Erythrocyte complement receptor type 1 in non-SLE rheumatic diseases.

An investigation was conducted to measure the levels of erythrocyte complement receptor type 1 (CR1) in patients with various rheumatic diseases other than systemic lupus erythematosus, and to evaluate the clinical significance of this receptor in patients with ankylosing spondylitis (AS) and rheumatoid arthritis (RA). Erythrocyte CR1 was measured in 37 normal controls and 106 patients with various rheumatic diseases. The levels of erythrocyte CR1 decreased significantly in patients with AS, juvenile rheumatoid arthritis, Sjögren's syndrome, and RA, while there was no statistical difference in levels of erythrocyte CR1 between normal controls and patients with gouty arthritis. This suggests that erythrocyte CR1 deficiency may occur in immune-mediated rheumatic diseases such as crystal-induced arthritis. In this study, we noted that the levels of erythrocyte CR1 were not related to the disease activity and severity of AS. The levels of erythrocyte CR1 were also not correlated with the clinical and laboratory parameters of disease activity in RA patients. However, there was a negative association between the levels of erythrocyte CR1 and titer of rheumatoid factor in RA patients. Further study is needed to determine whether or not the level of erythrocyte CR1 is related to prognosis in patients with RA.