Lymphocyte Trapping Research Articles

Multitier mechanics control stromal adaptations in the swelling lymph node

Lymph nodes (LNs) comprise two main structural elements: fibroblastic reticular cells that form dedicated niches for immune cell interaction and capsular fibroblasts that build a shell around the organ. Immunological challenge causes LNs to increase more than tenfold in size within a few days. Here, we characterized the biomechanics of LN swelling on the cellular and organ scale. We identified lymphocyte trapping by influx and proliferation as drivers of an outward pressure force, causing fibroblastic reticular cells of the T-zone (TRCs) and their associated conduits to stretch. After an initial phase of relaxation, TRCs sensed the resulting strain through cell matrix adhesions, which coordinated local growth and remodeling of the stromal network. While the expanded TRC network readopted its typical configuration, a massive fibrotic reaction of the organ capsule set in and countered further organ expansion. Thus, different fibroblast populations mechanically control LN swelling in a multitier fashion.

A synergistic effect of Ambroxol and Beta-Glucosylceramide in alleviating immune-mediated hepatitis: A novel immunomodulatory non-immunosuppressive formulation for treatment of immune-mediated disorders

BackgroundAmbroxol hydrochloride is being used in respiratory diseases as a broncholytic therapy. Beta-Glucosylceramide (GC) is a naturally occurring glycosphingolipid that exerts an immune protective effect. The aim of the present study was to determine the synergistic immunomodulatory effect between these two compounds. MethodsImmune-mediated hepatitis was induced in the mice by administration of Con A. Mice were treated with either Ambroxol or GC alone or with the combination of both. Mice were followed for their effect on the liver injury, cytokine profile, and the immune system. ResultsCoadministration of Ambroxol and GC significantly alleviated the liver injury induced by ConA, as demonstrated by the decreased liver enzymes. The combined treatment had a statistically significant synergistic effect on the suppression of intrahepatic CD8+CD25+, an increase in the CD4/CD8 lymphocyte ratio and in the CD8+ intrahepatic lymphocyte trapping, as well as on change of serum in the IL4 levels. The beneficial effect was associated with the promotion of regulatory T lymphocytes subsets, and with a trend for a pro-inflammatory to an anti-inflammatory cytokine shift. ConclusionsCoadministration of Ambroxol with GC exerted a synergistic immunoprotective effect in a model of immune-mediated acute liver damage. Considering the high safety profile of both agents, the combination may become a novel immunomodulatory non-immunosuppressive therapeutic agent. Significance statementCoadministration of Ambroxol with glucocerebroside exerted a synergistic immunoprotective effect in a model of immune-mediated acute liver damage.

1480P M2 macrophages could promote an immunosuppressive phenotype in a prospective cohort of advanced gastric cancer patients

Tumor microenvironment plays a crucial role in cancer development and tumor-associated macrophages (TAMs) are emerging as key players. Nevertheless, TAMs role in advanced Gastric Cancer (GC) need to be further clarified. The inability of lymphocytes to reach tumor cells is an important mechanism of treatment resistance and cancer exclusion of CD8 T cells is correlated with a poor clinical outcome. Macrophages contribute to lymphocyte trapping by long-lasting interactions with CD8 T cells that causes immunosuppression and poor outcome.

Macrophages impede CD8 T cells from reaching tumor cells and limit the efficacy of anti–PD-1 treatment

In a large proportion of cancer patients, CD8 T cells are excluded from the vicinity of cancer cells. The inability of CD8 T cells to reach tumor cells is considered an important mechanism of resistance to cancer immunotherapy. We show that, in human lung squamous-cell carcinomas, exclusion of CD8 T cells from tumor islets is correlated with a poor clinical outcome and with a low lymphocyte motility, as assessed by dynamic imaging on fresh tumor slices. In the tumor stroma, macrophages mediate lymphocyte trapping by forming long-lasting interactions with CD8 T cells. Using a mouse tumor model with well-defined stromal and tumor cell areas, macrophages were depleted with PLX3397, an inhibitor of colony-stimulating factor-1 receptor (CSF-1R). Our results reveal that a CSF-1R blockade enhances CD8 T cell migration and infiltration into tumor islets. Although this treatment alone has minor effects on tumor growth, its combination with anti-PD-1 therapy further increases the accumulation of CD8 T cells in close contact with malignant cells and delays tumor progression. These data suggest that the reduction of macrophage-mediated T cell exclusion increases tumor surveillance by CD8 T cells and renders tumors more responsive to anti-PD-1 treatment.

