CD4 and rheumatoid arthritis: These findings have an important impact on the understanding of the role of lactate in the context of immune‐mediated inflammatory disorders (IMIDs, i.e., rheumatoid arthritis [RA]) where lactate may act as an inflammatory signal leading to the inhibition of CD4+ T cell migratory capability and to their differentiation in a Th17 subset thus sustaining the chronic inflammatory process (Figure 2).