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Heparin-induced thrombocytopenia (HIT) occurs in 1-2% of patients with acute coronary events or cardiac surgery. Eekels and colleagues report that ticagrelor comedication must be taken into account by laboratory physicians for interpretation of functional tests for HIT, as the presence of the drug can cause false-negative results.

Essentials A pilot study for External Quality Assessment for testing of HIT is described. The qualitative accordance for the PF4/heparin IgG test was 97.6%. The qualitative accordance for functional HIT tests was considerably lower. External Quality Assessment for functional HIT tests is required. SUMMARY: Objective Heparin-induced thrombocytopenia (HIT) is a potentially life-threatening complication of heparin exposure. Diagnosis is most reliable using a combination of an enzyme immunoassay (EIA) that detects antibodies against platelet factor 4 (PF4)/heparin complexes ("antigen" assay) and a "functional" assay that detects platelet-activating properties of the pathogenic HIT antibodies. No External Quality Assessment (EQA) is available for a combination of the tests. Here we report on the results of the first international EQA. Methods The pilot EQA was organized by the Department of Transfusion Medicine, Universitätsmedizin Greifswald, Germany. Six serum samples of patients, which were referred to Greifswald for HIT diagnosis, and one negative control sample were distributed to seven participants in Germany, Canada, and Singapore. Participants were asked to report the optical density (OD) values of their local EIA test for IgG-specific antibodies against the PF4/heparin complexes and the results for a functional assay (HIPA or SRA). Consensus was defined as a minimum 70% agreement, i.e., agreement among at least five of the seven participating laboratories. Results and conclusion Six out of seven participants reported results for EIA, with a high quantitative accordance (97.6%). For the functional assay, consensus was reached for all samples except the negative control, for which some participants reported nonspecific reactivity. All HIT-negative samples were correctly diagnosed by all participants; for HIT-positive samples, consensus of 70% was reached. Although the limited availability of sample material is an obstacle to overcome, an EQA combining both EIA and functional testing is feasible.

Background Apoptotic pathways in platelets are important for their survival and function. Platelet apoptosis may be involved in the pathogenesis of immune thrombocytopenia (ITP), an autoimmune-mediated disease. In contrast to the intrinsic apoptosis pathway, not much is known about the extrinsic pathway mechanisms in platelets. Objectives To investigate the expression of proteins involved in the extrinsic apoptosis pathway, including the death receptors, adaptor and regulator proteins in human platelets. To determine a possible trigger of the extrinsic apoptosis pathway in platelets. Methods To investigate the expression of key markers of the extrinsic pathway we used targeted immunofluorescence and flow cytometry assays. To study their expression and interaction we performed Western blotting and co-immunoprecipitation. Treated platelets with different apoptosis triggers were subjected to flow cytometry. Results We could identify the protein expression of the pro-apoptotic proteins TRADD (Tumor Necrosis Factor Receptor type 1- Associated DEATH Domain protein), TRAF2/5, (TNF Associated Factor) and DEDAF (Death Effector Domain- Associated Factor), FADD (Fas-Associated protein with death domain) as well as the anti-apoptotic proteins DJ-1 (Deglycase 1) and c-FLIP in human platelets. ABT-737 treatment induced a disruption in the co-localization of DJ-1 with FADD. Platelets treated with ABT-737 showed an activation in caspase-3 and -8. The exposure to TNF (Tumor Necrosis Factor), FasL (Fas ligand), and TWEAK or to plasma derived from ITP patients, did not lead to changes in caspase-3 and -8 activation in platelets. Conclusions Human platelets express some proteins of the extrinsic apoptosis pathway which can be modulated only by ABT-737 treatment. However so far, no other apoptosis trigger or interaction with an external receptor have been yet identified.

