IRF5 and systemic lupus erythematosus: Polymorphisms in the IRF5 gene define haplotypes that can have a protective or exacerbating (risk) effect on lupus susceptibility, with the risk haplotype being characterized by the presence of Single Nucleotide Polymorphisms (SNPs) in the promoter region and 3′ untranslated region (UTR) which result in enhanced levels of IRF5 mRNA.