scholarly journals Anti-Platelet Factor 4/Heparin Antibody Formation Occurs Endogenously and at Unexpected High Frequency in Polycythemia Vera

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Sara C. Meyer ◽  
Eva Steinmann ◽  
Thomas Lehmann ◽  
Patricia Muesser ◽  
Jakob R. Passweg ◽  
...  
Keyword(s):  
High Frequency ◽  
Myeloproliferative Neoplasms ◽  
Platelet Factor 4 ◽  
Platelet Factor ◽  
Thrombotic Risk ◽  
Heparin Induced Thrombocytopenia ◽  
Disease Characteristics ◽  
Risk For Thrombosis ◽  
Validation Testing ◽  
Heparin Exposure

Background.Myeloproliferative neoplasms (MPN) encounter thromboses due to multiple known risk factors. Heparin-induced thrombocytopenia (HIT) is a thrombotic syndrome mediated by anti-platelet factor 4 (PF4)/heparin antibodies with undetermined significance for thrombosis in MPN. We hypothesized that anti-PF4/heparin Ab might occur in MPN and promote thrombosis.Methods.Anti-PF4/heparin antibodies were analyzed in 127 MPN patients including 76 PV and 51 ET. Screening, validation testing, and isotype testing of anti-PF4/heparin Ab were correlated with disease characteristics.Results.Anti-PF4/heparin antibodies were detected in 21% of PV and 12% of ET versus 0.3–3% in heparin-exposed patients. Validation testing confirmed anti-PF4/heparin immunoglobulins in 15% of PV and 10% of ET. Isotype testing detected 9.2% IgG and 5.3% IgM in PV and exclusively IgM in ET. IgG-positive PV patients encountered thromboses in 57.1% suggesting anti-PF4/heparin IgG may contribute to higher risk for thrombosis in MPN. Overall, 45% of PV patients experienced thromboses with 11.8% positive for anti-PF4/heparin IgG versus 7.1% in PV without thrombosis.Conclusion.Anti-PF4/heparin antibodies occur endogenously and more frequently in MPN than upon heparin exposure. Thrombotic risk increases in anti-PF4/heparin IgG-positive PV reflecting potential implications and calling for larger, confirmatory cohorts. Anti-PF4/heparin IgG should be assessed upon thrombosis in PV to facilitate avoidance of heparin in anti-PF4/heparin IgG-positive PV.

Prevalence of Heparin Antibodies in ICU Patients (The HAICU Study).

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 4011-4011
Author(s):  
Georgene W. Hergenroeder ◽  
John L. Francis ◽  
Charles C. Miller ◽  
Robert L. Levine
Keyword(s):  
Serotonin Release ◽  
Convenience Sample ◽  
Platelet Factor ◽  
Icu Patients ◽  
Heparin Induced Thrombocytopenia ◽  
Icu Admission ◽  
Release Assay ◽  
Risk For Thrombosis ◽  
New Onset ◽  
Heparin Exposure

