Granulocyte antibodies in male blood donors: can they trigger transfusion-related acute lung injury?

BACKGROUND: White blood cell-associated antibodies can lead to transfusion-related acute lung injury (TRALI). Female donors with a history of pregnancies have been identified as a main cause for these antibodies. Male or female donors without a history of pregnancy are considered as safe donors. STUDY DESIGN AND METHODS: Following the identification of two TRALI cases associated with blood products from male donors, we investigated the frequency of granulocyte-specific and human leukocyte antigen (HLA) antibodies in the entire blood donor population using a high throughput automated flow-cytometry-based granulocyte immunofluorescence test (Flow-GIFT). We investigated sera from 14,343 whole blood donors (female, n = 6974, 48.7%; male, n = 7369, 51.3%) using automated Flow-GIFT. Of the female blood donors, 60.4% had a history of pregnancy. Positive sera were retested by the standard granulocyte immunofluorescence test and granulocyte agglutination test. For the detection of HLA Class I and II immunoglobulin G antibodies, we used a commercial screening enzyme-linked immunosorbent assay. RESULTS: We detected in 924 (21.9%) of the 4212 females with a history of pregnancy antibodies against granulocyte antigens (n = 62, 1.5%), HLA Class I and/or II antigens (n = 864, 20.5%). Notably, in 3.5% (n = 96) of 2762 females without a history of pregnancy and in 2.1% (n = 154) of 7369 males antibodies against granulocyte antigens (n = 13, 0.47% and n = 45, 0.6%), HLA Class I and/or II (n = 83, 3% and n = 109, 1.4%, respectively), were also detected. CONCLUSION: Human neutrophil antigen antibodies are rare in male and females without a history of pregnancy compared to females with a history of pregnancy, but their relevance is not negligible.

Simvastatin and atorvastatin attenuate VCAM-1 and uPAR expression on human endothelial cells and platelet surface expression of CD40 ligand.

BACKGROUND: In addition to their cholesterol lowering ability, statins have proven pleiotropic effects in the cardiovascular system. Chronic inflammation with interactions between platelets and endothelial cells leads to an upregulation of activity markers of atherosclerosis. The purpose of this study was to investigate the effects of simvastatin and atorvastatin on platelets and endothelial cells in an in vitro endothelial cell model. METHODS AND RESULTS: After a 24 h incubation period with either simvastatin or atorvastatin (1 µmol/L), human umbilical vein endothelial cells were stimulated for 1 h with lipopolysaccharide (LPS), and were then incubated in direct contact with activated platelets. Platelet surface expression of CD40L and CD62P and expression of ICAM-1, VCAM-1, uPAR and MT1-MMP on endothelial cells were measured by flow cytometry. Supernatants were analyzed by ELISA for soluble MMP-1. The increased expression of VCAM-1 and uPAR on endothelial cells by stimulation with LPS and by direct contact with activated platelets was significantly reduced to a similar extent through pre-incubation with both atorvastatin and simvastatin (p < 0.05). Platelets without endothelial cell contact, but in direct contact with either statin, showed similar significant reductions in surface expression of CD40L (p < 0.005). CONCLUSIONS: These effects may explain the ability of statins to reduce the progression of atherosclerosis in addition to their cholesterol-lowering properties.

Platelet and monocyte activation in acute ischemic stroke--is there a correlation with stroke etiology?

An upregulation of platelet CD40 ligand (CD40L) and CD62P has been described in atherosclerotic cardiovascular diseases and among patients with acute cerebral ischemia. Correlation between platelet and monocyte activation and the etiology of ischemic stroke were examined in 41 patients with acute ischemic stroke. Compared to 10 controls, all patients with stroke showed a significantly elevated platelet expression of CD40L (P < .001) and had significantly higher amounts of platelet-monocyte aggregates (P = .002). Plasma levels of interleukin 7 were significantly lower in patients with stroke compared to controls (P = .006). Patients with small artery disease had a significantly higher platelet CD40L expression than patients with cardioembolic stroke (P = .029). Plasma levels of soluble CD40L were significantly higher in patients with large artery disease compared to patients with cardioembolic stroke (P = .047). In conclusion, patients with acute ischemic stroke show an upregulation of platelet CD40L and an activation of cellular coagulation with highest activation in the large artery disease subgroup.

