IRF4 and synovitis: A lack of IRF4 resulted in a slight reduction in early synovitis, with once again a reduction in the proportion of synovial neutrophils, while a lack of CCL17 had no effect; however, in the absence of either GM-CSF [8], IRF4 or CCL17 there was no pain development at week 3 and significantly reduced histologic scores and osteophyte size at week 6 (Fig. 1a-c).