Tumor-derived exosomes are a source of shared tumor rejection antigens for CTL cross-priming.

The initiation of T-cell-mediated antitumor immune responses requires the uptake and processing of tumor antigens by dendritic cells and their presentation on MHC-I molecules. Here we show in a human in vitro model system that exosomes, a population of small membrane vesicles secreted by living tumor cells, contain and transfer tumor antigens to dendritic cells. After mouse tumor exosome uptake, dendritic cells induce potent CD8+ T-cell-dependent antitumor effects on syngeneic and allogeneic established mouse tumors. Therefore, exosomes represent a novel source of tumor-rejection antigens for T-cell cross priming, relevant for immunointerventions.

Fcgamma receptor-mediated induction of dendritic cell maturation and major histocompatibility complex class I-restricted antigen presentation after immune complex internalization.

Dendritic cells (DCs) express several receptors for the Fc portion of immunoglobulin (Ig)G (FcgammaR), which mediate internalization of antigen-IgG complexes (immune complexes, ICs) and promote efficient major histocompatibility complex (MHC) class II-restricted antigen presentation. We now show that FcgammaRs have two additional specific attributes in murine DCs: the induction of DC maturation and the promotion of efficient MHC class I-restricted presentation of peptides from exogenous, IgG-complexed antigens. Both FcgammaR functions require the FcgammaR-associated gamma chain. FcgammaR-mediated MHC class I-restricted antigen presentation is extremely sensitive and specific to immature DCs. It requires proteasomal degradation and is dependent on functional peptide transporter associated with antigen processing, TAP1-TAP2. By promoting DC maturation and presentation on both MHC class I and II molecules, ICs should efficiently sensitize DCs for priming of both CD4(+) helper and CD8(+) cytotoxic T lymphocytes in vivo.

Molecular characterization of dendritic cell-derived exosomes. Selective accumulation of the heat shock protein hsc73.

Exosomes are membrane vesicles secreted by hematopoietic cells upon fusion of late multivesicular endosomes with the plasma membrane. Dendritic cell (DC)-derived exosomes induce potent antitumor immune responses in mice, resulting in the regression of established tumors (Zitvogel, L., A. Regnault, A. Lozier, J. Wolfers, C. Flament, D. Tenza, P. Ricciardi-Castagnoli, G. Raposo, and S. Amigorena. 1998. Nat. Med. 4:594-600). To unravel the molecular basis of exosome-induced immune stimulation, we now analyze the regulation of their production during DC maturation and characterize extensively their protein composition by peptide mass mapping. Exosomes contain several cytosolic proteins (including annexin II, heat shock cognate protein hsc73, and heteromeric G protein Gi2alpha), as well as different integral or peripherally associated membrane proteins (major histocompatibility complex class II, Mac-1 integrin, CD9, milk fat globule-EGF-factor VIII [MFG-E8]). MFG-E8, the major exosomal component, binds integrins expressed by DCs and macrophages, suggesting that it may be involved in exosome targeting to these professional antigen-presenting cells. Another exosome component is hsc73, a cytosolic heat shock protein (hsp) also present in DC endocytic compartments. hsc73 was shown to induce antitumor immune responses in vivo, and therefore could be involved in the exosome's potent antitumor effects. Finally, exosome production is downregulated upon DC maturation, indicating that in vivo, exosomes are produced by immature DCs in peripheral tissues. Thus, DC-derived exosomes accumulate a defined subset of cellular proteins reflecting their endosomal biogenesis and accounting for their biological function.

The cell biology of antigen presentation in dendritic cells.

Dendritic cells are the most efficient antigen-presenting cells. They take up antigens and pathogens, generate MHC-peptide complexes, migrate from the sites of antigen acquisition to secondary lymphoid organs and, finally, they physically interact with and stimulate T lymphocytes. Indeed, dendritic cells are the only antigen-presenting cells that induce the activation of resting T cells, both in vitro and in vivo. Thus, dendritic cells initiate adaptive immune responses and determine tolerance. To do so, dendritic cells have developed unique membrane transport pathways. The molecular mechanisms responsible for the control of antigen uptake and processing, for the generation of MHC-peptide complexes and for their transport to the cell surface have been partially unraveled in the past two years.