Effects of nicotinic acid on endothelial cells and platelets.

BACKGROUND: Interactions between platelets and endothelial cells under inflammatory conditions lead to an increased expression of various activity markers of atherosclerosis in the vessel wall. The purpose of this study was to investigate possible protective effects of nicotinic acid in an in vitro endothelial cell model. METHODS: After a 24-hour incubation period with nicotinic acid (1 mmol/l), human umbilical vein endothelial cells were stimulated for 1 h with lipopolysaccharide and were then incubated in direct contact with activated platelets. Following this incubation, the expression of CD40L and CD62P on platelets and the expression of intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, uPAR, and MT1-MMP on endothelial cells were measured by flow cytometry. Supernatants were analyzed by ELISA for soluble MCP-1 and MMP-1. RESULTS: The increased expression of VCAM-1 on endothelial cells by proinflammatory stimulation with activated platelets was significantly reduced through preincubation with nicotinic acid (P<.05). Furthermore, platelets in direct contact with preincubated endothelial cells showed a significant reduction in their CD62P and CD40L expression when compared to platelets incubated with untreated endothelial cells (P<.05). Treatment with nicotinic acid did not have a significant effect on ICAM-1, uPAR, and MT1-MMP expression on endothelial cells. Levels of soluble MCP-1 and MMP-1 in supernatants were lower after preincubation with nicotinic acid. CONCLUSION: Nicotinic acid inhibits platelet activation after platelets contacted nicotinic acid treated endothelial cells and inhibits VCAM-1 expression on human endothelial cells under inflammatory conditions. These findings suggest a possible pleiotropic therapeutic relevance of nicotinic acid in atherosclerosis.

1α,25-dihydroxyvitamin D3 attenuates platelet activation and the expression of VCAM-1 and MT1-MMP in human endothelial cells.

OBJECTIVE: Inflammatory conditions contribute to increased expression of various activity markers in platelets and endothelial cells, leading to atherosclerotic changes in the vascular wall. The objective of this study was to investigate possible protective effects of 1α,25-dihydroxyvitamin D3 in an endothelial cell model. METHODS: After a 24-hour incubation with 1α,25-dihydroxyvitamin D3, human umbilical vein endothelial cells were stimulated with lipopolysaccharide (LPS) and incubated in direct contact with platelets. The expression of CD40L and CD62P in platelets, the expression of intercellular adhesion molecule-1, vascular cell adhesion molecule-1 (VCAM-1), the urokinase receptor uPAR and membrane type 1 matrix metalloproteinase (MT1-MMP) in endothelial cells and endothelial cell reactive oxygen species generation were measured by flow cytometry. Endothelial nitric oxide synthase was analyzed by Western blot. RESULTS: The increased expression of VCAM-1 and MT1-MMP in endothelial cells by proinflammatory stimulation with LPS and by direct contact with activated platelets was significantly reduced through preincubation with 1α,25-dihydroxyvitamin D3. Platelets in direct contact with preincubated endothelial cells showed significantly reduced CD62P expression when compared to platelets incubated with untreated endothelial cells. CONCLUSIONS: 1α,25-Dihydroxyvitamin D3 attenuates platelet activation and the expression of VCAM-1 and MT1-MMP in human endothelial cells and could have early therapeutic relevance in atherosclerotic diseases.

A novel tool for high-throughput screening of granulocyte-specific antibodies using the automated flow cytometric granulocyte immunofluorescence test (Flow-GIFT).

