Shayela Suvarna

Optimization of a murine immunization model for study of PF4/heparin antibodies.

Summary.  Background: Heparin‐induced thrombocytopenia (HIT) is a life‐threatening thrombotic illness caused by drug‐dependent antibodies recognizing complexes of platelet factor 4 (PF4) and heparin. Little is known about the immune pathogenesis of HIT, in particular factors influencing PF4/heparin antibody formation. To gain insight into the biologic basis of heparin sensitization, we have recently developed an animal model using wild‐type (WT) mice in which murine PF4/heparin antibodies (anti‐mPF4/H) arise de novo after antigen challenge. Objectives and methods: This report describes technical refinements to the murine model and describes additional biologic features of the immune response to mPF4/heparin. Results: Our studies indicate that antibody responses to mPF4/heparin are dependent on murine strain, injection routes and doses of mPF4 and heparin. C57BL/6 mice are more immunologically responsive to mPF4/heparin antigen than BALB/c mice and robust immunization can be achieved with intravenous, but not intraperitoneal, administration of antigen. We also observe a direct relationship between initial concentrations of mPF4 and antibody levels. Additionally, we demonstrate that mPF4/H immune response in mice decays with time, is not associated with thrombocytopenia and displays characteristics of immune recall on re‐exposure to antigen. Conclusions: These studies describe and characterize a murine model for studying the immunologic basis of PF4/heparin sensitization.

Platelet factor 4-heparin complexes trigger immune responses independently of the MyD88 pathway

Asher Winder Rafi Lefkowitz Hussam Ghoti Merav Leiba Tomas Ganz Elizabeta Nemeth Eliezer A. Rachmilewitz Department of Haematology, Wolfson Medical Centre, Holon, Israel, Department of Medicine and Pathology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA, and Department of Haematology, BMT & CBB, Sheba Medical Centre, Tel-Hashomer, Israel. E-mail: awinder@post.tau.ac.il

Influence of Sample Collection and Storage on the Detection of Platelet Factor 4–Heparin Antibodies

Heparin-induced thrombocytopenia is a life threatening thrombotic disorder caused by antibodies to platelet factor 4 (PF4) and heparin. Commercial immunoassays are frequently used for the detection of PF4-heparin antibodies, and several studies have reported that higher antibody titers are more frequently associated with adverse events. It is not known if conditions involving sample preparation and/or storage affect the operational characteristics of PF4-heparin immunoassays. We compared the detection of PF4-heparin antibodies from 48 patient samples collected concordantly in serum separator tubes or tubes containing EDTA or sodium citrate. We also examined the effects of extended sample storage on whole blood collected in serum separator, EDTA, or citrate tubes at 4 degrees C for up to 96 hours on antibody detection. We noted that serum or plasma anticoagulated with sodium citrate or EDTA yielded comparable results. In addition, we could not demonstrate any significant sample deterioration after storage at 4 degrees C in any medium for up to 4 days. These findings suggest that PF4-heparin antibodies are largely insensitive to the effects of sample preparation and storage.

Receptor-Signaling Pathways in Heart Failure

Heart failure, a progressive disorder characterized by deterioration of cardiac function and premature myocardial cell death, results from several common heart diseases such as coronary atherosclerosis, hypertension, and valvular diseases (1,2). With almost 550,000 new cases diagnosed each year, heart failure affects an estimated 4.7 million Americans, and costs associated with the disease range from

Protein Kinase A and G Protein-coupled Receptor Kinase Phosphorylation Mediates β-1 Adrenergic Receptor Endocytosis through Different Pathways

10 billion to

Determinants of PF4/heparin immunogenicity

40 billion per year (3). The aggregate 5-year mortality of patients with heart failure is about 50%, while the 1-year mortality of patients with advanced disease may exceed 50% (3). To maintain adequate myocardial contractility in response to injury, the heart uses several mechanisms, including hypertrophy of myocardial cells, changing the energetics of myocardial cell contraction, and upregulating transcription of several genes (4,5).