CXCL12 and rheumatoid arthritis: While we did observe a significant reduction in cell migration in response to CXCL12 and to the heterocomplex when monocytes were treated with IL-1β or IL-6 (Supplementary Figure 1), monocytes exposed to 1 nM PGE2 recapitulated the responses observed in monocytes from RA patients with active disease (Figures 3A,B and Supplementary Figure 1D).