Transfusion-related acute lung injury (TRALI) is a severe complication related with blood transfusion. TRALI has usually been associated with antibodies against leukocytes. The flow cytometric granulocyte immunofluorescence test (Flow-GIFT) has been introduced for routine use when investigating patients and healthy blood donors. Here we describe a novel tool in the automation of the Flow-GIFT that enables a rapid screening of blood donations. We analyzed 440 sera from healthy female blood donors for the presence of granulocyte antibodies. As positive controls, 12 sera with known antibodies against anti-HNA-1a, -b, -2a; and -3a were additionally investigated. Whole-blood samples from HNA-typed donors were collected and the test cells isolated using cell sedimentation in a Ficoll density gradient. Subsequently, leukocytes were incubated with the respective serum and binding of antibodies was detected using FITC-conjugated antihuman antibody. 7-AAD was used to exclude dead cells. Pipetting steps were automated using the Biomek NXp Multichannel Automation Workstation. All samples were prepared in the 96-deep well plates and analyzed by flow cytometry. The standard granulocyte immunofluorescence test (GIFT) and granulocyte agglutination test (GAT) were also performed as reference methods. Sixteen sera were positive in the automated Flow-GIFT, while five of these sera were negative in the standard GIFT (anti-HNA 3a, n = 3; anti-HNA-1b, n = 1) and GAT (anti-HNA-2a, n = 1). The automated Flow-GIFT was able to detect all granulocyte antibodies, which could be only detected in GIFT in combination with GAT. In serial dilution tests, the automated Flow-GIFT detected the antibodies at higher dilutions than the reference methods GIFT and GAT. The Flow-GIFT proved to be feasible for automation. This novel high-throughput system allows an effective antigranulocyte antibody detection in a large donor population in order to prevent TRALI due to transfusion of blood products.

Rapid treatment of leukostasis in leukemic mantle cell lymphoma using therapeutic leukapheresis: a case report.

We describe a case of severe leukocytosis caused by leukemic mantle cell lymphoma (MCL), complicated by leukostasis with myocardial infarction in which leukapheresis was used in the initial management. A 73-year-old male presented to the emergency department because of fatigue and thoracic pain. Blood count revealed 630 × 10(9)/L WBC (white blood cells). The electrocardiogram showed ST-elevation with an increase of troponin and creatinine kinase. The diagnosis was ST-elevation myocardial infarction (STEMI) induced and complicated by leukostasis. Immunophenotyping, morphology, cytogenetic and fluorescence-in-situ-hybridization analysis revealed the diagnosis of a blastoid variant of MCL. To remove leukocytes rapidly, leukapheresis was performed in the intensive care unit. Based on the differential blood count with 95% blasts, which were assigned to the lymphocyte population by the automatic hematology analyzer, leukapheresis procedures were then performed with the mononuclear cell standard program on the Spectra cell separator. The patient was treated with daily leukapheresis for 3 days. The WBC count decreased to 174 × 10(9)/L after the third leukapheresis, with a 72% reduction. After the second apheresis, treatment with vincristine, cyclophosphamide, and prednisolone was started. The patient fully recovered in the further course of the treatment. To the best of our knowledge, this is the first report on blastoid MCL with leukostasis associated with a STEMI that was successfully treated by leukapheresis. Effective harvest of circulating lymphoma cells by leukapheresis requires adaptation of instrument settings based on the results of the differential blood count prior to apheresis.

Screening of human tumor antigens for CD4 T cell epitopes by combination of HLA-transgenic mice, recombinant adenovirus and antigen peptide libraries.

BACKGROUND: As tumor antigen-specific CD4+ T cells can mediate strong therapeutic anti-tumor responses in melanoma patients we set out to establish a comprehensive screening strategy for the identification of tumor-specific CD4+ T cell epitopes suitable for detection, isolation and expansion of tumor-reactive T cells from patients. METHODS AND FINDINGS: To scan the human melanoma differentiation antigens TRP-1 and TRP-2 for HLA-DRB1*0301-restricted CD4+ T cell epitopes we applied the following methodology: Splenocytes of HLA-DRB1*0301-transgenic mice immunized with recombinant adenovirus encoding TRP-1 (Ad5.TRP-1) or TRP-2 (Ad5.TRP-2) were tested for their T cell reactivity against combinatorial TRP-1- and TRP-2-specific peptide libraries. CD4+ T cell epitopes thus identified were validated in the human system by stimulation of peripheral blood mononuclear cells (PBMC) from healthy donors and melanoma patients. Using this strategy we observed that recombinant Ad5 induced strong CD4+ T cell responses against the heterologous tumor antigens. In Ad5.TRP-2-immunized mice CD4+ T cell reactivity was detected against the known HLA-DRB1*0301-restricted TRP-2(60-74) epitope and against the new epitope TRP-2(149-163). Importantly, human T cells specifically recognizing target cells loaded with the TRP-2(149-163)-containing library peptide or infected with Ad5.TRP-2 were obtained from healthy individuals, and short term in vitro stimulation of PBMC revealed the presence of epitope-reactive CD4+ T cells in melanoma patients. Similarly, immunization of mice with Ad5.TRP-1 induced CD4+ T cell responses against TRP-1-derived peptides that turned out to be recognized also by human T cells, resulting in the identification of TRP-1(284-298) as a new HLA-DRB1*0301-restricted CD4+ T cell epitope. CONCLUSIONS: Our screening approach identified new HLA-DRB1*0301-restricted CD4+ T cell epitopes derived from melanoma antigens. This strategy is generally applicable to target antigens of other tumor entities and to different HLA class II molecules even without prior characterization of their peptide binding motives.

