We recently demonstrated that synovial explants produce IL-6, monocyte chemo-attractant protein 1 (MCP-1) and macrophage inflammatory protein 1 beta (MIP-1b), and that this production was associated with colour Doppler ultrasound (CDUS) activity, magnetic resonance imaging (MRI) findings of synovitis, bone marrow oedema (BME), and erosions, using the RA MRI score (RAMRIS) and disease activity score 28 joints C-reactive protein (DAS-28) [16]. Here, CCL4 is linked to rheumatoid arthritis.