Yaa mice have a mutation characterized by translocation of a portion of the X chromosome (which contains the gene encoding Tlr7) onto the Y chromosome, and male BXSB/Yaa mice develop severe autoimmune disease consistent with SLE, with approximately 90% of mice developing fatal immune glomerulonephritis by 8 to 9 months of age [15]. This evidence concerns the gene TLR7 and systemic lupus erythematosus.