TLR7 and rheumatoid arthritis: Despite the protective immune response of endosomal TLRs against invading pathogenic microorganisms, inappropriate engagement of TLR7/8 by host ssRNAs, such as microRNA or small interfering RNA released from dead/dying cells, propagates the pathogenesis of autoimmune diseases, namely psoriasis, systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA) [20,21].