TLR7 and systemic lupus erythematosus: Extracellular RNA, for example in immune complexes with the Ro protein (154), can also enter immune cells via receptor-mediated endocytosis followed by trafficking to the endosomal compartment where TLR3 will react to dsRNA and TLR7 and 8 with single-stranded RNA (as well as other ligands, see section TLRs in SLE).