Although CTLA-4 can be expressed at lower levels in other cell types and has been suggested as a negative regulator for naïve T cell activation, lineage-specific deletion of the Ctla4 gene in Foxp3+ Tregs results in development of systemic lymphoproliferation, fatal autoimmune disease, and potent tumor immunity (Wing et al., 2008). The gene discussed is FOXP3; the disease is autoimmune disease.