Lymphoid stroma in health and disease

Summary Secondary lymphoid organs (SLOB), such as lymph nodes and spleen, are the sites where primary immune responses are initiated. T lymphocytes patrol through the blood and SLOs on the search for pathogens which are presented to them as antigens by dendritic cells. Stromal cells in the Tzone - so called T zone fibroblastic reticular cells (TRCs) -are critical in organizing the migration of T cells and dendritic cells by producing the chemoattractants CCL19 and CCL21 and by forming a network which T cells use as a guidance system. They also form a system of small channels or conduits that allow rapid transport of small antigen molecules or cytokines from the subcapsular sinus to high endothelial venules. The phenotype and function of TRCs have otherwise remained largely unknown. We found a critical role for lymph node access in CD4+ and CD8+ T cell homeostasis and identified TRCs within these organs as the major source of interleukin-7 (IL-7). IL-7 is an essential survival factor for naïve T lymphocytes of which the cellular source in the periphery had been poorly defined. In vitro, TRC were able to prevent the death of naïve T but not of B lymphocytes by secreting IL-7 and the CCR7 ligand CCL 19. Using gene-targeted mice, we show anon-redundant function of CCL19 in T cell homeostasis. The data suggest that TRCs regulate T cell numbers by providing a limited reservoir of survival factors for which T cells have to compete. They help to maintain a diverse T cell repertoire granting full immunocompetence. To determine whether TRCs also play a role in pathology, we characterized so-called tertiary lymphoid organs (TLOs) that often develop at sites of chronic inflammation. We show that TLOs resemble lymph nodes or Peyer's patches not only with regard to lymphoid cells. TLOs formed extensive TRC networks and a functional conduit system in all three marine inflammation models tested. In one model we dissected the cells and signals leading to the formation of these structures. We showed that they critically depend on the presence of lymphotoxin and lymphoid tissue inducer cells. TRCs in TLOs also produce CCL19, GCL21 and possibly IL-7 which are all involved in the development of TLOs. Stromal cells therefore play a central role in the onset and perpetuation of chronic inflammatory diseases and could be an interesting target for therapy. Résumé Le système immunitaire est la défense de notre corps contre toutes sortes d'infections et de tumeurs. II est constitué de différentes populations de lymphocytes qui patrouillent constamment le corps à la recherche de pathogène. Parmi eux, les lymphocytes T et B passent régulièrement dans les organes lymphoïdes secondaires (SLO) qui sont les sites d'initiation de la réponse immunitaire. Les lymphocytes T sont recrutés du sang aux SLO où ils cherchent leur antigène respectif présenté par des cellules dendritiques. Des cellules stromales dans la zone T -nommées fibroblastic reticular cells' (TRC) -sécrètent des chimiokines CCL19 et CCL21 et ainsi facilitent les rencontres entre lymphocytes T et cellules dendritiques. De plus, elles forment un réseau que les lymphocytes T utilisent comme système de guidage. Ce réseau forme des petits canaux (ou conduits) qui permettent le transport rapide, d'antigène soluble ou de cytokines, de la lymphe aux veinules à endothelium épais (HEV). Le phénotype ainsi que les autres fonctions des TRCs demeurent encore à ce jour inconnus. Nous avons trouvé que l'accès des lymphocytes T CD4+ et CD8+ aux ganglions joue un rôle central pour l'homéostasie. Interleukin-7 (IL-7) est un facteur de survie essentiel pour les lymphocytes T naïfs dont la source cellulaire dans la périphérie était mal définie. Nous avons identifié les TRCs dans les ganglions comme source principale d'interleukin-7 (IL-7). In vitro, les TRCs étaient capable de prévenir la mort des lymphocytes T mais pas celle de lymphocytes B grâce à la sécrétion d'IL-7 et de CCL19. En utilisant des souris déficientes du gène CCL19, nous avons observé que l'homéostasie des lymphocytes T dépend aussi de CCL19 in vivo. Les données suggèrent que les TRCs aident à maintenir un répertoire large et diversifié de cellules T et ainsi l'immunocompétence. Pour déterminer si les TRCs pourraient jouer un rote également dans la pathologie, nous avons caractérisé des organes lymphoïdes tertiaires (TLOs) souvent associés avec l'inflammation chronique. Les TLOs ressemblent à des ganglions ou des plaques de Peyer pas seulement en ce qui concerne la présence de lymphocytes. Nous avons constaté que les TLOs forment des réseaux de TRC et un système fonctionnel de conduits. La formation de ces structures est fortement diminuée dans l'absence du signal lymphotoxin ou des cellules connues comme ymphoid tissue-inducer tells: Les TRCs dans les TLOs produisent les chimiokines CCL19, CCL21 et possiblement aussi IL-7 qui sont impliquées dans le développement des TLOs. Les cellules stromales jouent donc un rôle central dans l'initation et la perpétuation des maladies inflamatoires chroniques et pourraient être une cible intéressante pour la thérapie.

