TNF and rheumatoid arthritis: Although several groups have demonstrated the different mechanisms of action for the preventive and curative efficacy of MSCs in RA, these groups have primarily focused on the regulation of immunocompetent cells, mainly autoreactive T and B lymphocytes.18, 19 More recently, accumulating evidence has shown that macrophages are responsible for the exacerbation of inflammatory responses and collateral damage in RA.20 Indeed, macrophages produce the core cytokines involved in RA pathogenesis, including TNF-α and IL-1β,21 which are targeted by current biologic medications.