S1P1 Modulator-Induced Gαi Signaling and β-Arrestin Recruitment Are Both Necessary to Induce Rapid and Efficient Reduction of Blood Lymphocyte Count In Vivo

S1P1 (sphingosine-1-phosphate receptor 1) agonists prevent lymphocyte egress from secondary lymphoid organs and cause a reduction in the number of circulating blood lymphocytes. We hypothesized that S1P1 receptor modulators with pathway-selective signaling properties could help to further elucidate the molecular mechanisms involved in lymphocyte trapping. A proprietary S1P1 receptor modulator library was screened for compounds with clear potency differences in β-arrestin recruitment and G protein alpha i subunit (G αi) protein-mediated signaling. We describe here the structure-activity relationships of highly potent S1P1 modulators with apparent pathway selectivity for β-arrestin recruitment. The most differentiated compound, D3-2, displayed a 180-fold higher potency in the β-arrestin recruitment assay (EC50 0.9 nM) compared with the G αi-activation assay (167 nM), whereas ponesimod, a S1P1 modulator that is currently in advanced clinical development in multiple sclerosis, was equipotent in both assays (EC50 1.5 and 1.1 nM, respectively). Using these novel compounds as pharmacological tools, we showed that although a high potency in β-arrestin recruitment is required to fully internalize S1P1 receptors, the potency in inducing G αi signaling determines the rate of receptor internalization in vitro. In contrast to ponesimod, the compound D3-2 did not reduce the number or circulating lymphocytes in rats despite high plasma exposures. Thus, for rapid and maximal S1P1 receptor internalization a high potency in both G αi signaling and β-arrestin recruitment is mandatory and this translates into efficient reduction of the number of circulating lymphocytes in vivo.

Bronchial epithelial injury in the context of alloimmunity promotes lymphocytic bronchiolitis through hyaluronan expression.

Epithelial injury is often detected in lung allografts, however, its relation to rejection pathogenesis is unknown. We hypothesized that sterile epithelial injury can lead to alloimmune activation in the lung. We performed adoptive transfer of mismatched splenocytes into recombinant activating gene 1 (Rag1)-deficient mice to induce an alloimmune status and then exposed these mice to naphthalene to induce sterile epithelial injury. We evaluated lungs for presence of alloimmune lung injury, endoplasmic reticulum (ER) stress, and hyaluronan expression, examined the effect of ER stress induction on hyaluronan expression and lymphocyte trapping by bronchial epithelia in vitro, and examined airways from patients with bronchiolitis obliterans syndrome and normal controls histologically. We found that Rag1-deficient mice that received mismatched splenocytes and naphthalene injection displayed bronchial epithelial ER stress, peribronchial hyaluronan expression, and lymphocytic bronchitis. Bronchial epithelial ER stress led to the expression of lymphocyte-trapping hyaluronan cables in vitro. Blockade of hyaluronan binding ameliorated naphthalene-induced lymphocytic bronchitis. ER stress was present histologically in >40% of bronchial epithelia of BOS patients and associated with subepithelial hyaluronan deposition. We conclude that sterile bronchial epithelial injury in the context of alloimmunity can lead to sustained ER stress and promote allograft rejection through hyaluronan expression.

