Platelet-Derived Microparticles Bearing PF4 and Anti-GAGS Immunoglobulins in Patients with Sepsis.

PF4 is a megakaryocyte-derived cationic chemokine that plays a part in innate immunity through its activity on the macrophages. In bacterial sepsis, PF4 binds to glycosaminoglycans (GAGs) on the surface of aerobic bacteria, giving rise to an antigenic complex that induces the early formation of anti-PF4 IgG-IgA-IgM. This triggers the immune response in patients receiving heparin therapy who develop heparin-induced thrombocytopenia (HIT). These antibodies have also been identified in patients with chronic Gram-negative infections. Given the complexity of this innate immune response network, our study on 45 patients with sepsis focused on the immune response mediated by platelet PF4. We analyzed the role of IgG-IgA-IgM against PF4-GAGs, and the presence of specific PF4-bearing platelet microparticles (PMPs). Anti-GAGs/PF4 IgG-IgA-IgM levels were significantly higher in septic patients than in control groups (healthy controls or acute patients without sepsis, p < 0.001). PF4-bearing PMP levels were only significantly higher in septic patients (p < 0.001). The occurrence of IgG-IgA-IgM against PF4-GAGs and PF4+ PMPs correlated with an improvement in patients' sepsis. In conclusion, we demonstrated that, in the course of bacterial sepsis, platelet activation leads to the formation of specific PF4-bearing PMPs. These specific microparticles bind to polyanionic sequences on the surface of aerobic bacteria, giving rise to an antigenic complex that induces the early formation of IgG-IgA-IgM against PF4-GAGs as an innate immune response to infection.

Short-term exposure to high levels of air pollution as a risk factor for acute isolated pulmonary embolism.

BACKGROUND: The association between air pollution exposure and occurrence of venous thromboembolism is a matter of debate. This retrospective case-control study investigated the associations between one month's exposure to elevated levels of different pollutants (i.e. PM10, CO, NOx, O3, SO2, Benzene, Benzoapyrene, Nickel, Lead Arsenic) and the development of acute isolated pulmonary embolism (PE). METHODS: The cases included 33 patients consecutively admitted to Padua Hospital with an objectively proven diagnosis of acute unprovoked (i.e. without predisposing conditions) isolated (i.e. without deep vein thrombosis) PE. The control group consisted of 72 consecutive patients with objectively proven acute provoked (i.e. associated to predisposing conditions) isolated PE. Average mean concentrations of pollutants in the month before PE diagnosis were computed by monitors located at 2 different sites throughout the city of Padua, and were obtained from the Regional Agency for Environmental Protection. RESULTS: Individuals who had PM10, NOx, Benzene, Benzoapyrene, Cadmium, and Lead exposure equal/above the 2nd tertile, measured in controls, showed a significant increase in the risk of unprovoked PE. In case of PM10 and Benzoapyrene this risk was not affected after adjustment for possible confounders. In fact, in the multivariate logistic regression analysis, the OR values were 5.24 (95% CI: 1.52-18.12) for PM10 and 3.95 (95% CI: 1.06-14.71) for Benzoapyrene exposure in the month before PE diagnosis. CONCLUSIONS: Our results, although preliminary, identify short-term (i.e. one month) exposure to elevate levels of air pollutants as a possible risk factor for the development of acute isolated PE. Larger studies are needed to confirm our results.

Association between increased FVIIa-antithrombin complex/FVIIa ratio and pre-eclampsia.

OBJECTIVE: Activated factor VII-antithrombin (FVIIa-AT) complexes can be used to reflect the degree of intravascular exposure of tissue factor (TF). The aim of the present case-control study was to evaluate FVIIa-AT plasma levels during normal pregnancy and in pre-eclampsia (PE). METHODS: One hundred and five pregnant women were enrolled and namely n = 30 in the first (T1), n = 30 in the second (T2), n = 30 in the third (T3) trimester of pregnancy and n = 15 with PE. FVIIa-AT complexes were determined using a specific ELISA (Diagnostica Stago, Asnieres, France). RESULTS: FVIIa-AT complexes were significantly higher in pregnant (119 ± 24 pM) than in healthy (102 ± 12 pM, p = 0.001) women. No difference in FVIIa-AT levels between T3 women and with PE was observed. Interestingly, women with PE had significantly higher FVIIa-AT/FVIIa ratio than women during T3 (2.01 ± 0.44 versus 1.50 ± 0.29, p = 0.001). CONCLUSION: FVIIa-AT complexes plasma levels differed significantly between normal pregnancy and non-pregnant women. Moreover, FVIIa-AT/FVIIa ratio was higher in patients with PE than in normal pregnant women.

Thromboelastographic evaluation of coagulative profiles in pig-to-monkey kidney xenotransplantation.

