Intravenous immunoglobulin prevents thrombosis in an endothelialized disease model of heparin-induced thrombocytopenia.

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is a serious adverse reaction to heparin, associated with increased risk of thromboembolic complications. Intravenous immunoglobulins (IVIGs) have been used as a therapeutic for HIT and are believed to alleviate thrombocytopenia and reduce thrombosis risk. Yet the antithrombotic effects of IVIG in HIT remain underexplored.

OBJECTIVE

To investigate the effect of IVIG on thrombus formation in an ex vivo model of HIT-IgG-induced thrombosis.

METHODS

Microfluidic channels were coated with a confluent monolayer of human umbilical vein endothelial cells that were primed with TNF-α to induce an activated, inflammatory state. Whole blood was exposed to unfractionated heparin, with or without IVIG before subjecting to treatment with a monoclonal HIT-like antibody (K070), or HIT-patient-IgG. Recalcified blood was perfused over human umbilical vein endothelial cells at venous shear stress. Thrombus structure and dynamics were investigated by immunofluorescence microscopy.

RESULTS

HIT-patient-IgGs and K070 induced thrombus formation in the presence of prophylactic heparin exposure, over TNF-α treated, inflamed endothelial cells. HIT thrombi were enriched in fibrin, phosphatidylserine-bearing platelets, and leukocyte aggregates. We observed thrombi being formed on adherent platelets, which gradually recruited leukocytes into a three-dimensional thrombus structure. Pretreatment of blood with IVIG significantly reduced cellular adhesions and prevented thrombus formation.

CONCLUSION

Our endothelialized ex vivo flow chamber system effectively recapitulates the immunothrombotic phenotype of HIT and offers a reliable tool to urgently validate the efficacy of IVIG intervention against HIT-IgG-induced thrombosis in patients.