Cotransfer of Tgf-β1^-/- CD4⁺CD25⁺ T cells partially suppressed the activation and proliferation of T lymphocytes. (A) Spleens of Rag2^-/- recipients are shown. (B) Lymphocyte proliferation in spleen of Rag2^-/- recipient mice was determined by BrdU uptake. The numbers of BrdU-positive CD4⁺ and CD8⁺ cells in spleens of Rag2^-/- recipient mice are shown. (C) The numbers of CD69⁺ CD4⁺CD3⁺ and CD8⁺CD3⁺ cells in spleens of Rag2^-/- recipient mice are shown. (D) The numbers of CD25⁺ CD4⁺CD3⁺ and CD8⁺CD3⁺ cells in spleens of Rag2^-/- recipient mice are shown. Error bars (B-D) indicate SD.