Heparin-induced thrombocytopenia (HIT) is an antibody-mediated complication of heparin treatment that can lead to thrombosis and thromboembolism. HIT is mainly caused by immunoglobulin G (IgG) class among anti-heparin/platelet factor 4 antibodies that bind to epitopes on platelet factor 4 (PF4) released from activated platelets that developed when it forms complexes with heparin. Platelet aggregation and hypercoagulation status result from this process. Besides, the reactions between antibodies and vascular endothelial cells and monocytes are involved in HIT. Laboratory detection of anti-heparin/platelet factor 4 antibodies after heparin administration may help diagnose HIT early. Tests for detecting antibodies to the heparin/PF4 complex can be classified into functional platelet assays (which rely on the demonstration of platelet activation) and immunoassays (which detect the presence of an antibody without regard for its functional ability). But there is no simple and effective test available currently. In this article the anti-heparin/platelet factor 4 antibodies, pathogenesis of HIT, clinical laboratory assays and immunoassays are reviewed.
Antigen-Antibody Complex ; immunology ; Heparin ; adverse effects ; immunology ; Humans ; Immunoglobulin G ; immunology ; Platelet Aggregation ; Platelet Factor 4 ; immunology ; Thrombocytopenia ; chemically induced ; immunology

Aged ; Cross Reactions ; Female ; Heparin ; adverse effects ; immunology ; Heparin, Low-Molecular-Weight ; adverse effects ; immunology ; Humans ; Male ; Middle Aged ; Platelet Factor 4 ; immunology ; Thrombocytopenia ; blood ; chemically induced ; immunology

OBJECTIVETo study the effect of PF4 on the adherence of leukemic CD34+ KG1a cell to human umbilical vein endothelial cell line ECV-304 cell and on the expression of adhesive molecules.

METHODSAdhesion assay and adhesion blocking assay were respectively applied to measure the effect of PF4 and/or adhesion molecule monoclonal antibodies on the adhesion property of KG1a. The expressions of adhesion molecules were determined by RT-PCR and FACS analysis.

RESULTSThe adhesion of KG1a cells to ECV-304 was significantly enhanced in the presence of PF4. Such enhancement was also observed when KG1a or ECV-304 cells were separately treated with PF4 before interaction. The adhesion capacity of KG1a cells was reduced when cells were co-incubated with the blocking monoclonal antibodies (MoAbs) against CD49d, CD106, CD54, respectively. In contrast, MoAbs against CD62L, CD62P and CD62E had no such effect. During a period of 3 hours when KG1a or ECV-304 cells were respectively incubated with PF4, the mRNA expressions of CD49 d, CD54 were up-regulated. Furthermore, when KG1a or ECV-304 cells were incubated with PF4 for 2 hours, respectively, the percentages of CD49d+ KG1a cells and CD54+ ECV-304 were increased significantly.

CONCLUSIONPF4 can enhance KG1a cell adhesive capacity by increasing the expressions of adhesion molecules.

Antigens, CD34 ; metabolism ; Cell Adhesion ; drug effects ; Cell Adhesion Molecules ; metabolism ; Cell Line, Tumor ; Humans ; Leukemia, Myeloid, Acute ; immunology ; pathology ; Platelet Factor 4 ; pharmacology ; Umbilical Veins ; cytology