Activation of platelets and cellular coagulation in cerebral small-vessel disease.

Platelets and monocytes play a pivotal role in the initiation and progression of large-vessel atherosclerosis. An up-regulation of various platelet and coagulation activation markers has been described in cardiovascular diseases and in patients with acute cerebral ischemia. In the present study the role of platelets and cellular coagulation activation in cerebral small-vessel disease (cSVD) was assessed. In 24 patients with cSVD but without established large-vessel disease, whole blood samples were obtained. Patients were divided into three subgroups (Fazekas 1, 2 and 3) according to extent of cSVD based on morphological magnetic resonance imaging criteria. Surface expression of CD40L and CD62P on platelets, tissue-factor exposition on monocytes and platelet-monocyte aggregates were measured with flow cytometry. Plasma levels of soluble CD40L, interleukin (IL)-6 and IL-7 were assessed by ELISA. Patients with cSVD show a significantly elevated expression of platelet CD40L (P < 0.001) and CD62P (P < 0.023), significantly elevated amounts of platelet-monocyte aggregates (P < 0.004), a significantly enhanced tissue-factor exposition on monocytes (P < 0.019) and significantly lower plasma levels of IL-7 compared to 10 healthy controls. However, this platelet and monocyte activation did not correlate with the severity of cSVD. Patients with cSVD show an up-regulation of the platelet CD40L and CD62P system and an activation of cellular coagulation which might contribute to the initiation and progression of cSVD.

The detection of platelet antibodies by simultaneous analysis of specific platelet antibodies and the monoclonal antibody-specific immobilization of platelet antigens: an interlaboratory comparison.

BACKGROUND: Glycoprotein (GP)-specific platelet (PLT) antibodies can cause allo- or autoimmune thrombocytopenia. Their detection is of high diagnostic value. The simultaneous analysis of specific PLT antibodies (SASPA) assay is based on simultaneous detection of various PLT-specific antibodies by flow cytometry and has entered routine use in our Mannheim institution. In this study, we performed an interlaboratory comparison investigation of PLT-specific antibodies using SASPA versus the "gold standard," the monoclonal antibody-specific immobilization of PLT antigen (MAIPA) assay. STUDY DESIGN AND METHODS: Sera from 194 patients with suspected PLT allo- or autoantibodies were tested against GPIIb/IIIa, IX, Ia/IIa, IV, and HLA Class I by SASPA (in Mannheim) and MAIPA (in Vienna). All data were reported blinded to those from the respective other method. Sensitivity studies included dilution studies with known antibodies against HPA-1a, -1b, -3b, -5b, and -15b and HLA Class I. RESULTS: Overall, results were concordant in 78.9%. The specificity and sensitivity of SASPA, based on the MAIPA results, were 97.3 and 86.3%, respectively, for the detection of alloantibodies. The respective results for the detection of autoantibodies were 95.3 and 44.9%. Serial dilution experiments with sera containing anti-HPA1a, -1b, -3b, -5b, and -15b and anti-HLA Class I revealed a higher sensitivity of the SASPA assay with all alloantibodies. CONCLUSION: In this first blind interlaboratory comparison, SASPA yielded similar results to those of MAIPA. The SASPA assay may be superior to the MAIPA assay for the detection of weak alloantibodies while simultaneous detection of a variety of antibody specificities or immunoglobulin classes and the need of fewer PLTs are obvious advantages.

