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Heparin-independent, PF4-dependent binding of HIT antibodies to platelets: implications for HIT pathogenesis. Blood 2015 Jan 01;125(1):155-61 PMID: 25342714 PMCID: PMC4281824

Pubmed ID





Antibodies specific for platelet factor 4 (PF4)/heparin complexes are the hallmark of heparin-induced thrombocytopenia and thrombosis (HIT), but many antibody-positive patients have normal platelet counts. The basis for this is not fully understood, but it is believed that antibodies testing positive in the serotonin release assay (SRA) are the most likely to cause disease. We addressed this issue by characterizing PF4-dependent binding of HIT antibodies to intact platelets and found that most antibodies testing positive in the SRA, but none of those testing negative, bind to and activate platelets when PF4 is present without any requirement for heparin (P < .0001). Binding of SRA-positive antibodies to platelets was inhibited by chondroitinase ABC digestion (P < .05) and by the addition of chondroitin-4-sulfate (CS) or heparin in excess quantities. The findings suggest that although all HIT antibodies recognize PF4 in a complex with heparin, only a subset of these antibodies recognize more subtle epitopes induced in PF4 when it binds to CS, the major platelet glycosaminoglycan. Antibodies having this property could explain "delayed HIT" seen in some individuals after discontinuation of heparin and the high risk for thrombosis that persists for weeks in patients recovered from HIT.

Author List

Padmanabhan A, Jones CG, Bougie DW, Curtis BR, McFarland JG, Wang D, Aster RH


Richard H. Aster MD Professor in the Medicine department at Medical College of Wisconsin
Brian Curtis PhD Director in the Platelet & Neutrophil Immunology Laboratory department at BloodCenter of Wisconsin
Anand Padmanabhan MD, PhD Associate Professor in the Pathology department at Medical College of Wisconsin
Demin Wang PhD Assistant Professor in the Microbiology and Immunology department at Medical College of Wisconsin


2-s2.0-84920555104   31 Citations

MESH terms used to index this publication - Major topics in bold

Blood Platelets
Chondroitin Sulfates
Enzyme-Linked Immunosorbent Assay
Immunoglobulin G
Platelet Activation
Platelet Factor 4
Protein Binding
jenkins-FCD Prod-353 9ccd8489072cb19f5b9f808bb23ed672c582f41e