Abstract BACKGROUND: Heparin-induced thrombocytopenia (HIT) is an antibody-mediated prothrombotic disorder characterized by absolute or relative thrombocytopenia occurring after exposure to heparin. Although thrombocytopenia in HIT patients usually resolves after discontinuing heparin, the risk for thrombosis persists up to 3 months. PURPOSE: The HAICU study was conducted to determine the prevalence of heparin-induced antibodies and HIT on admission to the intensive care unit (ICU) and their development within a week of hospitalization. METHODS: Platelet counts and heparin-platelet factor 4 antibodies (GTI ELISA) were measured on admission and again on day 7 ± 2 or discharge on a convenience sample of ICU patients. Patients with new onset thrombocytopenia (unexplained platelet count <100 x109/L or a 50% decrease in count) or a positive ELISA had confirmatory testing for HIT antibodies using a serotonin release assay. HIT was prospectively defined as positive HIT antibodies by both assays or as HIT antibodies with new onset, unexplained thrombocytopenia. RESULTS: Over 6 months, 118 patients were enrolled from three ICUs. Subjects had an average ICU LOS of 9 +/− 11 days, hospital LOS of 20 +/− 11 days and Apache II Physiology Score of 14 +/− 7; 59% were male. HIT, as defined above, occurred in 3 (3%) patients on admission. After 7.2 ± 2 days, HIT occurred in an additional 9 patients. Overall, 12 of 118 (10%) ICU patients had HIT at or within a week of admission (Table 1). 5 had documented prior exposure to heparin within 100 days of ICU admission, and 4 received heparin during the period when HIT assays were performed. Cases were distributed throughout the ICU’s, yet relatively more often in the neurotrauma and shock-trauma units than the medical unit. CONCLUSION: Heparin-induced antibodies and HIT are common in the ICU, occurring in 3% of patients on admission and 10% in the first week. Physicians need to be aware of heparin exposure and the possibility of HIT in this population. Patients Positive for Heparin Antibodies by Type of ICU and Time Point Unit No. of Patients Percent (%) Day of ICU Admission Day 7 +/− 2 TOTAL Percent Positive per ICU (%) NTICU 56 47.5 1 5 6 11 STICU 39 33 2 3 5 13 MICU 23 19.5 0 1 1 4 TOTAL 118 100 3 9 12 10

Monocytes Are a Particularly Favorable Target for Surface Platelet Factor 4 (PF4) Antigenic Complex Formation in Heparin-Induced Thrombocytopenia: New Insights into the Thrombotic Risk in HIT

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 271-271
Author(s):  
Lubica Rauova ◽  
Gowthami M Arepally ◽  
Douglas B. Cines ◽  
Mortimer Poncz
Keyword(s):  
Complex Formation ◽  
Platelet Factor 4 ◽  
Drug Induced ◽  
Platelet Factor ◽  
Platelet Surface ◽  
Thrombotic Risk ◽  
Heparin Induced Thrombocytopenia ◽  
Antigenic Complex

Abstract Monocytes are a Favored Target for Surface Platelet Factor 4 (PF4) Antigenic Complex Formation in Heparin-Induced Thrombocytopenia: New Insights into the Thrombotic Risk in HIT Lubica Rauova, Gowthami Arepally, Douglas Cines and Mortimer Poncz HIT is a drug-induced autoimmune thrombocytopenia caused by antibodies to heparin/PF4 complexes that predispose to thrombotic complications. The studies described below examine how monocytes (Mo) may contribute to the thrombotic risk. We demonstrated previously that glycosaminoglycans (GAG) on the surface of platelets bind PF4, forming complexes that are recognized by HIT antibody, leading to platelet activation via the platelet FcγRIIA receptor in vitro and thrombocytopenia/thrombosis in vivo. However, heparin not only induces antibodies to develop against the PF4/GAG surface antigenic complexes, but also rapidly removes the same PF4/GAG complexes from the platelet surface, which may limit the likelihood of developing HIT and help limit its duration. This led us to study the involvement of Mo, which are a rich potential source of tissue factor and are known to be activated in HIT. Moreover, unlike platelets, which are coated with GAG composed almost entirely of chrondroitin sulfate (CS), Mo also express heparan sulfate, which has the capacity to bind PF4 with greater avidity and be resistant to the effect of plasma heparin. We found that Mo bind PF4 with greater avidity than platelets and higher concentrations of UFH are needed to remove PF4/GAG complexes and reduce the binding of a HIT monoclonal antibody KKO. In contrast to platelets, dissociation of PF4/GAG complexes from monocytes requires heparinases in addition to chondroitinases. In addition, macrophages GAG undergo hypersulfation during inflammation. Because clinical studies have shown inflammation predisposes to HIT, we examined the binding of KKO to unstimulated and bacterial lipopolysaccharide (LPS, E. coli serotype 011) stimulated cultured macrophages. Macrophages were derived from primary human Mo or murine bone marrow, cultured in the presence of M-CSF and stimulated with 0–500 ng/mL of LPS for 72 hrs. LPS increased KKO binding in the presence of PF4 2.7±0.7-fold compared to unstimulated cells (p<0.002) and the stimulated cells required ~2-fold higher concentrations of heparin to remove surface PF4/GAG complexes. Addition of [35S]sulfate during the last 24 hrs of incubation lead to a 4.1±0.1-fold increase in the incorporation of 35S into surface GAG after LPS stimulation (p<0.0001). These results provide important insights into the potential role of Mo in the prothrombotic sequelae of HIT. Compared to platelets, Mo are relatively resistant to “antigen down-regulation” by heparin and are more likely to bind anti-PF4/GAG HIT antibodies and become activated. The relative resistance of Mo to the dissociation PF4/GAG complexes from the cell surface also suggest a role in the development of Delayed-Onset HIT after heparin withdrawal.

