CSF2 and Arthritis: We have previously reported that loss of Myd88 or GM‐CSF did not influence the development of arthritis in BPSM1 mice.3 Similarly, no difference in iBALT and NLH was noticed in BPSM1 m/+Myd88−/− and BPSM1 m/+GMCSF−/− animals (Supplementary figure 1b, c).