Of special interest are variants in the Major Histocompatibility Genes (MHC), which are associated with the susceptibility of both SLE (HLA-DRB1 [12]) and LN (HLA-DQb1). Other genes involved in lymphocyte activation and inflammation have also been associated with SLE susceptibility, such as IKZF2 [13], STAT4 [14], IL-10 [15] and TNIP1 [2,15]. This evidence concerns the gene STAT4 and systemic lupus erythematosus.