Prevalence, isotype, and functionality of antiheparin–platelet factor 4 antibodies in patients treated with heparin and clinically suspected for heparin-induced thrombocytopenia

2002 ◽  
Vol 105 (2) ◽  
pp. 117-123 ◽  
Author(s):  
Brian Untch ◽  
Sarfraz Ahmad ◽  
Walter P. Jeske ◽  
Harry L. Messmore ◽  
Debra A. Hoppensteadt ◽  
...  
Keyword(s):  
Platelet Factor 4 ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia

scholarly journals Heparin-induced thrombocytopenia: in vitro studies on the interaction of dabigatran, rivaroxaban, and low-sulfated heparin, with platelet factor 4 and anti-PF4/heparin antibodies

Blood ◽  
2012 ◽  
Vol 119 (5) ◽  
pp. 1248-1255 ◽  
Author(s):  
Krystin Krauel ◽  
Christine Hackbarth ◽  
Birgitt Fürll ◽  
Andreas Greinacher
Keyword(s):  
Factor Xa ◽  
Platelet Factor 4 ◽  
Thrombin Inhibitors ◽  
Direct Thrombin Inhibitors ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Alternative Anticoagulation ◽  
Heparin Complexes ◽  
History Of

Abstract Heparin is a widely used anticoagulant. Because of its negative charge, it forms complexes with positively charged platelet factor 4 (PF4). This can induce anti-PF4/heparin IgG Abs. Resulting immune complexes activate platelets, leading to the prothrombotic adverse drug reaction heparin-induced thrombocytopenia (HIT). HIT requires treatment with alternative anticoagulants. Approved for HIT are 2 direct thrombin inhibitors (DTI; lepirudin, argatroban) and danaparoid. They are niche products with limitations. We assessed the effects of the DTI dabigatran, the direct factor Xa-inhibitor rivaroxaban, and of 2-O, 3-O desulfated heparin (ODSH; a partially desulfated heparin with minimal anticoagulant effects) on PF4/heparin complexes and the interaction of anti-PF4/heparin Abs with platelets. Neither dabigatran nor rivaroxaban had any effect on the interaction of PF4 or anti-PF4/heparin Abs with platelets. In contrast, ODSH inhibited PF4 binding to gel-filtered platelets, displaced PF4 from a PF4-transfected cell line, displaced PF4/heparin complexes from platelet surfaces, and inhibited anti-PF4/heparin Ab binding to PF4/heparin complexes and subsequent platelet activation. Dabigatran and rivaroxaban seem to be options for alternative anticoagulation in patients with a history of HIT. ODSH prevents formation of immunogenic PF4/heparin complexes, and, when given together with heparin, may have the potential to reduce the risk for HIT during treatment with heparin.

