TNF and rheumatoid arthritis: An imbalance in the M1/M2 ratio at the site of disease results in an increase in the production of proinflammatory factors (IL-1β, iNOS, TNF-α, and IL-6) and matrix metalloproteinases (MMPs) by M1-type macrophages, which have been implicated in the pathogenesis of RA and can exacerbate joint damage [6, 7].