Roles of Immunity and Endogenous Retroelements in the Pathogenesis of Rheumatoid Arthritis and Treatment Strategies.

Rheumatoid arthritis (RA) is a chronic, inflammatory, autoimmune disease that primarily affects the joints. RA usually results in synovial hyperplasia, expansion of "pannus" and destruction of cartilage. The etiology and pathogenesis of RA are not fully understood, but immunity has been shown to play an important role in the development of autoimmune diseases such as RA. In addition, endogenous retroelements, the remnants of ancient retroviruses in the human genome, are involved in cancer and/or immune disorders. As evidenced by increasing evidences that the aberrant expression of retroelements induces innate immunity, despite the fact that the expression of most retroelements has been epigenetically suppressed over a long period of evolution. With the continuous development of disease-modifying anti-rheumatic drugs (DMARDs), RA disease activity has been alleviated and improved. Unfortunately, some patients have a limited response to DMARDs, and the drugs also have the disadvantages of some side effects and high economic costs. This review summarizes the pathogenic mechanisms of RA and endogenous retroelements in autoimmunity, and concludes with a summary of treatments for RA, along with new therapeutic recommendations.