Biochemical analysis of ferritin subunits in sera from adult Still's disease patients.

To determine the origin of the increased serum ferritin that occurs in adult Still's disease (ASD), we analyzed subunits of the serum ferritin as follows. Gel filtration with Sepharose CL-6B demonstrated that the molecular weight of serum ferritin was about 490 kDa. Western blot analysis revealed only L-subunits (molecular weight 19 kDa) in patients with serum ferritin levels higher than 1,000 ng/ml. Patients with serum ferritin levels higher than 1,000 ng/ml, however, showed G-subunits (molecular weight 23 kDa) in addition to the L-subunits. When concanavalin A (Con-A) Sepharose 4B was used in an absorption test, the percentage absorption was extremely low in the patients with serum ferritin levels higher than 1,000 ng/ml. Isoferritin patterns of the patients determined by chromatofocusing revealed traces of acidic ferritin. The findings suggested that glycosylated ferritin does not account for the major portion of the increased serum ferritin.