Differential clinical significance of individual NKG2D ligands in melanoma: soluble ULBP2 as an indicator of poor prognosis superior to S100B.

PURPOSE: Cytotoxic lymphocytes interact with human tumor cells via the activating immunoreceptor NKG2D, recognizing a variety of stress-associated MIC and ULBP surface molecules. However, tumors can escape from this immunosurveillance by shedding NKG2D ligands (NKG2DL), rendering the soluble products detectable in patients' sera. EXPERIMENTAL DESIGN: To elucidate the clinical significance of NKG2DL diversity, we studied their expression on melanoma tissues and their presence as soluble molecules in sera from >200 melanoma patients and compared the latter with the well-established serum marker S100B. RESULTS: Immunohistochemistry revealed a heterogeneous expression of MIC and ULBP2 molecules between and within melanoma metastases. Compared with MIC, ULBP2 was less frequently expressed. Accordingly, elevated levels of soluble ULBP2 (sULBP2) were detected in sera of melanoma patients less frequently than elevated levels of soluble MICA (sMICA), although both soluble NKG2DL (sNKG2DL) were significantly increased compared with sera of healthy controls (P < 0.0001). Strikingly, elevated concentrations of sULBP2, but not of sMICA, were strongly associated with disease progression (P < 0.0001) and tumor load (P = 0.0003). Elevated serum levels of either sNKG2DL correlated with reduced overall survival, albeit considerably stronger for sULBP2 (P < 0.0001) than for sMICA (P = 0.011). In early-stage (I-III) melanoma patients, only sULBP2 (P < 0.0001) but neither sMICA nor S100B revealed prognostic significance. Multivariate analysis identified sULBP2 (P = 0.0015) and S100B (P = 0.013) but not sMICA as independent predictors of prognosis. CONCLUSION: Our data reveal marked differences in the clinical significance of individual sNKG2DL. Only sULBP2 is an independent predictor of prognosis, the significance of which is superior to the well-established and widely used melanoma serum marker S100B.

Rapid screening of granulocyte antibodies with a novel assay: flow cytometric granulocyte immunofluorescence test.

BACKGROUND: White blood cell (WBC)-associated antibodies can lead to severe pulmonary transfusion reactions (transfusion-related acute lung injury [TRALI]). Investigation of a large number of blood donor samples using the standard granulocyte immunofluorescence test (GIFT) and granulocyte agglutination test (GAT) proved to be difficult to perform due to the time-consuming process and the large quantity of test cells required. This study describes the novel flow cytometric GIFT (Flow-GIFT) method for a rapid detection of granulocyte antibodies by flow cytometric analysis. STUDY DESIGN AND METHODS: A total of 141 sera were analyzed for the presence of granulocyte antibodies that were previously associated with suspected TRALI. As test cells whole blood samples from human neutrophil antigen (HNA)-typed donors were isolated using cell sedimentation in a ficoll density gradient. WBCs were incubated with the respective serum and binding of antibodies to the test cells was detected using fluorescein isothiocyanate-conjugated anti-human antibody. Standard GIFT and GAT were performed as reference methods. RESULTS: Seven sera containing anti-HNA-3a, CD16, and HLA Class I were negative in the standard GIFT and eight sera containing anti-HNA-2a, anti-CD16, and anti-HLA Class I were not detected in the GAT. The novel Flow-GIFT was able to detect all granulocyte antibodies, which were only detectable in a combination of standard GIFT and GAT. In serial dilution tests, the Flow-GIFT detected the antibodies at higher dilutions than the reference methods GIFT and GAT. CONCLUSION: The Flow-GIFT method permits rapid detection of granulocyte antibodies requiring fewer donor test cells. This method is ideal for automation and will potentially open the way for screening of granulocyte antibodies in a large donor population.