Free-floating thrombi in the right heart: diagnosis, management, and prognostic indexes in 38 consecutive patients.

BACKGROUND: Floating right heart thrombi (FRHTS) are a rare phenomenon, encountered almost exclusively in patients with suspected or proven pulmonary embolism and diagnosed by transthoracic echocardiography. Their management remains controversial. METHODS AND RESULTS: We report on a series of 38 consecutive patients encountered over the past 12 years. Thirty-two patients were in NYHA class IV, 20 in cardiogenic shock. Echocardiography usually demonstrated signs of cor pulmonale: right ventricular overload (91.7% of the population), paradoxical interventricular septal motion (75%), and pulmonary hypertension (86. 1%). The thrombus was typically wormlike (36 of 38 patients). It extended from the left atrium through a patent foramen ovale in 4 patients. Pulmonary embolism was confirmed in all but 1. Mortality was high (17 of 38 patients) irrespective of the therapeutic option chosen: surgery (8 of 17), thrombolytics (2 of 9), heparin (5 of 8), or interventional percutaneous techniques (2 of 4). The in-hospital mortality rate was significantly linked with the occurrence of cardiac arrest. Conversely, the outcome after discharge was usually good, because 18 of 21 patients were still alive 47.2 months later (range, 1 to 70 months). CONCLUSIONS: Severe pulmonary embolism was the rule in our series of FRHTS (mortality rate, 44.7%). The choice of therapy had no effect on mortality. Emergency surgery is usually advocated. However, thrombolysis is a faster, readily available treatment and seems promising either as the only treatment or as a bridge to surgery. In patients with contraindications to surgery or lytic therapy, interventional techniques may be proposed.

Involvement of Livertine, a hepatocyte growth factor family member, in neural morphogenesis.

The formulation of the nervous system in vertebrate embryos involves extensive morphogenetic movements that include the folding of the neural tube and the migration of neural crest cells. Changes in cell shape and cell movements underlie neural morphogenesis but the molecular mechanisms involved in these processes in vivo are not well understood. Here, we show that a new member of the hepatocyte growth factor family, which we name Livertine, is expressed in frog embryos in neural cells including neural crest and midline neural plate cells which are undergoing pronounced morphogenetic movements. The ectopic expression of Livertine perturbs gastrulation and leads to positional changes in injected cells without apparently changing cell type. These results suggest that one of the normal functions of Livertine is the control of neural morphogenesis in the vertebrate embryo.

Early beneficial effect of streptokinase on left ventricular function in acute myocardial infarction.

The effect of intravenous streptokinase therapy on the time course of functional recovery was investigated in a controlled study of 64 patients randomized within 3 hours after the onset of acute myocardial infarction (AMI). Contrast ventriculography was performed 1 to 4 days after AMI and repeated 5 weeks later. Wall motion was analyzed by the centerline method in the central infarct, peripheral infarct and noninfarct regions. In patients with ventriculographic data at the early catheterization, streptokinase-treated patients had less severe hypokinesia in the central infarct region than control patients (-2.9 +/- 0.9 [n = 29] vs -3.4 +/- 0.7 standard deviations below normal [n = 21], p less than 0.05). The benefit of streptokinase was more marked in the peripheral infarct region (-1.5 +/- 0.7 vs -2.1 +/- 0.6, p less than 0.001). As a result, the ejection fraction was slightly higher in treated versus control groups (46 +/- 10 vs 43 +/- 7%, respectively; difference not significant). At 5 weeks, function in the streptokinase and control groups had diverged further because of continued improvement in the streptokinase-treated patients. This study shows that streptokinase benefits left ventricular (LV) function by 1 to 4 days after AMI, earlier than previously reported. The benefit was not limited to the peripheral infarct region, where ischemia might have been less severe, but was also seen in the central infarct region. The implication is that thrombolytic therapy can improve LV function during the period of myocardial stunning, while myocardial function is still recovering.

