The existence of such interdependence may not be at all that surprising given the prior evidence for the links, for example, between TNF and IL-23 [3], TNF and GM-CSF [15], GM-CSF and IL-23 [17, 41], and the evidence of a GM-CSF/CCL17 axis in monocytes/macrophages [14] and in RA patients [55, 56]. The gene discussed is TNF; the disease is rheumatoid arthritis.