Target antigens of anti-platelet antibodies in patients with steroid-resistant ITP of recent onset. Canadian Apheresis Study Group.
Recent application of Western blotting procedures in the detection of anti-platelet antibodies has permitted more refined definition of reactivity. We report on the results of anti-platelet antibody assays in a series of 19 patients with recently diagnosed (less than 6 months duration) steroid-resistant, idiopathic thrombocytopenia purpura (ITP). At presentation, six of the 19 patients had a positive test for platelet-associated IgG (PAIgG) as measured by the direct radial-immunodiffusion (RID) assay, whereas three of the 19 were positive with the direct-platelet-suspension-immunofluorescence test (DPSIFT). The indirect-platelet-suspension-immunofluorescence test (IPSIFT) demonstrated antibodies in seven of the sera. Following Western blot (WB) analysis, the serum of 7/19 patients (only three of which were positive in the IPSIFT) could be shown to react with platelet antigens. Two patterns were seen: in four cases there were bands of apparent molecular weights of 60,000, 55,000 and 50,000; in the other three samples, a single band near 90,000 was demonstrated. Unlike the situation reported for chronic ITP, no reactivity was seen against higher molecular weight antigens other than the 'non-specific' binding at apparent molecular weight 200,000 which is also seen with normal sera. The data suggest that antibodies reacting against specific platelet antigens are present in the serum of some patients with recent onset ITP.
Rock
G
G
Department of Medicine, University of Ottawa, ON, Canada.
Buskard
N
N
Leblond
P
P
Shumak
K
K
Sutton
D
D
Hashemi
S
S
D000328:Adult; D000368:Aged; D000918:Antibody Specificity; D016824:Antigens, Human Platelet / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology; D001327:Autoimmune Diseases / Q000188:drug therapy / Q000276:immunology*; D015153:Blotting, Western; D004351:Drug Resistance; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D008875:Middle Aged; D008970:Molecular Weight; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000188:drug therapy / Q000276:immunology*; D013997:Time Factors
D016824:Antigens, Human Platelet; D001323:Autoantibodies; D001324:Autoantigens; D007074:Immunoglobulin G