CTLA4 and systemic lupus erythematosus: The genome-wide association studies (GWASs), which apply high-throughput genomic technologies, have identified many susceptible loci [7, 8], and several SLE-associated genes encoded at genetic risk loci, such as IL-2, PDCD1, CTLA4, and IL-21, are shown to be involved in the pathogenesis of SLE [9, 10].