BACKGROUND: Activation of the clotting cascade is central in acute xenograft rejection (AHXR) that occurs when pig organs are transplanted into primates. The coagulopathy reported in this model is a very complex process that involves simultaneously coagulation factors, platelets and phospholipid-bearing cells (i.e., leukocytes, red blood cells, and endothelial cells). Choosing whole blood for coagulation analysis theoretically appears more favorable compared with plasma. Whole blood rotation thromboelastometry (ROTEM(®) ) is a point-of-care global coagulation analyzer able to evaluate the characteristics of clot formation and lysis by dynamic monitoring. The aim of this study was to record thromboelastographic profiles, performed by ROTEM(®) , in a series of immunosuppressed nephrectomized primates that received a life-supporting kidney. METHODS: Of the eight primates, n = 4 received a pig kidney transgenic for human decay-accelerating factor (hDAF/Gal+); n = 2, an α 1,3-galactosyltransferase gene-knockout (GT-KO) pig kidney transgenic for human CD39, CD55, CD59 and fucosyltransferase (HTF); and n = 2, a GT-KO pig kidney transgenic for hDAF. Blood samples were collected before and at least once per week after transplantation till euthanasia. Intrinsic (INTEM) and extrinsic (EXTEM) coagulation pathways and the function of fibrinogen (FIBTEM) were evaluated. Thromboelastographic parameters considered were clotting time (CT, seconds) and clot formation time (CFT, seconds) in INTEM and EXTEM and maximum clot firmness (MCF, mm) in FIBTEM. The correlations between CT in INTEM and activated partial thromboplastin time (aPTT), CT in EXTEM and PT, CFT in INTEM and EXTEM, and platelet counts and MCF in FIBTEM and fibrinogen plasma levels were also considered. RESULTS: In all animals, thromboelastographic profiles showed progressive prolongation of CT (activation of coagulative cascade) in INTEM. A close correspondence was observed between (i) the prolongation of the CFT values (propagation of clot formation), both in INTEM and EXTEM, and the decrease in platelet counts; (ii) the reduction in MCF values (clot firmness) ​​in FIBTEM and the decrease in fibrinogen plasma levels. No concordance between CT in INTEM and aPTT and between CT in EXTEM and PT was observed. CONCLUSIONS: Our study demonstrated that ROTEM(®) analyzer could be a useful and complementary tool to study the consumptive coagulopathy, either "compensated" or "non-compensated," that takes place when transgenic pig kidneys are transplanted into primates. Larger and prospective studies are needed to confirm our results and to evaluate the role of ROTEM(®) to guide the management of consumptive coagulopathy in order to prolong the survival of the transplanted organ.

ABO blood groups and the risk of venous thrombosis in patients with inherited thrombophilia.

BACKGROUND: Although having a non-O blood type is now regarded as a risk factor for venous thromboembolism, the strength of this association is poorly defined, as is its interaction with inherited thrombophilia. MATERIALS AND METHODS: The prevalence of non-O blood group and inherited thrombophilia (deficiencies of natural anticoagulants, factor V Leiden and prothrombin G20210A mutation) was assessed in a series of 712 consecutive patients with proximal deep vein thrombosis of the lower limbs who were referred to our Institution between 2004 and 2010, and in 712 age- and gender-matched healthy volunteers. Odds ratios (OR) of deep vein thrombosis and their 95% confidence intervals (CI) were computed for non-O group and thrombophilia, both separately and in combination. RESULTS: A non-O blood group was present in 492 cases and 358 controls (OR 2.21; 95% CI, 1.78 to 2.75). A thrombophilic abnormality was present in 237 cases and 105 controls (OR 2.82; 2.18 to 3.66). The combination of non-O group and thrombophilia was present in 152 cases and 51 controls (OR 7.06; 4.85 to 10.28). DISCUSSION: Having a non-O blood group is associated with an increased risk of proximal deep vein thrombosis of the lower limbs with or without pulmonary embolism. The addition of inherited thrombophilia increases the thrombotic risk conferred by non-O group alone by almost 3-fold.

Circulating microparticles in carriers of factor V Leiden with and without a history of venous thrombosis.

Although factor V Leiden (FVL) is a major determinant of thrombotic risk, the reason why less than 10% of carriers eventually develop venous thromboembolic (VTE) events is unknown. Recent observations suggest that circulating levels of microparticles (MP) may contribute to the thrombogenic profile of FVL carriers. We measured the plasma level of annexin V-MP (AMP) platelet-MP (PMP), endothelial-MP (EMP), leukocyte-MP (LMP) and tissue factor-bearing MP (TF(+)MP), and the MP procoagulant activity (PPL) in 142 carriers of FVL (of these 30 homozygous and 49 with prior VTE), and in 142 age and gender-matched healthy individuals. The mean (± SD) level of AMP was 2,802 ± 853 MP/µl in carriers and 1,682 ± 897 in controls (p<0.0001). A statistically significant difference between homozygous and heterozygous carriers of FVL was seen in the level of PMP, EMP and LMP, but not in that of the remaining parameters. When the analysis was confined to carriers with and without a VTE history, the mean level of AMP was 3,110 ± 791 MP/µl in the former, and 2,615 ± 839 MP/µl in the latter (p<0.005). The mean level of all subtypes of circulating MP showed a similar pattern. The PPL clotting time was 39 ± 9 seconds (sec) in carriers, and 52 ± 15 sec in controls (p=0.003); and was 35 ± 8 sec in carriers with prior thrombosis, and 41 ± 10 sec in thrombosis-free carriers (p<0.005). Our study results suggest that circulating MP may contribute to the development of thrombosis in carriers of FVL mutation.