Studies on Iron and Immunity : Serum and Urinary Ferritin　Levels and Ferritin Contents of Leukocytes in Patients with Rheumatoid Arthritis

The serum and urinary ferritin levels and peripheral blood or synovial fluid leukocyte ferritin contents of 76 patients with rheumatoid arthritis (RA) were measured by the 2-site immunoradiometric assay method. Serum ferritin (s-fer.) levels of RA patients (mean±SD=33.9±26.3ng/ml, n=45) were within the normal range, although the s-fer. level correlated well with the amount of C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), γ-globulin level, RA test and disease activity. Urinary ferritin (u-fer.) levels of RA patients (8.7±12.7ng/ml, n=45) were not significantly different from controls (5.1±4.1ng/ml, n=23). However, when RA patients were divided into groups according to the therapy received at time of measurement, u-fer. level of RA patients under gold therapy (14.1±20.2ng/ml, n=15), but not those of patients under other treatments, were significantly higher than control level. The U/S ratio also tended to be higher. In addition, a remarkably high u-fer. level (over 300ng/ml) and U/S ratio (5.84) were found in are RA patient with gold nephropathy, indicating ferritin synthesis in kidney tissue. Ferritin contents of the supernatants of leukocytes were measured. Synovial fluid leukocytes (PMN : 29.7±9.5 fg/cell (n=16 ; MNC : 62.4±7.1 fg/cell (n=16)) tended to have higher ferritin contents than peripheral blood leukocytes (PMN : 5.3±2.6 fg/cell (n=16) ; MNC : 9.3±3.3 fg/cell (n=16)). There was no significant correlation between the ferritin contents of PMN or MNC of peripheral blood or synovial fluid and other parameters such as ferritin levels, ESR, CRP or RA test, except for a positive correlation between the ferritin contents of peripheral blood PMN and serum iron levels.