These regulators are required for Treg‐induced immune suppression and homeostasis: deficiency of Foxp3 and CD152 impairs the immune activities of Tregs, causing fatal T cell‐induced autoimmune disease, systemic lymphoproliferation, and increased tumour immunity.1, 2, 3, 4 Herein, we found that prominent up‐regulation of Foxp3 and CD152 expression occurred in CD4+CD25+Tregs stimulated with IL‐38, and IL‐38 induced CD4+CD25+Tregs to augment the release of anti‐inflammatory IL‐10 and TGF‐β1. This evidence concerns the gene CTLA4 and autoimmune disease.