CTLA4 and systemic lupus erythematosus: One such strictly Treg cell-specific epigenetic element was found at the CTLA4 locus, which harbors a risk allele for multiple autoimmune disorders, including rheumatoid arthritis, type 1 diabetes (T1D), Graves' disease, and systemic lupus erythematosus (Scalapino and Daikh, 2008).