Fab-mediated binding of glycoprotein Ib/IX and IIb/IIIa specific antibodies in chronic idiopathic thrombocytopenic purpura.

• The antibody domain responsible for the interactions between platelet glycoproteins (GP) and serum IgG autoantibodies in patients with chronic idiopathic thrombocytopenic purpura (ITP) was studied. Sera from nine non-transfused ITP patients and 20 normal controls and a serum containing an anti-PlA1 antibody were employed. Serum, purified IgG and F(ab')2 fragments were prepared and their binding to platelet GPIb/IX and GPIIb/IIIa were analysed using a modified MAIPA assay and an antigen capture ELISA. In all experiments most of the autoantibodies studied behaved identically to the anti-PlA1 antibody in that the IgG-F(ab')2 fragments retained their ability to bind to the respective glycoprotein. Substituting the enzyme-conjugated secondary antibody (Fab specific), in the MAIPA assay, with an Fc specific antibody removed all reactivities observed against platelet GPs, produced by IgG-F(ab')2 fragments. Furthermore, in an antigen-capture ELISA, IgG autoantibodies against platelet GPIb/IX and/or GPIIb/IIIa were blocked preferentially by pre-incubating the ITP sera with a goat anti-human IgG (F(ab')2 specific) antibody, but not with an anti-Fc antibody. We conclude that these ITP patients produced antibodies specific for platelet GPIb/IX and/or GPIIb/IIIa, and that the autoantibody-platelet interaction was mediated by the classic Fab binding.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine (hsv//eng)

Nyckelord

Adult

Aged

Aged

80 and over

Autoantibodies

metabolism

Blood Platelets

metabolism

Chronic Disease

Electrophoresis

Polyacrylamide Gel

Enzyme-Linked Immunosorbent Assay

Female

Humans

Immunoglobulin Fab Fragments

isolation & purification

metabolism

Immunoglobulin G

isolation & purification

Immunologic Techniques

Male

Middle Aged

Platelet Glycoprotein GPIIb-IIIa Complex

metabolism

Platelet Glycoprotein GPIb-IX Complex

metabolism

Protein Binding

Purpura

Thrombocytopenic

Idiopathic

immunology

metabolism

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