Alimentary lipemia enhances procoagulatory effects of inflammation in patients with a history of acute myocardial infarction complicated by ventricular fibrillation.

INTRODUCTION: Acute myocardial infarction, often occurring postprandially, can be complicated by ventricular fibrillation. The role of acute alimentary lipemia and inflammation in the occurrence of ventricular arrhythmias in acute myocardial infarction has not been described yet. METHODS AND RESULTS: Before and 2 h after consumption of a defined fatty meal, blood samples of 27 patients with a history of acute myocardial infarction (AMI) were incubated with lipopolysaccharide (LPS). In 10 patients, AMI was complicated by ventricular fibrillation (VF), in 17 patients, AMI occurred without VF. CD40-ligand and CD62P expression on platelets, tissue-factor binding on monocytes and platelet-monocyte aggregates were measured with flow cytometry. Soluble CD40-ligand plasma levels were measured with an ELISA. With the meal, serum triglyceride levels increased from 211.85+/-94.60 mg/dl to 273.59+/-122.52 mg/dl (p=0.0002). LPS stimulation before the meal showed a non-significant tendency to increase platelet-monocyte aggregates and tissue factor on monocytes in both patient groups. LPS stimulation in acute alimentary lipemia significantly increased tissue-factor expression on monocytes in both patient groups and platelet-monocyte aggregates in patients with VF. Baseline plasma levels of soluble CD40L did not differ significantly between both groups. Acute alimentary lipemia significantly decreased total plasma levels of sCD40L, leading to a significantly lower level of sCD40L in patients with a history of VF. CONCLUSIONS: Alimentary lipemia enhances procoagulatory effects of inflammatory stimulation in patients with a history of AMI complicated by ventricular fibrillation. These observations might reveal a mechanism for an increased risk of VF in acute coronary syndromes in a postprandial state.

Endotoxin-induced effects on platelets and monocytes in an in vivo model of inflammation.

AIMS: Chronic inflammation is a major contributing factor to atherosclerosis and various markers of inflammation, fibrinolysis and coagulation are upregulated in patients with established atherosclerotic disease. The aim of this study was to investigate the direct and short-term effects of inflammation on platelet and monocyte activation with an in vivo model of endotoxemia in healthy volunteers. METHODS AND RESULTS: In this study, 13 healthy male subjects with a mean age of 29.5+/-5.4 years received intravenous administration of lipopolysaccharide (LPS; 20 IU/kg IV). The kinetics of CD40-ligand and CD62P expression on platelets, tissue-factor binding on monocytes and platelet-monocyte aggregates were measured by whole blood flow cytometry at baseline and at 1, 2, 4, 6 and 24 hours after LPS administration. Plasma levels of soluble CD40-ligand were measured with an ELISA over the same time course. Platelet-monocyte aggregates, tissue-factor binding on monocytes and surface expression of platelet CD40L significantly increased in experimental endotoxemia in vivo, reaching peak values 1 hour after LPS administration. All values returned to baseline after 24 hours. Surface expression of CD62P on platelets and plasma levels of sCD40L did not change significantly in response to LPS. CONCLUSIONS: In vivo administration of endotoxin leads to an activation of platelets and monocytes with an upregulation of proatherogenic CD40L on platelets. These findings underpin the role of inflammation in early atherogenesis through platelet and monocyte activation in an in vivo model.

Effects of alimentary lipemia and inflammation on platelet CD40-ligand.

