We adoptively transferred into Rag2-KO mice CD45.1-marked EGFP+ Tregs (CD4+FoxP3EGFP+) isolated from either the spleens or colons of FoxP3EGFP SKG mice together with CD45.2-marked SKG CD4+ effector (CD4+CD25–) peripheral T cells and monitored development of arthritis after injection of mannan (Figure 4D and Supplemental Figure 8A). Here, CD4 is linked to arthritic joint disease.