Figure 4. Anti-CTLA-4 acts to inhibit CD4⁺CD25⁺ T_R activity by interacting with CTLA-4 expressed by CD4⁺CD25⁺ cells.

(A) C.B-17.scid mice received WT CD4⁺CD45RB^high cells alone or in combination with either WT or B7-1/B7-2/CTLA-4 KO (triple KO (TKO)) CD4⁺CD25⁺ cells. In addition, some mice also received anti-CTLA-4 mAb. (B) In similar experiments, C.B-17.scid mice received B7-1/B7-2/CTLA-4 KO CD4⁺CD45RB^high cells alone or in combination with WT CD4⁺CD25⁺ cells. Again some mice also received anti-CTLA-4 mAb. Mice were sacrificed 6–8 wk after transfer and colons taken for histological analysis. Data show colitis scores for individual mice taken from two to three independent experiments.