Immune thrombocytopenia (ITP) is an autoimmune disease which leads to accelerated platelet clearance. We investigated the plasma cytokine, chemokine and growth factor signatures and their clinical significance in pediatric ITP patients during acute, chronic and follow-up stages as well as the effects of intravenous immunoglobulin (IVIg) treatment, by using the Multiplex technology. In acute ITP before and/or after IVIg treatment we found significantly increased plasma levels of the pro- (tumour necrosis factor-α (TNF-α), interleukin IL-15) and anti- (IL-1 receptor antagonist (Ra), IL-10 and the growth factor interferon γ-induced protein (IP-10)) inflammatory cytokines, compared to healthy controls. Except for IL1-Ra, these cytokines decreased to normal levels in chronic patients. In contrast, growth-regulated α protein (GRO) and soluble CD40 ligand (sCD40L), known as platelet-derived molecules, were found to be significantly decreased in acute and increased in chronic ITP patients compared to healthy controls. GRO levels positively correlated with the platelet counts in the follow-up and chronic cohort. Monocyte counts showed a significant positive correlation only with IP-10 levels in acute ITP after IVIg treatment and follow-up patients. Expression levels of mRNAs for macrophage inflammatory protein MIP1-β, IL-1Ra and GRO determined in peripheral blood mononuclear cells (PBMCs) were significantly reduced in both acute and chronic ITP compared to controls. Our findings suggest that the different clinical presentation of acute and chronic pediatric ITP and to a lesser extent the IVIg treatment effects are characterized overall by a counterbalanced cytokine, chemokine and growth factor pattern response that might exert a pathogenic role in this disease.

STAT3 mediates inflammation and modulates immunity. We found that in addition to its role in autoimmunity, over-activated STAT3 interferes in early erythro-myeloid precursor development and reduces commitment towards the erythroid lineage by interfering with the erythropoietin-STAT5 signalling pathway.

The molecular causes of many inherited platelet disorders are being unraveled. Next-generation sequencing facilitates diagnosis in 30% to 50% of patients. However, interpretation of genetic variants is challenging and requires careful evaluation in the context of a patient’s phenotype. Before detailed testing is initiated, the treating physician and patient should establish an understanding of why testing is being performed and discuss potential consequences, especially before testing for variants in genes associated with an increased risk for hematologic malignancies.

Inherited platelet disorders can affect "only platelets", occur as a "syndromic phenotype" or be associated with "increased risk of hematological malignancies". Genetic testing is attractive for diagnosis of inherited platelet disorders. However, many physicians who refer patient blood for genetic testing are unaware of the association of certain inherited platelet disorders with other risks. Inherited platelet disorders associated with minor-moderate bleeding rarely cause patient distress. In contrast, identification of a mutation associated with an increased risk of leukemia may cause a major psychological disease burden, without offsetting the beneficial impact on management. Guidelines recommend postponing genetic testing "until the patient reaches adulthood or at least until the child is mature enough to participate in decision making". In our opinion, outside research, (genetic) testing in children with inherited platelet disorders should only be performed if it influences management. In adults, genes causing inherited platelet disorders associated with an increased risk of hematological malignancies should only be tested after obtaining explicit informed consent.

A clinically asymptomatic 12-year-old girl showed microcytosis in routine examination. Cation exchange high performance liquid chromatography (HPLC), revealed two additional peaks eluting after Hb A and DNA sequencing uncovered a novel heterozygous mutation at codon 64 of the α1-globin gene. The hemoglobin (Hb) variant was annotated as Hb G-Waimanalo [A1]. Further analyses demonstrated a decreased oxygen affinity Hb compared to the normal Hb configuration.