Predictive factors of effectiveness of streptokinase in deep venous thrombosis.

In a prospective study, 174 patients (118 women and 56 men, average age 44 years, range 14 to 82) with proximal extensive thrombosis received streptokinase (100,000 U/hour) for an average of 2.8 days (range 0.5 to 7) through the catheter of a temporary caval filter. Twenty-seven of 45 (60%) patients with nonocclusive clots were completely free of clots at the second phlebography versus 17 of 116 (14%) with occlusive clots (p less than 0.001). Among nonocclusive clots, proximal ones (caval, iliac and femoral) were more easily lysed than popliteal clots (88 of 116 [76%] vs 26 of 58 [45%]; p less than 0.001). In 41 of 132 (31%) patients, a daily injection of contrast medium through the filter-carrying catheter enabled the observation of a clot in the filter, which was lysed by streptokinase. Seventy patients with follow-up greater than 2 years (median 34 months) were examined clinically. Nineteen of 22 (86%) patients with venograms free of clots at discharge were free of clinical sequelae versus 16 of 48 (33%) without normal venograms (p less than 0.001). It is concluded that: (1) in the case of occlusive clots, only a few patients were normalized after streptokinase; (2) proximal nonocclusive clots were most effectively lysed; (3) when venograms were free of clots at discharge, the majority of patients did not have venous sequelae at follow-up; and (4) embolic migration seems to occur frequently with streptokinase.

Influence of interleukin-1 and tumor necrosis factor alpha on the growth of microglial cells in primary cultures of mouse cerebral cortex: involvement of colony-stimulating factor 1.

The influence of monokines and CNS-derived colony-stimulating factors (CSF) on the growth of microglia has been studied in mixed glial primary cultures stemming from mouse embryos. We observed that spontaneous growth of microglial cells in the presence of astrocytes is blocked by adding anti-colony-stimulating factor 1 (CSF-1) antibodies to the cultures. Both interleukin-1 (IL-1) and tumor necrosis factor-alpha(TNF alpha) strongly increased the number of microglial cells in mixed glial cultures and this effect was prevented by anti-CSF-1 antibodies. In contrast, anti-interleukin-3 (IL-3) or anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) antibodies did not significantly affect the in vitro growth of microglia. These results provide functional significance to astrocytic productions of CSF-1 and their modulations by IL-1 or TNF alpha.

Homozygous variant of antithrombin with lack of affinity for heparin: management of severe thrombotic complications associated with intrauterine fetal demise.

Patients with homozygous heparin-binding-site (HBS) qualitative antithrombin deficiencies are at significant risk of venous and arterial thrombosis. We report on the eighth case of homozygous HBS deficiency, and the fourth case concerning the Arg 47-Cys mutation. The proposita is a 25 year old, without known thrombotic antecedent, despite an oral contraceptive therapy for 7 years. After 25 weeks of a first pregnancy, she presented an intrauterine fetal demise complicated with deep vein thrombosis and pulmonary embolism. Heparin therapy was inefficient (no clinical nor angiographic improvement, no biological hypocoagulability). Heparin cofactor activity was < 10%, antigen concentration was normal. The crossed immunoelectrophoresis of patient's plasma, with and without heparin, showed a typical profile of qualitative HBS antithrombin deficiency. The molecular analysis revealed an homozygous Arg 4-Cys mutation. Antithrombotic therapy was achieved with continuous infusion of antithrombin concentrates (80 IU/kg/day) and unfractionated heparin (500 IU/kg/day) during 12 days, leading to clinical improvement, and followed by treatment with vitamin K antagonists. This observation emphasizes the risk of intrauterine fetal demise and the inefficiency of heparin therapy without antithrombin infusion in type II HBS homozygous deficiency. The management of a future pregnancy will probably require repeated infusions of antithrombin.