Trapping of naive lymphocytes triggers rapid growth and remodeling of the fibroblast network in reactive murine lymph nodes

Adaptive immunity is initiated in T-cell zones of secondary lymphoid organs. These zones are organized in a rigid 3D network of fibroblastic reticular cells (FRCs) that are a rich cytokine source. In response to lymph-borne antigens, draining lymph nodes (LNs) expand several folds in size, but the fate and role of the FRC network during immune response is not fully understood. Here we show that T-cell responses are accompanied by the rapid activation and growth of FRCs, leading to an expanded but similarly organized network of T-zone FRCs that maintains its vital function for lymphocyte trafficking and survival. In addition, new FRC-rich environments were observed in the expanded medullary cords. FRCs are activated within hours after the onset of inflammation in the periphery. Surprisingly, FRC expansion depends mainly on trapping of naïve lymphocytes that is induced by both migratory and resident dendritic cells. Inflammatory signals are not required as homeostatic T-cell proliferation was sufficient to trigger FRC expansion. Activated lymphocytes are also dispensable for this process, but can enhance the later growth phase. Thus, this study documents the surprising plasticity as well as the complex regulation of FRC networks allowing the rapid LN hyperplasia that is critical for mounting efficient adaptive immunity.

Using Magnetic Resonance Imaging to Evaluate Dendritic Cell-Based Vaccination

Cancer immunotherapy with antigen-loaded dendritic cell-based vaccines can induce clinical responses in some patients, but further optimization is required to unlock the full potential of this strategy in the clinic. Optimization is dependent on being able to monitor the cellular events that take place once the dendritic cells have been injected in vivo, and to establish whether antigen-specific immune responses to the tumour have been induced. Here we describe the use of magnetic resonance imaging (MRI) as a simple, non-invasive approach to evaluate vaccine success. By loading the dendritic cells with highly magnetic iron nanoparticles it is possible to assess whether the injected cells drain to the lymph nodes. It is also possible to establish whether an antigen-specific response is initiated by assessing migration of successive rounds of antigen-loaded dendritic cells; in the face of a successfully primed cytotoxic response, the bulk of antigen-loaded cells are eradicated on-route to the node, whereas cells without antigen can reach the node unchecked. It is also possible to verify the induction of a vaccine-induced response by simply monitoring increases in draining lymph node size as a consequence of vaccine-induced lymphocyte trapping, which is an antigen-specific response that becomes more pronounced with repeated vaccination. Overall, these MRI techniques can provide useful early feedback on vaccination strategies, and could also be used in decision making to select responders from non-responders early in therapy.

β-Glycoglycosphingolipid-Induced Alterations of the STAT Signaling Pathways Are Dependent on CD1d and the Lipid Raft Protein Flotillin-2

Beta-glucosylceramide has been shown to affect natural killer T cell function in models of inflammation. We, therefore, investigated the effects of different beta-glycosphingolipids, including beta-glucosylceramide, on STAT (signal transducers and activators of transcription) signaling pathways and determined whether these effects were mediated by lipid raft microdomains and/or CD1d molecules. The effects of alpha- and beta-structured ligands on the lipid raft protein flotillin-2 were studied in both natural killer T hybridoma cells and leptin-deficient mice. To determine whether CD1d was involved in the effects of the beta-glycosphingolipids, an anti-CD1d blocking antibody was used in a cell proliferation assay system. The downstream effects on the protein phosphorylation levels of STAT1, STAT3, and STAT6 were examined in both immune-mediated hepatitis and hepatoma models. The effects of beta-glycosphingolipids on the STAT signaling pathways were found to be dependent on CD1d. Lipid rafts were affected by both the dose and ratio of the beta-glycosphingolipids and the acyl chain length, and these effects were followed by downstream effects on STAT proteins. Our results show that beta-glycosphingolipids have beneficial effects in natural killer T cell-dependent immune-mediated metabolic and malignant animal models in vivo.

Blockade of leucocyte function-associated antigen-1 (LFA-1) decreases lymphocyte trapping in the normal pulmonary vasculature: studies in the isolated buffer-perfused rat lung.

