First, GM-CSF is an essential growth factor for in vitro and in vivo DC development.22 Second, GM-CSF is found at high concentrations at sites of inflammation in several diseases including asthma,23 multiple sclerosis24 and RA.25 Therapeutic neutralising antibodies targeting GM-CSF have shown promise in phase II clinical trials in RA.26 This evidence concerns the gene CSF2 and rheumatoid arthritis.