Effectiveness of intravenous streptokinase on infarct size and left ventricular function in acute myocardial infarction. Prospective and randomized study.

Within 3 h after the onset of symptoms of myocardial infarction, 64 patients were randomly assigned to receive either a 1-h intravenous infusion of 1,500,000 IU of streptokinase (SK) or a conventional therapy. Infarct size was estimated in CK gram equivalent (CKg) by measurement of CK-MB every 3 hours during a 48-h period. Enzymatic study revealed that myocardial infarction of the SK group was significantly smaller (61.4 +/- 45 vs. 89.4 +/- 56 CKg, p less than .05). Angiograms were performed at early stage and five weeks after myocardial infarction. At first coronary angiogram, the infarct-related vessel was open in 82% in the SK group versus 12% in controls. The SK group had higher global ejection fraction at second angiogram (57 +/- 11% vs. 49 +/- 11%, p less than .02), but differences in regional wall motion were not significant. By analysis according to patency or occlusion of infarct-related vessel, global and regional ejection fractions were significantly better at first and at second angiograms in all patients and in anterior infarctions with a patent infarct-related coronary artery. There was no significant difference for inferior infarction. We conclude that intravenous streptokinase infusion early after the onset of myocardial infarction reduces infarct size and improves left ventricular function, chiefly in anterior infarction. This benefit appears to be closely correlated to patency of infarct-related vessels.

[Enzyme histochemical study of tha atrioventricular junction area. Correlation with slow and fast atrial pathways]. / Etude histo-enzymologique de la région pré-tawarienne. Essai de corrélation avec les voies auriculaires lente et rapide.

It was traditionally admitted that junctional tachycardia was based on an intranodal reentry pathway. However, lesions created at a distance from the atrioventricular node by surgery or other physical means (fulguration or radiofrequency energy ablation) demonstrated that the reentry circuit could use the slow and fast atrial pathways. This study performed in 6 human hearts less than 1 hour after death was undertaken to perform enzyme histochemical analysis of the atrial pre-nodal region. The specimens were rapidly frozen in liquid nitrogen and sliced with a cryostat. After localisation of the different regions by routine staining methods, histochemical reactions were performed using the semi-permeable membrane method for weakly bound enzyme. Ten enzymes were studied covering the principal metabolic pathways. Though routine histological stain did not show any particular structures, the enzyme histochemical reactions showed a band of myocardium following the septal insertion of the tricuspid valve, joining the orifice of the coronary sinus to the posterior part of the compact atrioventricular node. This zone of myocardium had an enzymatic make-up similar to that of the sinus node. An analogous structure was also observed above the insertion of the anterior mitral leaflet. These two regions could constitute the trajectory of the slow conduction pathways.

[Congenital atrio-ventricular blocks in infants. Histological study of the conduction system]. / Les blocs auriculo-ventriculaires congénitaux du nourrisson. Etude histologique du système de conduction

The authors present a clinico-pathological study of three cases of complete congenital atrio-ventricular block in the infant. In one case the disorder was familial, and the heart was macroscopically normal. In the other two cases, the associated abnormalities (complete discontinuity of the aortic arch in one, and situs inversus with a patent ductus and high VSD in the other) were not responsible for the conductive defect. This was explained after study of serial sections of the inter-atrio-ventricular septum; these showed an interuption or absence of the penetrating portion of the bundle of His associated, in one case, with agenesis of the atrio-ventricular node.