To investigate the effects of stromal cell-derived factor 1 (SDF-1) and platelet factor 4 (PF4) on the homing-related function of expanded ex vivo umbilical cord blood CD34(+) cells, purified cord blood CD34(+) cells were cultured in serum-free medium containing a HGF combination of FL + SCF + TPO (FST) with either 100 ng/ml SDF-1 alone, 100 ng/ml PF4 alone, or both of these 2 cytokines. The expansion rate of CD34(+) cells, colony formation, homing-related functions including expression of homing-related adhesion molecules of expanded CD34(+) cell, adhesion activity and chemotactic function of the re-selected expanded CD34(+) cells were evaluated at different time points. The results showed that expansion rate of CD34(+) cells and expansion multiple of CFU in SDF-1 groups were higher than those in control. The expression of CD49e on the expanded CD34(+) cells was remarkable up-regulated, in contrast, expression of CXCR-4 on the expanded CD34(+) cells was remarkable down-regulated in SDF-1 groups. The expression of CD49e, CD54 and CXCR-4 on the expanded CD34(+) cells were remarkably up-regulated in the PF4 groups. In all the SDF-1 group, PF4 group and SDF-1 plus PF4 group, the ability of expanded CD34(+) cells adhering to fibronectin layer were higher than those in the control on day 10. Spontaneous migration rate of expanded CD34(+) cells in SDF-1 groups were higher than those in control, while SDF-1-induced migration rate were lower than those in control on day 10. SDF-1-induced migration rate in PF4 groups were higher than those in control on day 10. Spontaneous and SDF-1-induced migration rate of expanded CD34(+) cells in the SDF-1 plus PF4 groups were higher than those in control on day 10. It is concluded that, SDF-1 and PF4 can up-regulate expression of adhesion molecules on expanded CD34(+) cells, and retain the adherent and migration ability of expanded CD34(+) cells, which is helpful for the homing of expanded CD34(+) cells. In short, SDF-1 and PF4 are helpful for the homing-related function of the expanded UCB HSPC.
Antigens, CD34 ; blood ; immunology ; Cell Adhesion ; drug effects ; Cells, Cultured ; Chemokine CXCL12 ; Chemokines, CXC ; pharmacology ; Chemotaxis ; immunology ; physiology ; Culture Media, Serum-Free ; Fetal Blood ; cytology ; immunology ; Hematopoietic Stem Cells ; cytology ; drug effects ; Humans ; Platelet Factor 4 ; pharmacology

Since heparin is an anticoagulant commonly used in hemodialysis and the patients on hemodialysis are repeatedly exposed to heparin, heparin may be the cause of the development of heparin-dependent antibodies and thrombotic complications in patients on hemodialysis. The purpose of this study was to determine the prevalence and the clinical significance of the antibodies against heparin-platelet factor 4 complexes as determined by enzyme immunoassay in patients on maintenance hemodialysis. The prevalence of anti-heparin-platelet factor 4 antibodies was higher in hemodialysis patients than in normal subjects (8.8 vs 0.0%, p<0.05). The number of past episodes of vascular access obstruction per year was significantly higher in the anti-heparin-platelet factor 4 antibody positive group than antibody negative group. Anti-heparin-platelet factor 4 antibody positive patients experienced more frequent vascular access obstructions than control subjects. In conclusion, anti-heparin-platelet factor 4 antibody might be a risk factor for vascular access obstructions in patients with end-stage renal disease on maintenance hemodialysis.
Adult ; Autoantibodies/immunology* ; Autoimmune Diseases/immunology* ; Catheters, Indwelling* ; Enzyme-Linked Immunosorbent Assay ; Female ; Heparin/immunology* ; Human ; Kidney Failure, Chronic/blood ; Kidney Failure, Chronic/immunology ; Kidney Failure, Chronic/therapy* ; Male ; Middle Aged ; Platelet Factor 4/immunology* ; Recurrence ; Renal Dialysis* ; Risk Factors ; Thrombophilia/immunology* ; Thrombosis/epidemiology* ; Thrombosis/immunology ; Thrombosis/prevention & control

BACKGROUND: Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction caused by antibodies to the heparin/platelet factor 4 (PF4) complex, resulting in thrombocytopenia and prothrombotic state. HIT diagnosis is challenging and depends on clinical presentation and laboratory tests. We investigated the usefulness of clinical scores and heparin/PF4 ELISA optical density (OD) as a diagnostic marker and thrombosis predictor in HIT. METHODS: We analyzed 92 patients with suspected HIT. The heparin/PF4 antibody was measured using a commercial ELISA kit (GTI, USA). For each patient, the 4 T's score and Chong's score were calculated. RESULTS: Of the 92 patients, 28 were anti-heparin/PF4-seropositive. The 4 T's score and Chong's score showed good correlation (r=0.874). The 4 T's score and OD values showed good performance for diagnosis of the definite and unlikely HIT groups; however, OD levels showed better sensitivity (93.8%) than the 4 T's score used alone (62.5%). Of the 92 patients, 26 developed thrombosis. The OD values were significantly higher in patients with thrombosis than in those without thrombosis (0.52 vs. 0.22, P<0.001). Patients with high OD values (OD>0.4) had an increased risk of thrombosis (adjusted odds ratio 9.44 [3.35-26.6], P<0.001) and a shorter 250-day thrombosis-free survival (32.1% vs. 54.7%, P=0.012). CONCLUSIONS: ELISA OD values in combination with clinical scoring can improve the diagnosis of and thrombosis prediction in HIT. More attention should be paid to the use of clinical scores and OD values as thrombosis predictors in HIT.
Adolescent ; Adult ; Aged ; Aged, 80 and over ; Antibodies/adverse effects/analysis ; Area Under Curve ; Child ; Child, Preschool ; Enzyme-Linked Immunosorbent Assay/*methods ; Female ; Heparin/immunology ; Humans ; Infant ; Male ; Middle Aged ; Platelet Factor 4/immunology ; Risk ; Sensitivity and Specificity ; Survival Analysis ; Thrombocytopenia/chemically induced/*diagnosis/mortality ; Thrombosis/*diagnosis/etiology