INTRODUCTION: In patients with chronic hypercholesterolemia, the CD40-CD40L dyad is upregulated, contributing to the initiation and progression of atherosclerosis. Our aim was to describe the role of postprandial lipemia and inflammatory stimulation on platelet and monocyte activation and CD40-ligand (CD40L) levels. METHODS AND RESULTS: Before and 2 h after consumption of a defined fatty meal, whole blood samples of 31 healthy subjects were incubated with endotoxin (LPS). CD40-ligand and CD62P expression on platelets, tissue-factor expression on monocytes and platelet-monocyte aggregates were measured with flow cytometry. Soluble CD40-ligand plasma levels were measured with an ELISA. After the meal, serum triglyceride levels increased from 137.6+/-60.5 mg/dl to 201.5+/-75.0 mg/dl. Expression of CD40L and CD62P on platelets and plasma levels of soluble CD40L were significantly decreased. No significant changes after the meal were observed concerning tissue factor expression on monocytes and platelet-monocyte aggregates. Addition of LPS showed no significant effect concerning CD40L or CD62P expression on platelets, whereas the amount of platelet-monocyte aggregates significantly increased under LPS stimulation after the fatty meal. CONCLUSIONS: Acute alimenatry lipemia leads to a decreased expression of CD40L on platelets and a reduced plasma level of sCD40L, suggesting an increased turnover in the CD40L system. CONDENSED ABSTRACT: Before and after a fatty meal, blood samples of 31 healthy subjects were incubated with LPS. After the meal, expression of CD40L and CD62P on platelets and plasma levels of soluble CD40L were significantly decreased. Addition of LPS showed no effect concerning CD40L or CD62P expression, whereas the amount of platelet-monocyte aggregates significantly increased under LPS stimulation after the fatty meal.

Identification of HLA class I dependent immunogenic peptides from clonotypic TCRbeta expressed in cutaneous T-cell lymphoma.

The clonotypic T-cell receptor (TCR) is a potential target antigen for specific immunotherapy of cutaneous T-cell lymphoma (CTCL). We identified T-cell epitopes from the rearranged TCR beta chain of the malignant T-cell population by the "reverse immunology" approach. Peptide-specific T-cell lines were generated against predicted epitopes and tested for the recognition of tumor cells and cells transfected with the full-length DNA coding for TCRV beta chain. Two peptides derived from the clonotypic TCRVbeta of a HLA-A2 positive patient could induce peptide-specific T cells from peripheral blood mononuclear cells of healthy donors and the patient as assessed by IFN-gamma ELISpot assay. Furthermore, the reactive CTLs efficiently recognized autologous Sézary tumor cells, as well as HLA-A2 positive 293 cells transfected with recombinant plasmid expressing the corresponding TCRVbeta29 protein. Similar results were obtained in a HLA-A3+ patient for TCRVbeta7-Jbeta2.7. In conclusion, our experiments show that the TCR beta chain harbors epitopes suitable as targets for specific vaccination which might be a promising approach for the specific immunotherapy of cutaneous T-cell lymphoma patients.

Identification of a cross-reactive HLA-DRB1*0301-restricted CD4 T cell response directed against cholesterol-binding cytolysins from two different pathogens.

Cholesterol-binding cytolysins constitute an evolutionarily conserved family of pore-forming proteins expressed by different gram-positive pathogens. Listeriolysin O, one well-characterized member of the cytolysin family, is also known to induce specific CD4 and CD8 T cell responses upon infection of mice with Listeria monocytogenes. Here we describe an HLA-DRB1*0301-restricted listeriolysin O-derived T cell epitope that is conserved among several members of the cytolysin family. An HLA-DRB1*0301-restricted CD4+ T cell line, established from spleen lymphocytes of L. monocytogenes-infected HLA-DRB1*0301-transgenic mice, cross-reacted with a homologous peptide from perfringolysin O, a cytolysin expressed by Clostridium perfringens. Ex vivo analysis of infected mice revealed an even broader cross-reaction of T cells with homologous peptides derived from perfringolysin O, streptolysin O, and cereolysin O. Interestingly, a cross-reactive memory CD4+ T cell response against the homologous peptides derived from listeriolysin O and perfringolysin O could also be detected in the blood from healthy HLA-DRB1*0301+ human donors. Remarkably, this response was even present in donors who did not exhibit a memory T cell reactivity against a second, non-conserved HLA-DRB1*0301-restricted LLO-derived CD4 T cell epitope, suggesting that cytolysin-producing bacteria other than L. monocytogenes can stimulate a cross-reactive cytolysin-specific immunity.

Enhanced expression of platelet CD40-ligand by in vitro lipopolysaccharide-challenge in patients with ventricular fibrillation complicating acute myocardial infarction.

