Located at Xp22.2, Toll-like receptor 7 and its functionally related gene TLR8 encode proteins that play critical roles in pathogen recognition and activation of innate immunity; they recognize endogenous RNA-containing autoantigens and when stimulated promote the expression of type I IFN, a pivotal cytokine in the pathogenesis of SLE. Here, TLR7 is linked to systemic lupus erythematosus.