This study was designed to investigate the incidence, causes, and outcomes of new-onset thrombocytopenia (NOT) in Korean intensive care units (ICUs). A prospective cohort study was conducted in medical ICUs of Samsung Medical Center between August 2010 and February 2011. All newly admitted patients were included if they stayed in the ICU for more than 48 hr and did not have thrombocytopenia upon admission. A total of 186 patients were included. NOT developed in 37.1%. Most common cause of NOT was sepsis with disseminated intravascular coagulation (66.7%), followed by drug-induced thrombocytopenia (18.8%), and heparin-induced thrombocytopenia (2.9%). IgG-specific antibody to platelet factor 4/heparin was positive in 2.4% among patients treated with heparin, and thrombosis occurred in two patients. Twenty eight-day mortality was higher in patients that developed NOT compared to those that did not develop NOT (39.1% vs 12%, P < 0.001). NOT increased the odds ratio of 28-day mortality and was an independent risk factor for mortality (OR 3.52; 95% CI 1.32-9.38; P = 0.012). In conclusion, NOT is common and is an independent risk factor for mortality in Korean ICU patients. Therefore, clinicians should make every effort to correct the causes of NOT.
Aged ; Cohort Studies ; Disseminated Intravascular Coagulation/complications ; Female ; Heparin/immunology ; Hospitals ; Humans ; Immunoglobulin G/blood ; Incidence ; Intensive Care Units ; Male ; Middle Aged ; Odds Ratio ; Platelet Factor 4/immunology ; Prognosis ; Prospective Studies ; Republic of Korea ; Risk Factors ; Sepsis/complications ; Survival Analysis ; Thrombocytopenia/*epidemiology/etiology/mortality ; Thrombosis/etiology

This study was designed to investigate the incidence, causes, and outcomes of new-onset thrombocytopenia (NOT) in Korean intensive care units (ICUs). A prospective cohort study was conducted in medical ICUs of Samsung Medical Center between August 2010 and February 2011. All newly admitted patients were included if they stayed in the ICU for more than 48 hr and did not have thrombocytopenia upon admission. A total of 186 patients were included. NOT developed in 37.1%. Most common cause of NOT was sepsis with disseminated intravascular coagulation (66.7%), followed by drug-induced thrombocytopenia (18.8%), and heparin-induced thrombocytopenia (2.9%). IgG-specific antibody to platelet factor 4/heparin was positive in 2.4% among patients treated with heparin, and thrombosis occurred in two patients. Twenty eight-day mortality was higher in patients that developed NOT compared to those that did not develop NOT (39.1% vs 12%, P < 0.001). NOT increased the odds ratio of 28-day mortality and was an independent risk factor for mortality (OR 3.52; 95% CI 1.32-9.38; P = 0.012). In conclusion, NOT is common and is an independent risk factor for mortality in Korean ICU patients. Therefore, clinicians should make every effort to correct the causes of NOT.
Aged ; Cohort Studies ; Disseminated Intravascular Coagulation/complications ; Female ; Heparin/immunology ; Hospitals ; Humans ; Immunoglobulin G/blood ; Incidence ; Intensive Care Units ; Male ; Middle Aged ; Odds Ratio ; Platelet Factor 4/immunology ; Prognosis ; Prospective Studies ; Republic of Korea ; Risk Factors ; Sepsis/complications ; Survival Analysis ; Thrombocytopenia/*epidemiology/etiology/mortality ; Thrombosis/etiology