Ferritin subunits in sera and synovial fluids from patients with rheumatoid arthritis.
OBJECTIVE
To determine the proportion of glycosylated ferritin [ferritin bound 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 rabbit IgG F(ab')2 anti-human ferritin antibody as a coating antibody. Proportions of glycosylated ferritin were examined using Con-A Sepharose 4B. Ferritin subunits were tested by Western blot analysis.


RESULTS
Ferritin concentrations in RA SF were significantly elevated compared 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 significantly 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 was composed mostly of L subunit.


CONCLUSIONS
Significant differences in ferritin molecule composition were observed between sera and SF from patients with RA, which suggests that in RA most SF ferritin is synthesized locally in the affected joint.
Ota
T
T
Central Clinical Laboratory, University of Occupational and Environmental Health, Kitakyushu, Japan.
Katsuki
I
I
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000378:metabolism*; D015153:Blotting, Western; D003208:Concanavalin A / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005293:Ferritins / Q000097:blood* / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D011485:Protein Binding; D012217:Rheumatoid Factor / Q000276:immunology; D013582:Synovial Fluid / Q000737:chemistry* / Q000276:immunology
D003208:Concanavalin A; D005293:Ferritins; D012217:Rheumatoid Factor