Fig. 1.

Regulatory capacities of thymic CD4⁺CD25⁺ T cells. Diabetes was monitored in NOD–SCID recipients injected with diabetogenic cells alone (spleen cells from diabetic NOD mice, 5 × 10⁶, Diab) or with 1 × 10⁶ CD4⁺CD25⁺ thymocytes (A) or CD4⁺CD25⁺ splenocytes (B) isolated from 6-week-old NOD mice. A significant protection was observed (P < 0.0001) with both regulatory populations. Administration of anti-TGF-β antibody abrogated diabetes protection afforded only by CD4⁺CD25⁺ T cells from the spleen but not from the thymus (P < 0.016). (C) Suppression of CD4⁺CD25⁻ T cell proliferation by CD4⁺CD25⁺ thymocytes (n = 10). Antibodies to IL-10 receptor (50 μg/ml) or TGF-β (10 or 50 μg/ml) were added in the culture. Data were expressed as the percent inhibition.