Ferritin subunits in sera and synovial fluids from patients with rheumatoid arthritis

Objective, To determine the proportion of glycosylated ferritin [ferritin b ound to concanavalin A (Con-A)] and ferritin subunits in sera and synovial fluids (SF) from patients with rheumatoid arthritis (RA). Methods, Ferritin concentrations were measured by a sandwich ELISA using ra bbit IgG F(ab')(2) anti-human ferritin antibody as a coating antibody. Prop ortions of glycosylated ferritin were examined using Con-A Sepharose 4B. Fe rritin subunits were tested by Western blot analysis. Results. Ferritin concentrations in RA SF were significantly elevated compa red to those in osteoarthritis (OA) SF (p < 0.01) and those in RA sera (p < 0.01). Percentages of glycosylated ferritin in SF were low in both RA and OA (RA 11.9 +/- 10.7, n = 41; OA 6.9 +/- 11.0, n = 10). However percentages of glycosylated ferritin in RA sera (65.9 +/- 15.0, n = 20) were significa ntly higher than in RA SF (p < 0.01). Western blot analysis revealed both G subunit (23 kDa) and L subunit (19 kDa) in RA sera, although SF ferritin w as composed mostly of L subunit. Conclusion. Significant differences in ferritin molecule composition were o bserved between sera and SF from patients with RA, which suggests that in R A most SF ferritin is synthesized locally in the affected joint.