BACKGROUND: Acute myocardial infarction can be complicated by ventricular arrhythmias due to electrophysiological changes in the ischemic myocardium, but the exact predisposing factors causing ventricular fibrillation during myocardial infarction still remain unclear. A role of inflammatory stimulation on platelets as a potential risk factor for ventricular fibrillation during acute myocardial infarction has not been described yet. METHODS AND RESULTS: Whole blood samples of 21 patients with a history of acute myocardial infarction (AMI) and ventricular fibrillation (VF) were incubated with lipopolysaccharide (LPS). As a control group, we studied 19 patients without VF during AMI. CD40-ligand and CD62P expression on platelets and tissue factor binding on monocytes were measured by flow cytometry. Platelet-monocyte aggregates were measured by CD41 expression on platelets adherent to monocytes. Soluble CD40-ligand plasma levels were measured with an ELISA. Without LPS, no significant difference between the patient groups concerning CD40L expression on platelets was observed, but plasma levels of soluble CD40L were significantly higher in patients with a history of AMI with VF. After LPS stimulation, patients with a history of VF showed a significantly increased expression of CD40L in comparison to the patients without ventricular fibrillation, based on a significantly higher increase of CD40L expression. CD62P expression on platelets was significantly increased in patients with a history of VF. CONCLUSIONS: Patients with a history of VF complicating AMI show an enhanced expression of CD40L on platelets after in vitro lipopolysaccharide-challenge with an enhanced platelet activation.

Coagulation activation and expression of CD40 ligand on platelets upon in vitro lipopolysaccharide-challenge in patients with unstable angina.

BACKGROUND: Elevated markers of inflammation and coagulation are found in patients with coronary heart disease. A role of inflammatory stimulation on coagulation time and expression of CD40 ligand on platelets in acute coronary syndromes has not been described yet. METHODS AND RESULTS: Whole blood samples of 9 patients with coronary heart disease and stable angina, 10 patients with unstable angina, 7 patients with acute myocardial infarction and 7 patients without coronary heart disease were incubated with lipopolysaccharide (LPS). Coagulation time was measured in arterial and coronary blood with the ReoRox(R), a viscometric whole blood coagulometer. CD40L and CD62P expression on platelets and platelet-monocyte aggregates were measured by flow cytometry. Without LPS, patients with unstable angina showed a significantly decreased coagulation time in arterial and coronary blood compared to patients without coronary heart disease. After incubation with LPS, in patients with unstable angina, a significantly decreased coagulation time in coronary blood was observed compared to patients with stable angina or patients without coronary heart disease. CD40L expression on platelets in patients with unstable angina was significantly higher in arterial and coronary blood compared to patients with stable angina. No significant differences between the patient groups were observed concerning CD62P expression on platelets, tissue factor binding on monocytes, platelet-monocyte aggregates and plasma levels of platelet factor 4. CONCLUSIONS: Patients with unstable angina show an enhanced coagulation activation and an upregulation of CD40L on platelets. This may be of importance in the understanding of coronary plaque rupture and formation of coronary thrombosis.

Melanoma cell necrosis facilitates transfer of specific sets of antigens onto MHC class II molecules of dendritic cells.

Vaccine strategies that target dendritic cells (DC) in order to elicit immunity against tumors are the subject of intense research. For the induction and maintenance of anti-tumor immunity, CD4+ helper T cells are often required, which need to see appropriate MHC class II-peptide complexes on DC. So far, it remained widely unclear what type of tumor cells can feed the MHC class II processing pathway of DC with what type of antigens. Here, we report that peptide loading onto MHC class II molecules of myeloid DC is facilitated by melanoma cells undergoing necrotic rather than apoptotic cell death. Importantly, the set of MHC class II-associated peptides induced by necrotic tumor cells differed from those found upon engagement of apoptotic tumor cells. This may be due to the fact that only necrotic cells liberated heat shock proteins, which bind tumor-derived peptides and thereby may promote processing by DC. The potential of DC to activate T cells was kinetically controlled through their antigen receptivity: CD4+ T cells were easily stimulated upon encountering antigen early in DC maturation, whereas antigen capture at later maturation stages favored activation of CD8+ T cells. These findings may aid in designing future vaccination strategies and in identifying novel tumor-specific helper T cell antigens.