CSF1 and rheumatoid arthritis: M-CSF (and its alternative ligand, IL-34) has been shown to mediate monocyte-macrophage maturation via the M-CSF receptor in other disease contexts (Lin et al., 2019; Aikawa et al., 2010; Preisser et al., 2014), and monoclonal antibody-mediated M-CSF receptor inhibition ameliorated cytokine production in human RA synovial explants and mitigated disease severity in murine collagen-induced arthritis (Garcia et al., 2016).