Antiplatelet Glycoprotein Complex-dependent Autoantibodies Impair Platelet Function in Chronic Immune...

Platelet membrane glycoproteins (GPs) serve as key autoantigens in immune thrombocytopenia (ITP). Autoantibodies target linear or conformational epitopes of intact GP complexes, yet the distinct contributions in platelet injury remain unclear.

To determine how GP-complex-dependent and GP-complex-independent autoantibodies affect platelet aggregation, activation, apoptosis and desialylation in chronic ITP, and to assess their associations with clinical bleeding.

Serum anti-GP antibodies from 130 patients with chronic ITP were measured using an indirect flow cytometry microbeads assay. Sodium dodecyl sulfate (SDS)-mediated denaturation of GP complexes was used to distinguish the two antibody subtypes. Platelet aggregation, activation, apoptosis and desialylation were assessed by microaggregation, CD62P expression, mitochondrial membrane potential, and lectin-binding assays, respectively.

Anti-GPIIb/IIIa and anti-GPIb/IX antibodies were detected against native antigens in 40 (30.77%) and 17 (13.08%) patients, respectively. Following SDS treatment, antibody reactivity was abolished in 13 and 2 patients respectively, indicating exclusively GP-complex-dependent antibodies. Patients with complex-dependent antibodies exhibited markedly impaired platelet aggregation. Sera from patients with impaired aggregation induced lower CD62P expression in donor platelets (P=0.0323), whereas platelet desialylation and apoptosis did not differ significantly between groups. Antibodies associated with impaired platelet aggregation were also linked to higher Skin, visible Mucosae, Organs, and Gradation of Severity (SMOG) bleeding index (P<0.001).

GP-complex-dependent and -independent autoantibodies represent functionally distinct antibody profiles in chronic ITP. Complex-dependent autoantibodies significantly impaired platelet aggregation, and patients harboring these functionally active antibodies exhibited more severe bleeding-related symptoms. Functional antibody characterization may improve bleeding-risk assessment and support more individualized management.