FVB/Fas−/− lupus-like mice had lymphadenopathy, splenomegaly, high proportion of CD4−CD8− T cells, IFNγ-producing T cells, and low proportion of Treg cells, and addition of IL-2 (25 ng/g bodyweight every 5 days, five times) restored the number of Treg cells and upregulated IFNγ expression (164). This evidence concerns the gene IL2 and systemic lupus erythematosus.