[Atrio-ventricular block in rheumatoid polyarthritis. Histological study of the His-Tawara system. Apropos of 2 cases]. / Le bloc auriculo-ventriculaire de la polyarthrite rhumatoïde Etude histologiquie du systéme de His-Tawara. A propos de deux observations

A histological study of the conduction pathways was performed by serial sections in two patients who died with atrio-ventricular block in the course of rhumatoid arthritis. In the first case, the conduction disturbance was preceded by attacks of supra-ventricular paroxysmal tachycardia. The His-Tawara system was wholly infiltrated by a cast of lympho-plamocytes starting from rhumatoid nodules located at the base of both mitral and tricuspid valves and at the root of the aorta. The sinus node was the seat of a common fibrosis. In the second case, the atrio-ventricular block was secondary to amylosis which predominated in the central fibrous node and in the adjacent small coronary vessels. The His-Tawara system was completely destroyed down to its bifurcation. The sinus node was normal.

[Temporary caval filter allowing diagnosis and fibrinolytic therapy in patients suspect of massive pulmonary embolism]. / Filtre cave temporaire permettant le diagnostic et la fibrinolyse chez les patients suspects d'embolie pulmonaire massive.

The authors propose a therapeutic strategy enabling diagnosis, treatment and prevention in the same clinical procedure based on a series of 8 patients presenting with signs of massive pulmonary embolism (acute cardiorespiratory distress, shock, loss of consciousness, and/or cardiac arrest). A removable vena cava filter is rapidly introduced percutaneously via a brachial, femoral or jugular vein, and opened in the inferior vena cava. Using the same catheter and without a second venous puncture, pulmonary angiography and cavography are performed by digitised angiography using a small quantity of contrast medium (40 ml, 12 ml/sec). The diagnosis of massive pulmonary embolism (index of pulmonary obstruction 70 to 90%) was confirmed in 6 out of the 8 cases. In 2 patients, the contrast medium passed from the right atrium into the left atrium and one of the patients developed hemiplegia. Thrombolytic drugs (rt-PA followed by Streptokinase) were injected via the same filter catheter. The dosage of rt-PA was 20 to 50 mg as a bolus followed by 50 mg in 2 hours. Streptokinase was then infused at a dose of 100,000 U/hour for an average of 36 hours (24-48 hours), followed by intravenous heparin and oral vitamin K antagonists. Two patients required blood transfusion for haemorrhage during the relay with heparin. The temporary caval filter was removed in all cases but 3 patients required a definitive filter because of the persistence of life-threatening venous thrombosis. Seven of the 8 patients survived their pulmonary embolism. This approach is rapid, saves time, and spares the patients from more invasive procedures.

[Acute rheumatoid aortic insufficiency treated by valve replacement. Apropos of a case]. / Insuffisance aortique aiguë rhumatoïde traitée par un remplacement valvulaire. A propos d'un cas.

Rheumatoid valvular heart disease and aortic valve replacement for a rheumatoid lesion have been previously reported in the literature. The authors report the first case of emergency surgery for acute aortic regurgitation due to necrosis and rupture of a rheumatoid granuloma: the anatomopathological lesions observed were patholognomic.

[Intravenous thrombolysis by recombinant plasminogen activator (rt-PA) in unstable angina. A randomized multicenter study versus placebo]. / Thrombolyse intraveineuse par activateur tissulaire du plasminogène (rt-PA) dans l'angor instable. Etude multicentrique randomisée contre placebo.

