The p38 isoforms play a particularly important role in regulating the production of pro-inflammatory cytokines such as TNF-α, IL-1β, and IL-6, which are key mediators in autoimmune and inflammatory diseases such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), chronic obstructive pulmonary disease (COPD), and type 1 diabetes [99,100,101]. The gene discussed is TNF; the disease is rheumatoid arthritis.