Because FTY720 has a strong effect on CD4+ T-cell recirculation, and because collagen-induced arthritis is mediated by CII-specific CD4+ T cells [28], we investigated how FTY720 affected the development of the CD4+ CII-specific autoimmune T-cell response in the DR1 Tg mice (Fig. 4). Here, CD4 is linked to arthritic joint disease.