The IL-12B rs17860508 (-6415 CTCTAA/GC) variant, associated with a risk for developing endometriosis and SLE [51,52], is located in a putative binding site for transcriptional factor specificity protein 1 (Sp-1) [92] and has been associated with alterations at the gene expression levels and mRNA stability, with the GC allele in IL-12B promoter exhibiting stronger activity upon binding of Sp1 and leading finally to higher cytokine production [93]. Here, SP1 is linked to endometriosis.