Immune thrombocytopenia (ITP) is defined as an autoimmune disease that leads to platelet clearance by macrophages. It is well known that auto-reactive B cells and CD4+ T-helper (Th) cells, and in particular their cytokines, have been associated with ITP. Cytokines and chemokines are key players in our immune response to recruit different cells, e.g. macrophages and monocytes, to respond to certain inflammatory signals. Specific cytokines (i.e. TNF-a, IFN-g) are known to induce apoptosis in nucleated blood cells. To understand the role of cytokines and chemokines in acute ITP, we studied their plasma levels in 10 pediatric ITP patients at diagnosis with a median platelet count of 3 x 109/L (range < 1 to 22 x 109/L) and compared them with controls: healthy children (n=9; platelet count > 150 x 109/L); and chemotherapy-induced thrombocytopenia patients (cTP; n=9; median platelet count of 12 x 109/L; range: 3-53 x 109/L). ITP patients fulfilled the criteria for acute ITP and presented with mild to moderate bleeding symptoms. The median age at diagnosis was 3.4 yrs (range: 1.6 - 6.5 yrs); blood samples were taken prior to treatment. Luminex technology was used to measure plasma levels of 42 cytokines and chemokines. Markers of platelet apoptosis - activated caspase-3, -8 and -9 - and of platelet activation - CD62P and CD63 expression and PAC-1 binding - were measured by flow cytometry. Distinct plasma cytokine/chemokine patterns were observed in ITP patients compared with controls. Significantly increased levels of the Th1 cell commitment cytokines TNF-α (p < 0.01) and IFN-g (p < 0.05), as well as of the Th2 cytokines IL-6 (p < 0.01), IL-10 (p < 0.01) and IL-13 (p < 0.05), were identified in ITP patients. We have previously shown that there is activation of platelet caspase-3, -8 and -9 at diagnosis in acute paediatric ITP patients compared with controls (Winkler et al, Br J Haematol 2012;156:508). In ITP patients, but not in controls, a negative correlation between eotaxin and caspase- 3 (r2 = 0.72), -8 (r2 = 0.76) and -9 (r2 = 0.53) activity were observed, as well as a negative correlations between GM-CSF and caspase-8 (r2 = 0.52) and -9 (r2 = 0.33). Furthermore, we found a correlation between IL-13 and platelet activation as measured by CD62P (r2 = 0.87) and CD63 (r2 = 0.67) expression in ITP patients but not in controls. In summary, increased plasma levels of the cytokines TNF-α, IFN-g, IL-6, IL-10, and IL-13 were observed in ITP patients at initial presentation, suggesting that these cytokines contribute to the pathogenesis of the disease. Since IL-6 and IFN-g are known to activate macrophages, while higher levels TNF-α, IL-10 and IL-13 in the plasma are signs for activated T cells, our findings are consistent with the current model of ITP, in which activated macrophages induce B and T cells to produce anti-platelet autoantibodies. Our goal is to study the interplay between the immune system and the reduction of platelet count in ITP and to further define apoptosis/activation-related pathways in ITP platelets. Furthermore, we showed a correlation in ITP patients between the chemokine eotaxin and GM-CSF with caspase-3, -8 and -9 activity, and a correlation between IL-13 and platelet activation. Our results imply, that apoptosis and platelet activation at diagnosis in ITP play a role in the development of ITP, but the underlying mechanisms are still unknown and needs to be further evaluated by increasing the patient cohort in our study. Disclosures No relevant conflicts of interest to declare.

RNAi is a sequence-specific gene silencing mechanism induced by double-stranded RNA and a promising tool for the development of a durable gene therapy against HIV-1. Such RNAi attack usually focuses on targets within the HIV-1 RNA genome. Despite potent inhibition, we previously observed the rapid selection of RNAi-resistant HIV-1 variants with a mutated target sequence. A number of strategies were tested to prevent viral escape. Similar to the success of combination therapy with multiple anti-retroviral drugs, one can target HIV-1 with multiple short hairpin RNAs (shRNAs). Alternatively, one can design second-generation shRNAs to target favorite RNAi-resistance mutations in order to block specific viral escape routes. One could also combine RNAi with regular antiviral drug regimens. Another strategy involves the use of RNAi against cellular proteins that are involved in HIV-1 replication. The idea is that viral escape is more difficult in this setting. Many cellular co-factors have been described in literature, e.g. based on large RNAi-screens in cell lines. We have shown that long-term inhibition of HIV-1 replication is possible with RNAi against cellular co-factors. To identify relevant co-factors that are not essential for cellular function, primary cells are to be preferred over T cell lines. We propose that RNAi against both viral and cellular targets could be used as a new therapeutic approach in the combat against HIV-1 infection.