In knees of rabbits that had been presensitized with methylated bovine serum albumin and unilateral arthritis was induced by means of intra-articular injection of the same antigen, imaging at 1.5 T and 24 h after the contrast agent administration could evidence the ultrasmall superparamagnetic iron oxide (USPIO) uptake by phagocytic-active macrophages in the synovium of all the arthritic knees [71]. The gene discussed is ALB; the disease is Arthritis.