lymphopenia governs the expansion of regulatory T cells and, consequently, the development of adoptively transferred diabetes. (A) The prevalence of diabetes was determined in NOD SCID mice injected with 5 × 10⁴ (plain line) or 10 × 10⁶ (dotted line) CD4⁺ T cells from BDC2.5 NOD mice (n = 6). (B) Frequency of Foxp3-expressing cells among CD4⁺ T cells from the pancreatic LNs of NOD SCID mice injected with 5 × 10⁴ or 10 × 10⁶ BDC2.5 NOD CD4⁺ T cells. ***P < .001. (C) NOD SCID mice received 5 × 10⁴ (left) or 10 × 10⁶ (right) CD4⁺ or CD4⁺CD25⁻ T cells from BDC2.5 NOD mice (n = 4/group).