Background: In recent years, we have detected autoantibodies in bone marrow (BM) hemopoietic cells in some patients with idiopathic cytopenia of undetermined significance (ICUS), termed immunorelated pancytopenia (IRP). However, we know little about the targets of these autoantibodies.
Methods: Twenty-six newly diagnosed IRP patients with IgG autoantibody on nucleated erythrocytes and 20 healthy donors as controls were enrolled in this study. The serum erythropoietin (EPO) level was examined by ELISA. Expression of EPO receptor (EPOR) and IgG autoantibody on the membrane of nucleated erythrocytes were detected by flow cytometry before and after autoantibody stripping.
Results: The serum EPO level of the untreated patients was 199.9 ± 106.4 mIU/mL, which was significantly higher than that of normal controls (13.2 ± 8.41 mIU/mL, p < 0.01). EPOR expression on nucleated erythrocytes in the patients was 1.38 ± 0.73%, lower than that of normal controls (2.33 ± 1.73%), but there was no significant difference; EPOR in these patients was inversely correlated with IgG autoantibody on erythrocytes (r = -0.479, p = 0.013). The regression equation was Y = 0.116-0.479X; EPOR expression on the membrane increased significiantly (5.63 ± 4.99%, p < 0.01) after stripping the autoantibodies. After immunosuppressive treatment, median hemoglobin increased from 72 g/L to 98 g/L, and median reticulocytes increased from 1.46% to 3.56%.
Conclusions: IgG autoantibodies might block or competitively inhibit EPOR on nucleated erythrocytes in some cases of ICUS.