Fifty patients (38 men) with unstable angina pectoris defined by: pain lasting > 15 minutes+percritical electrocardiographic changes+significant coronary narrowing on coronary angiography (Coro 1) performed within 24 hours, were treated in a double blind protocol with rt-PA (n = 25) 100 mg/90 minutes (10 mg bolus + 90 mg/90 minutes or placebo (n = 25). All received effective intravenous heparin and intravenous nitrates. Calcium antagonists and betablockers were prescribed in half the cases. Aspirin (100 mg orally per day) was prescribed after control coronary angiography (Coro 2) performed 24 +/- 6 hours after starting treatment. Qualitative and quantitative analysis (CAESAR system) was centralised. There were no differences in the angiographic findings between the two groups. Intracoronary thrombosis was observed in 43% (rt-PA) and 44% (placebo) in Coro 1 and in 17% and 28% in Coro 2. The incidence of myocardial revascularisation procedures was similar in the two groups: angioplasty: 12 (rt-PA) and 13 (placebo); coronary bypass surgery: 5 (rt-PA) and 6 (placebo). Seven patients developed myocardial infarction (5 rt-PA, 2 placebo), one of whom died of cardiogenic shock (placebo). Eighteen patients had haemorrhagic complications (14 rt-PA, 4 placebo; p < 0.002) mainly at the puncture sites (12/14, 3/4). Spontaneous haemorrhage occurred in 7/25 (28%) of patients on rt-PA (haematuria 3, gastrointestinal haemorrhage 2, haematuria + gastrointestinal haemorrhage 1, epistaxis 1) and in 1/25 patients on placebo (gastrointestinal haemorrhage) This study shows that intravenous thrombolysis with rt-PA in severe unstable angina pectoris doe not modify the clinical outcome or the angiographic lesions but exposes patients to a high risk of haemorrhagic complications.

[Primary aspergillus endocarditis]. / Endocardite aspergillaire primitive.

A 38-year old man was admitted for investigation of suspected endocarditis presenting with two cerebrovascular accidents and pyrexia. The initial clinical, echocardiographic and infectious investigations were normal, apart from a neutrophilic leukocytosis. The clinical course was marked by the recurrence of systemic embolism in the lower limbs, the appearance of cervical and axillary lymphadenopathy and, within a short period of time, of massive aortic valve vegetations. The diagnosis of aspergillosis was made from the culture of a peripheral embolus recovered by a Fogarty catheter and this was confirmed by the positivity of serological investigations. The patient died within two months despite antifungal therapy. Aspergillus endocarditis is characterised by its rapid progression, the volume and embolic tendency of the vegetations, the relative inefficacy of medical therapy and the potential benefits of early surgical management.

[Recording the electrogram of the sinus node. Effects of the injection of tetrodotoxin into the artery of the sinus]. / Enregistrement de l'électrogramme du noeud sinusal. Effets de l'injection de tétrodotoxine dans l'artère du sinus.

The cells of the SA node (SAN) are very resistant to the action of tetrodotoxine (TTX), a drug which. paradoxically, blocks depolarisation of the outer myocardial cells. Injection of TTX into the artery of the SAN brings about asystole; bur regular electrical activity, consisting of a slow wave of 200 to 300 ms duration, can still be picked up by an electrode placed on the SAN. This electrical activity, which can only be picked up over the SAN, and is resistant to TTX but blocked by acetylcholine, is interpretated as being the electrogram of the SAN. After the artery has been washed out by normal saline, the effect of TTX becomes progressively less; under these conditions, all degrees of sino-atrial block can be observed. Arising from a study of the phenomena of capture of the SA and AV nodes, of the effect of artrial stimulation, and of the time relationships between the various electrical events recorded, some hypotheses of the electrophysiology of the SAN and the sino-atrial conduction are put forward.

[Electrical activity in the region of the sino-atrial node. Experimental study]. / L'activité électrique de la région du noeud sinusal. Etude expérimentale

After finding the landmarks of the sino-atrial node in the dog by means of serial sections, the authors have recorded the electrical activity in the region of the sinus by means of bipolar and monopolar electrodes placed in contact with it. a)A preatrial wave has been recorded, and its origin is discussed. b) Mechanical destruction of the sino-atrial node is followed by the disappearance of this wave and the appearance of a slow junctional rhythm with a retrograde atriogram. c) When lignocain is applied directly to the sino-atrial node, the pre-atrial potential decreases and then disappears and the post-stimulation pause is prolonged. d) Clamping of the peri-sinus region gives rise to an incomplete block, followed by complete block, of the pre-atrial potential and the P wave. The post-stimulation pause remains normal. The disorders of rhythm which have followed these producedures may be regarded as constituting experimental models for sinus lesions and for sino-atrial block.