Two types of autoantibody-mediated thrombocytopenia in patients with systemic lupus erythematosus.
OBJECTIVE
To determine whether autoantibodies to two platelet-specific antigens, glycoprotein IIb/IIIa (GPIIb/IIIa) and thrombopoietin receptor (TPOR), contribute to thrombocytopenia in patients with systemic lupus erythematosus (SLE).


METHODS
Circulating B cells producing anti-GPIIb/IIIa antibodies and serum anti-TPOR antibodies were measured in 32 SLE patients with thrombocytopenia, 30 SLE patients without thrombocytopenia, 92 patients with idiopathic thrombocytopenia and 60 healthy controls. The megakaryocyte density in bone-marrow smears from all the patients with thrombocytopenia was evaluated.


RESULTS
Anti-GPIIb/IIIa and anti-TPOR antibody responses were more frequent in SLE patients with thrombocytopenia than in those without thrombocytopenia (88 vs 17%, P<0.0001; and 22% vs 0%, P=0.01, respectively). The frequencies of these platelet-related antibodies were comparable between SLE patients with thrombocytopenia and patients with idiopathic thrombocytopenia. Twenty-nine (91%) SLE patients with thrombocytopenia had either anti-GPIIb/IIIa or anti-TPOR antibody, and six had both. In SLE patients with thrombocytopenia, the anti-TPOR-positive patients had significantly higher frequencies of megakaryocytic hypoplasia and poorer therapeutic responses to corticosteroids and intravenous immunoglobulin than did the anti-TPOR-negative patients, most of whom had the anti-GPIIb/IIIa antibody alone.


CONCLUSIONS
Anti-GPIIb/IIIa and anti-TPOR antibodies are major factors contributing to SLE-associated thrombocytopenia, but the clinical presentations associated with these autoantibodies are different.
Kuwana
M
M
Division of Rheumatology, Department of Internal Medicine, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan. kuwanam@sc.itc.keio.ac.jp
Kaburaki
J
J
Okazaki
Y
Y
Miyazaki
H
H
Ikeda
Y
Y
D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D001402:B-Lymphocytes / Q000276:immunology; D005260:Female; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D016756:Immunoglobulins, Intravenous / Q000627:therapeutic use; D008180:Lupus Erythematosus, Systemic / Q000150:complications* / Q000276:immunology / Q000628:therapy; D008297:Male; D008533:Megakaryocytes / Q000473:pathology; D008875:Middle Aged; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000276:immunology; D011518:Proto-Oncogene Proteins / Q000276:immunology; D018121:Receptors, Cytokine / Q000276:immunology; D053628:Receptors, Thrombopoietin; D013921:Thrombocytopenia / Q000209:etiology* / Q000276:immunology / Q000473:pathology; D017211:Treatment Failure
D001323:Autoantibodies; D005938:Glucocorticoids; D016756:Immunoglobulins, Intravenous; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D011518:Proto-Oncogene Proteins; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; C082218:MPL protein, human