Induction of GVHD in NOD-Scid mice by human PBMC and protection from GVHD by human regulatory T cells. (A-B) Different numbers of human PBMC as indicated were injected into newborn NOD-Scid mice. Untreated mice served as controls (n = 3). (A) Cumulative mean weight data; (B) survival of individual groups. Data from 1 representative experiment of 3 is shown. (C) Protection from GVHD by human Tregs. Newborn NOD-Scid mice were transferred with 10⁷ PBMC with or without graded numbers of Tregs. Each point represents the cumulative mean weight data of 4 mice per group. Survival of mice at day 37: untreated: 4/4; PBMC: 0/4; PBMC + Tregs 4:1: 4/4; PBMC + Tregs 10:1: 4/4; and PBMC + Tregs 20:1: 0/4. (D) Littermates 4 weeks after transfer of 10⁷ PBMCs with or without 2.5 × 10⁶ Tregs or untreated.