Pathophysiology of Heparin-Induced Thrombocytopenia

2000 ◽  
Vol 124 (11) ◽  
pp. 1657-1666 ◽  
Author(s):  
Fabrizio Fabris ◽  
Sarfraz Ahmad ◽  
Giuseppe Cella ◽  
Walter P. Jeske ◽  
Jeanine M. Walenga ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Serotonin Release ◽  
Platelet Factor 4 ◽  
Thrombin Inhibitors ◽  
Platelet Factor ◽  
Cellular Activation ◽  
Heparin Induced Thrombocytopenia ◽  
New Information ◽  
Study Selection ◽  
Release Assay

Abstract Objective.—This review of heparin-induced thrombocytopenia (HIT), the most frequent and dangerous side effect of heparin exposure, covers the epidemiology, pathophysiology, clinical presentation, diagnosis, and treatment of this disease syndrome. Data Sources and Study Selection.—Current consensus of opinion is given based on literature reports, as well as new information where available. A comprehensive analysis of the reasons for discrepancies in incidence numbers is given. The currently known mechanism is that HIT is mediated by an antibody to the complex of heparin–platelet factor 4, which binds to the Fc receptor on platelets. New evidence suggests a functional heterogeneity in the anti-heparin-platelet factor 4 antibodies generated to heparin, and a “superactive” heparin-platelet factor 4 antibody that does not require the presence of heparin to promote platelet activation or aggregation has been identified. Up-regulation of cell adhesion molecules and inflammatory markers, as well as preactivation of platelets/endothelial cells/leukocytes, are also considered to be related to the pathophysiology of HIT. Issues related to the specificity of currently available and new laboratory assays that support a clinical diagnosis are addressed in relation to the serotonin-release assay. Past experience with various anticoagulant treatments is reviewed with a focus on the recent successes of thrombin inhibitors and platelet GPIIb/IIIa inhibitors to combat the platelet activation and severe thrombotic episodes associated with HIT. Conclusions.—The pathophysiology of HIT is multifactorial. However, the primary factor in the mediation of the cellular activation is due to the generation of an antibody to the heparin-platelet factor 4 complex. This review is written as a reference for HIT research.

scholarly journals Platelet Activation in Heparin-Induced Thrombocytopenia is Followed by Platelet Death via Complex Apoptotic and Non-Apoptotic Pathways

2020 ◽  
Vol 21 (7) ◽  
pp. 2556
Author(s):  
Elmira R. Mordakhanova ◽  
Tatiana A. Nevzorova ◽  
Gulnaz E. Synbulatova ◽  
Lubica Rauova ◽  
John W. Weisel ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Immune Complexes ◽  
Gel Filtration ◽  
Human Platelets ◽  
Platelet Factor 4 ◽  
Platelet Factor ◽  
Heparin Induced Thrombocytopenia ◽  
Mitochondrial Membrane Depolarization ◽  
Low Platelet Count ◽  
Apoptotic Pathways

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction characterized by thrombocytopenia and a high risk for venous or arterial thrombosis. HIT is caused by antibodies that recognize complexes of platelet factor 4 and heparin. The pathogenic mechanisms of this condition are not fully understood. In this study, we used flow cytometry, fluorimetry, and Western blot analysis to study the direct effects of pathogenic immune complexes containing platelet factor 4 on human platelets isolated by gel-filtration. HIT-like pathogenic immune complexes initially caused pronounced activation of platelets detected by an increased expression of phosphatidylserine and P-selectin. This activation was mediated either directly through the FcγRIIA receptors or indirectly via protease-activated receptor 1 (PAR1) receptors due to thrombin generated on or near the surface of activated platelets. The immune activation was later followed by the biochemical signs of cell death, such as mitochondrial membrane depolarization, up-regulation of Bax, down-regulation of Bcl-XL, and moderate activation of procaspase 3 and increased calpain activity. The results show that platelet activation under the action of HIT-like immune complexes is accompanied by their death through complex apoptotic and calpain-dependent non-apoptotic pathways that may underlie the low platelet count in HIT.

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