Adhesion molecules regulate the migration of lymphocytes in lymphoid and non-lymphoid organs. In the lung, little is known about lymphocyte sticking and migration through the pulmonary vascular endothelium in physiological or pathological situations. Therefore the isolated buffer-perfused rat lung was used to investigate the mobilization of lymphocytes out of the normal lung into the venous effluent and to the bronchoalveolar space. The lymphocyte subset composition was characterized in the venous effluent, the lung tissue and the bronchoalveolar lavage (BAL) using immunocytology. Lymphocytes continuously left the normal lung at a total of 5.0 +/- 0.7 x 106 cells within the first hour of perfusion. The injection of 200 x 106 lymphocytes via the pulmonary trunk increased the venous release of lymphocytes by 170%. To investigate the effect of LFA-1 and CD44 on the adhesion of lymphocytes to the pulmonary endothelium, lymphocytes preincubated with an anti-LFA-1 MoAb, which blocks the interaction of LFA-1 and intercellular adhesion molecule-1 (ICAM-1), or lymphocytes preincubated with an anti-CD44 MoAb, were injected. The injection of LFA-1-blocked lymphocytes led to an increase by 70% of injected cells recovered in the perfusate within the first hour, whereas anti-CD44 treatment of injected lymphocytes had no effect. The LFA-1-blocked lymphocytes showed higher numbers of T and B cells in the effluent. Thus, the present experiments demonstrate that LFA-1 influences the trapping of lymphocytes in the vasculature of the healthy rat lung.

β-Glycosphingolipids-mediated lipid raft alteration is associated with redistribution of NKT cells and increased intrahepatic CD8+ T lymphocyte trapping

The aim of this study was to determine the effect of beta-glycosphingolipids on intra-hepatic natural killer T (NKT) lymphocyte regulatory function and on lymphocyte trapping via alteration of cell membrane lipid rafts. Immune-mediated colitis was induced by intracolonic instillation of trinitrobenzene sulfonic acid. Mice were treated with beta-lactosylceramide (LC), beta-glucosylceramide (GC), beta-galactosylceramide, ceramide, or a combination of both GC and LC (IGL), or solvent alone. Lipid rafts were investigated by fluorescence-activated cell sorting analysis of ganglioside-GM1 and fluorescence microscopy of structure. Administration of beta-glycosphingolipids resulted in an increased intrahepatic/peripheral NKT ratio, increased intrahepatic CD8+ lymphocyte trapping, decreased serum interferon-gamma (IFN-gamma) levels and decreased serum IFN-gamma/interleukin-10 ratio. Administration of GC, LC, or IGL significantly altered the levels of GM1, a key marker of lipid rafts, on NKT regulatory lymphocytes. The immune modulatory effect of beta-glycosphingolipids was associated with increased survival and significant alleviation of colitis as determined by improvement in both the macroscopic and microscopic scores. In conclusion, administration of beta-glycosphingolipids increased NKT regulatory lymphocyte redistribution and intrahepatic CD8(+) T lymphocyte trapping, resulting in alleviation of immune-mediated colitis. The effects of these naturally occurring compounds were associated with modification of the T lymphocyte lipid raft structure, which is a site for immune modulation.

Modulation of intracellular machinery by β-glycolipids is associated with alteration of NKT lipid rafts and amelioration of concanavalin-induced hepatitis

The integrity of lipid rafts in cell membranes is important for signal transduction. Aim To determine the distinct effects of β-glycolipids on the composition of lipid rafts in natural killer T (NKT) cells and on the level of expression of flotillin-2, leukocyte-specific protein tyrosine kinase (Lck), and STAT1-associated pathways. Methods The effects of glycolipids were determined by composition analysis of the raft domains, FACS analysis of the distribution patterns for the raft ganglioside, GM1, and fluorescence microscopy of raft patching. To evaluate the effects of the immune environment on glycolipid-associated alteration of lipid rafts, hepatitis was induced by an intravenous injection of concanavalin A (ConA) in mice treated with various glycolipids. Results The administration of β-glucosylceramide, β-lactosylceramide, and a combination of both significantly altered GM1 content in lymphocyte membranes in an environment-dependent manner. These effects were associated with altered expression levels of flotillin-2, Lck, and STAT1, and with a significant decrease in intrahepatic CD8 + lymphocyte trapping and the alleviation of ConA-induced hepatitis. The administration of α-glycolipids failed to induce similar effects. Conclusions The alteration in the expression levels of flotillin-2, Lck, and STAT1 that occurs concomitantly with changes in lipid raft composition and structure following the administration of β-glycolipids in ConA-induced hepatitis is microenvironment-dependent and is associated with decreased intrahepatic CD8 + T lymphocyte trapping and amelioration of immune-mediated hepatitis.

