Immunoglobulins targeting both GPIIb/IIIa and GPIb/IX in chronic idiopathic thrombocytopenic purpura (ITP): evidence for at least two different IgG antibodies.
Antiplatelet antibodies in chronic idiopathic thrombocytopenic purpura (ITP) mainly target glycoprotein (GP) IIb/IIIa and GPIb/IX. Previous studies, employing modern antigen-specific assays, indicate that serum reactive with both GPIIb/IIIa and GPIb/IX is not an uncommon finding in chronic ITP. However, the mechanism behind this dual reactivity remains unclear. We studied sera from 72 patients with chronic ITP using modified GPIIb/IIIa- and GPIb/IX-specific MAIPA assays. Among the 34 positive sera, seven showed strong reactivity against both GPIIb/IIIa and GPIb/IX. These seven dual reactive ITP sera were further analysed by absorption studies. It was found that sera absorbed with immobilized GPIb/IX lost nearly all serum IgG specific for GPIb/IX but fully retained the IgG specific for GPIIb/IIIa. Conversely, sera absorbed with immobilized GPIIb/IIIa retained their reactivity only with GPIb/IX. These findings demonstrate that ITP sera, reactive with both GPIIb/IIIa and GPIb/IX, contain at least two different IgG antibody populations, each reactive with only one of the GP complexes.
Hou
M
M
Department of Medicine, Sahlgrenska University Hospital, Göteborg University, Sweden.
Stockelberg
D
D
Kutti
J
J
Wadenvik
H
H
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal / Q000276:immunology; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000276:immunology*; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000276:immunology*; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000276:immunology*
D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D019038:Platelet Glycoprotein GPIb-IX Complex