OBJECTIVE: To examine the prevalence, clinical associations, and pathogenic role of autoantibodies to c-Mpl, the thrombopoietin (TPO) receptor, in patients with systemic lupus erythematosus (SLE). METHODS: Sera from 69 SLE patients, 84 patients with idiopathic thrombocytopenic purpura (ITP), and 60 healthy individuals were screened for anti-c-Mpl antibodies by enzyme-linked immunosorbent assay using recombinant c-Mpl as an antigen. Clinical findings, autoantibody profiles, and serum TPO levels were compared between SLE patients with and without anti-c-Mpl antibodies. A pathogenic role for the anti-c-Mpl antibody was evaluated by examining its inhibitory effect on TPO-dependent cell proliferation and megakaryocyte colony formation. RESULTS: Serum anti-c-Mpl antibody was detected in 8 SLE patients (11.6%) and 7 ITP patients (8.3%), but in none of the healthy controls. Anti-c-Mpl antibody was associated with thrombocytopenia (P = 0.0002) and a decrease in bone marrow megakaryocytes (P = 0.02) in SLE patients. Serum TPO levels in thrombocytopenic SLE patients with anti-c-Mpl antibodies were significantly elevated compared with levels in those without the antibodies (P = 0.007). IgG fractions purified from anti-c-Mpl antibody-positive sera bound to c-Mpl expressed on the cell surface and inhibited TPO-dependent cell proliferation and megakaryocyte colony formation. CONCLUSION: Autoantibody to c-Mpl is present in a subset of SLE patients with thrombocytopenia and megakaryocytic hypoplasia. It is likely that the impaired thrombopoiesis in these patients is mediated by the anti-c-Mpl antibody, which functionally blocks an interaction between TPO and c-Mpl.
OBJECTIVE: To examine the prevalence, clinical associations, and pathogenic role of autoantibodies to c-Mpl, the thrombopoietin (TPO) receptor, in patients with systemic lupus erythematosus (SLE). METHODS: Sera from 69 SLEpatients, 84 patients with idiopathic thrombocytopenic purpura (ITP), and 60 healthy individuals were screened for anti-c-Mpl antibodies by enzyme-linked immunosorbent assay using recombinant c-Mpl as an antigen. Clinical findings, autoantibody profiles, and serum TPO levels were compared between SLEpatients with and without anti-c-Mpl antibodies. A pathogenic role for the anti-c-Mpl antibody was evaluated by examining its inhibitory effect on TPO-dependent cell proliferation and megakaryocyte colony formation. RESULTS: Serum anti-c-Mpl antibody was detected in 8 SLEpatients (11.6%) and 7 ITP patients (8.3%), but in none of the healthy controls. Anti-c-Mpl antibody was associated with thrombocytopenia (P = 0.0002) and a decrease in bone marrow megakaryocytes (P = 0.02) in SLEpatients. Serum TPO levels in thrombocytopenic SLEpatients with anti-c-Mpl antibodies were significantly elevated compared with levels in those without the antibodies (P = 0.007). IgG fractions purified from anti-c-Mpl antibody-positive sera bound to c-Mpl expressed on the cell surface and inhibited TPO-dependent cell proliferation and megakaryocyte colony formation. CONCLUSION: Autoantibody to c-Mpl is present in a subset of SLEpatients with thrombocytopenia and megakaryocytic hypoplasia. It is likely that the impaired thrombopoiesis in these patients is mediated by the anti-c-Mpl antibody, which functionally blocks an interaction between TPO and c-Mpl.
Authors: Wei Zhang; Suying Dang; Jianhui Wang; Michael A Nardi; Hong Zan; Paolo Casali; Zongdong Li Journal: Autoimmunity Date: 2010-09-09 Impact factor: 2.815