Administration of β-glycolipids overcomes an unfavorable nutritional dependent host milieu: a role for a soy-free diet and natural ligands in intrahepatic CD8+ lymphocyte trapping and NKT cell redistribution

Soy-based diets are a major source of sphingolipids and play a complicated role in various aspects of the immune system. Administration of β-glycolipids, including β-glucosylceramide (GC), β-lactosylceramide (LC) and a 1:1 combination of GC and LC (IGL) were shown to exert immune-modulatory effects. Aim To examine the effects of a soy-free diet, and several β-glycolipids on concanavalin A (ConA)-induced hepatitis in the presence of an altered host glycolipid milieu. Methods ConA hepatitis was induced in C57BL/6 mice that were fed a soy-free diet (glycolipid content 200 μmol/kg). Two hours prior to administration of ConA, animals were injected IP with GC, LC, IGL or PBS. Animals were sacrificed 6 h after ConA administration. Results Both a soy-free diet and administration of β-glycolipids were associated with significant alterations in the distribution of NKT cells. Specifically, there was a decrease in intrahepatic and an increase in intrasplenic NKT lymphocytes. β-glycolipids prevented the ConA-induced intrahepatic CD8 lymphocyte trapping, not seen in mice with only a soy-free diet. Both a soy-free diet and β-glycolipids alleviated ConA-induced hepatitis by inhibiting IL10 secretion and increasing IL12 serum levels. The effect of IGL was clinically and immunological superior to that of either glycolipid alone. Conclusions Both a soy-free diet and β-glycolipids can overcome the unfavorable host milieu in the setting of ConA hepatitis. The host glycolipid milieu profoundly influenced the immune and clinical effects of various insults, and suggests that alteration of the glycolipid background of the host can serve as a novel therapeutic tool.

Intrahepatic CD8+ lymphocyte trapping during tolerance induction using mushroom derived formulations: A possible role for liver in tolerance induction

To determine the immunomodulatory effect of Shiitake (a mushroom extract), we tested its effect on liver-mediated immune regulation in a model of immune-mediated colitis. Four groups of mice were studied. Colitis was induced by intracolonic instillation of TNBS in groups A and B. Groups A and C were treated daily with Shiitake extract, while groups B and D received bovine serum albumin. Mice were evaluated for development of macroscopic and microscopic. The immune effects of Shiitake were determined by FACS analysis of intra-hepatic and intrasplenic lymphocytes and IFN-gamma ELISPOT assay. Administration of Shiitake resulted in marked alleviation of colitis, manifested by significant improvement in the macroscopic and microscopic scores, and by reduction in IFN-gamma-producing colonies in group A, compared to group B mice (1.5 pfu/mL vs 3.7 pfu/mL, respectively). This beneficial effect was associated with a significant increase in the intra-hepatic CD8(+) lymphocyte trapping, demonstrated by an increased intrasplenic/intrahepatic CD4/CD8 lymphocyte ratio. These effects were accompanied by a 17% increase in the number of intrahepatic natural killer T (NKT) cells. A similar effect was observed when Shiitake was administered to animals without disease induction. Shiitake extract affected liver-mediated immune regulation by altering the NKT lymphocyte distribution and increasing intrahepatic CD8(+) T lymphocyte trapping, thereby leading to alleviation of immune-mediated colitis.

