In consideration of our previous work showing a progressively impaired Treg-mediated control over CD4+ Tcon activation in NZB/W F1 mice (11), it appears plausible that even in young, clinically healthy lupus-prone mice Treg control autoantigen-specific CD4+ T cells to a lesser degree than in a non-lupus-prone mouse strain, which facilitates their escape and clonal expansion. This evidence concerns the gene CD4 and systemic lupus erythematosus.