TNF and rheumatoid arthritis: These studies have shown that RA is a global disease distributed worldwide regardless of race, sex, ethnicity, nationality, age, etc. However, prevalence and incidence measurements vary according to population characteristics and change over time.[3] Although the mechanisms of RA have not been fully elucidated, studies have reported the involvement of cytokines such as tumor necrosis factor-α (TNF-α) and interleukin 6 in the pathophysiological processes of RA.[4]