Alleviation of Acute and Chronic Graft-Versus-Host Disease in a Murine Model Is Associated with Glucocerebroside-Enhanced Natural Killer T Lymphocyte Plasticity

Natural killer T (NKT) lymphocytes play a role in graft-versus-host disease GVHD (GVHD). Glucocerebroside (GC) is a naturally occurring glycolipid that plays a role in the immune modulation of NKT lymphocytes. This study aims to determine the effect of GC in murine models of semiallogeneic/acute and chronic GVHD. Acute and chronic GVHD were generated by fusion of splenocytes from C57BL/6 to (C57BL/6xBalb/c) F1 mice, and from B10.D2 donor mice into Balb/c, respectively. Recipients were treated daily with GC. Histological and immunological parameters of GVHD were assessed. Treatment with GC significantly alleviated GVHD in both models The beneficial effect of GC was associated with an increase in the intrahepatic/peripheral NKT lymphocyte ratio in the semiallogeneic/acute model. This ratio was decreased in the chronic GVHD model. A significant increase in intrahepatic CD8+ lymphocyte trapping was noted in the semiallogeneic/acute model, whereas the opposite effect was observed in the chronic GVHD model. Administration of GC led to decreased serum interferon-gamma and increased serum interleukin-4 levels in the Th1-mediated model, whereas the opposite effect was observed in the Th2-mediated models. GC ameliorates GVHD in both Th1- and Th2-mediated murine models, suggesting it is able to differentially affect the immune system. GC may alleviate immunologically incongruous disorders, and may be associated with "fine tuning" of immune responses.

Orientation diagnostique devant une lymphopénie

Points essentielsUne lymphopénie est définie par un nombre de lymphocytes circulants < 1 500/mm3 chez l’adulte et 4 500/mm3 chez l’enfant avant 8 mois.Nous proposons de classer les lymphopénies en fonction de leur mécanisme supposé•les insuffisances de production, qui regroupent les déficits immunitaires primitifs ou secondaires à une dénutrition et/ou une carence en zinc•les excès de catabolisme comprenant la radiothérapie, la chimiothérapie, les traitements immunosuppresseurs, l’infection VIH et le lupus érythémateux systémique•les modifications de la répartition des lymphocytes, qui comprennent principalement l’hypersplénisme, certaines infections virales, le choc septique, les brûlures étendues, les granulomatoses et la corticothérapie•les autres causes de lymphopénie, dont le mécanisme est encore mal compris : ethnie (Éthiopiens), insuffisance rénale, lymphome, tumeur solide, lymphopénie CD4 idiopathique.

Systemic Viral Infections and Collateral Damage in the Liver

The liver is involved in infections by hepatotropic viruses that replicate in the liver and for which the liver is the main target. These include hepatitis A, hepatitis B, hepatitis C, and hepatitis E viruses. In all of these infections, hepatitis and liver damage arise as a consequence of the immune response to virus within the liver.1 In addition, the liver can be affected as part of a generalized host infection with viruses that primarily target other tissues, particularly the upper respiratory tract. Examples of this phenomenon include the herpes viruses (Epstein-Barr virus, cytomegalovirus [CMV], and herpes simplex virus), parvovirus, adenovirus,2 and severe acute respiratory syndrome (SARS)-associated coronavirus.3 Liver involvement in nonhepatotropic viral infections can range from mildly deranged liver biochemistry to fulminant liver failure. In most of these infections, hepatitis is thought to be a consequence of an immune response to viral antigens with a close topographic association between the presence of viral antigens and the associated inflammatory infiltrates in the liver. Loss of immune control may be responsible for the development of hepatitis in CMV hepatitis4 and other opportunistic viral infections such as adenovirus.4 Similar activities may also be involved in SARS-associated hepatitis, which is characterized by focal lobular lymphocytic infiltrates.5 The paper by Polakos et al6 in this issue of The American Journal of Pathology broadens the mechanism by which viruses can cause hepatitis by demonstrating that viral-specific CD8+ T cells, generated in response to a viral infection restricted to sites outside the liver, can trigger T-cell-mediated hepatitis in the absence of viral antigens in the liver. They describe the involvement of the liver during pulmonary infection with influenza virus and demonstrate that hepatitis can occur even in the absence of detectable virus in the liver. The authors describe the hepatitis in influenza infection as “collateral damage” and suggest that it occurs as a consequence of the recruitment to the liver of CD8+ effector T cells that expand systemically in response to the viral infection. These observations are of great importance for understanding the involvement of the liver in systemic infections and elucidate some of the clinical syndromes of liver inflammation that cannot be easily explained by invoking antigen-specific T-cell responses in the liver.

