IL4 and rheumatoid arthritis: Syngeneic fibroblasts have also shown promise as gene delivery ‘vehicles’ in a number of other experimental systems, such as delivery of IL-4 in collagen-induced rheumatoid arthritis (Bessis et al, 2002) and production of proteolipid protein to induce T-cell anergy in experimental autoimmune encephalomyelitis, the murine model of multiple sclerosis (Weiner et al, 2004).