To investigate the existence of circulating autoantibodies to erythropoietin (EPO) in sera from patients with systemic lupus erythematosus (SLE), and to correlate their presence with anemia and clinical activity.
Ninety-two consecutive patients with SLE, 80 patients with rheumatoid arthritis, and 42 normal individuals were studied. The patients with SLE were categorized into 3 groups according to hemoglobin (Hgb) level: group A (45 patients with Hgb > 12 gm/dl), group B (26 patients with Hgb 10.1-12 gm/dl), and group C (21 patients with Hgb < or = 10 gm/dl). In all patients with SLE, the disease activity was evaluated using the European Consensus Lupus Activity Measurement scale. Antibodies to EPO were detected using an enzyme-linked immunosorbent assay and purified recombinant human EPO as antigen. The specificity of the method was evaluated with homologous and cross-reactive inhibition assays.
Antibodies to EPO were found in 15.2% of the SLE patient sera. The distribution of these antibodies among the 3 groups of SLE patients was as follows: 8.8% (4 of 45) from group A, 15.4% (4 of 26) from group B, and 28.6% (6 of 21) from group C. The prevalence of antibodies to EPO in patients with severe anemia (group C) was statistically significantly higher compared with patients without anemia (chi(2) = 4.31, P < 0.05). Patients with antibodies to EPO had higher disease activity scores (P < 0.005) and lower levels of the C4 component of complement (P < 0.05) compared with patients without antibodies to EPO.
In this study, the presence of antibodies to EPO in the sera of SLE patients is demonstrated for the first time. The presence of these antibodies is associated with severe anemia and active disease.