Trapping and Collection of Lymphocytes Using Microspot Array Chip and Magnetic Beads

A microspot array chip, which has microspots of a magnetic thin film patterned on a glass substrate, was fabricated for trapping individual cells and for measuring their cellular response. The chip was easily fabricated by conventional semiconductor fabrication techniques on a mass production level as a disposable medical device. When a solution of lymphocyte-bound-magnetic beads was poured into the magnetized chip, each lymphocyte was trapped on each microspot of the magnetic thin film. The trapped cells were easily recovered from the chip using a micromanipulator. The micro-spot array chip can be utilized for arraying live cells and for measuring the response of each cell. The chip will be useful for preparing on array of different kinds of cells and for analyzing cellular response at the single cell level. The chip will be particularly useful for detecting antigen-specific B-lymphocytes and antigen-specific antibody complementary deoxyribonucleic acid (cDNA).

The role of Epstein–Barr virus in acute and chronic hepatitis

Epstein-Barr virus has a seroprevalence of more than 80% world wide and is known to be associated with hepatitis. However, little is known about the underlying pathogenesis and immunmechanisms and no standard diagnostic criteria to diagnose EBV-hepatitis are available. We collected liver biopsies (n=21) with the tentative diagnosis of EBV induced hepatitis according to pathological changes and traceable EBV genome by PCR. Correlation with serological data revealed acute in seven cases, convalescent in two cases, past EBV infection in six cases. Viral RNA was visualised by in situ hybridisation within nuclei of lymphocytes. In seven of 68 liver biopsies with the diagnosis 'liver disease of unknown aetiology' EBV genome in the tissue was demonstrated indicating a possible role for EBV in the induction of hepatitis or a trapping of infected lymphocytes within the liver. In a control group of 20 EBV-seropositive patients with steatohepatitis EBV-DNA PCR of the liver tissue was negative. Immunohistochemistry identified CD3 and CD8 positive T-lymphocytes as the main lymphocytic infiltrate in EBV hepatitis. EBV hepatitis should be taken into consideration in case of typical histopathological changes and a positive DNA PCR of liver biopsy. Serological confirmation of the diagnosis is inevitable.

Leishmaniasis in Canis familiaris – a Report About Microvascular and Cellular Architecture of the Infected Spleen

Leishmaniases are a globally widespread group of parasitic diseases from the group of anthropozoonoses. They are caused by an intracellular protozoan parasite that causes a wide spectrum of diseases in humans and dogs worldwide. In fact, the dog is considered one of the most important reservoir. The spleen is one of the several haematopoietic and immunocompetent organs involved. As this organ is a blood filter, the authors looked for the expression of this infection over the microvascular environment and modifications of the spleen cell population related to immunological responses to this parasitic condition.Tools: Scanning electronic microscopy over intact tissue and corrosion casts, transmission electronic microscopy, histology and immunohistochemistry (MAC 387 and CD3).Results: Our results show three important modifications concerning the microvascular architecture of the spleen when compared to the normal pattern. A striking scarcity of the sinusoidal system sheath that surrounds the central arteries of the white pulp, a huge development of pulp venules and veins, differentiation of typical features of high endothelial venular cells.Remarks: According to our results it seems that independent of the virulence of the parasite involved and the kind of immunity prevalent in a particular host, the spleen develops blood dynamic conditions that allows a sluggish blood flow so that cells involved in immunological processes can proliferate and differentiate and it also contributes to the trapping of lymphocytes to the area through the differentiation of typical characteristics of HEV endothelial cells.