Visualization of aqueous shunt position and patency using anterior segment optical coherence tomography.

PURPOSE: To describe the use of anterior segment optical coherence tomography (AS-OCT) to clarify the position and patency of aqueous shunt devices in the anterior chamber of eyes where corneal edema or tube position does not permit a satisfactory view. DESIGN: Noncomparative observational case series. METHODS: Four cases are reported in which aqueous shunt malposition or obstruction was suspected but the shunt could not be seen on clinical examination. The patients underwent AS-OCT to identify the position and patency of the shunt tip. RESULTS: In each case, AS-OCT provided data regarding tube position and/or patency that could not be obtained by slit-lamp examination or by gonioscopy that influenced management. CONCLUSIONS: AS-OCT can be used to visualize anterior chamber tubes in the presence of corneal edema that precludes an adequate view or in cases where the tube is retracted into the cornea. In such cases, AS-OCT is useful in identifying shunt patency and position, which helps guide clinical decision making.

Effect of atazanavir versus other protease inhibitor-containing antiretroviral therapy on endothelial function in HIV-infected persons: randomised controlled trial.

OBJECTIVE: Impaired endothelial function was demonstrated in HIV-infected persons on protease inhibitor (PI)-containing antiretroviral therapy, probably due to altered lipid metabolism. Atazanavir is a PI causing less atherogenic lipoprotein changes. This study determined whether endothelial function improves after switching from other PI to atazanavir. DESIGN: Randomised, observer-blind, treatment-controlled trial. SETTING: Three university-based outpatient clinics. PATIENTS: 39 HIV-infected persons with suppressed viral replication on PI-containing regimens and fasting low-density lipoprotein (LDL)-cholesterol greater than 3 mmol/l. INTERVENTION: Patients were randomly assigned to continue the current PI or change to unboosted atazanavir. MAIN OUTCOME MEASURES: Endpoints at week 24 were endothelial function assessed by flow-mediated dilation (FMD) of the brachial artery, lipid profiles and serum inflammation and oxidative stress parameters. RESULTS: Baseline characteristics and mean FMD values of the two treatment groups were comparable (3.9% (SD 1.8) on atazanavir versus 4.0% (SD 1.5) in controls). After 24 weeks' treatment, FMD decreased to 3.3% (SD 1.4) and 3.4% (SD 1.7), respectively (all p = ns). Total cholesterol improved in both groups (p<0.0001 and p = 0.01, respectively) but changes were more pronounced on atazanavir (p = 0.05, changes between groups). High-density lipoprotein and triglyceride levels improved on atazanavir (p = 0.03 and p = 0.003, respectively) but not in controls. Serum inflammatory and oxidative stress parameters did not change; oxidised LDL improved significantly in the atazanavir group. CONCLUSIONS: The switch from another PI to atazanavir in treatment-experienced patients did not result in improvement of endothelial function despite significantly improved serum lipids. Atherogenic lipid profiles and direct effects of antiretroviral drugs on the endothelium may affect vascular function. Trial registration number: NCT00447070.

Lung fluid movements in hypoxia.

Pulmonary edema is a problem of major clinical importance resulting from a persistent imbalance between forces that drive water into the airspace of the lung and the biological mechanisms for its removal. Here, we will first review the fundamental mechanisms implicated in the regulation of lung fluid homeostasis, namely, the Starling forces and the respiratory transepithelial sodium transport. Second, we will discuss the contribution of hypoxia to the perturbation of this fine balance and the role of such perturbations in the development of high-altitude pulmonary edema, a disease characterized by a very high morbidity and mortality. Finally, we will review possible interventions aimed to maintain/restore lung fluid homeostasis and their importance for the prevention/treatment of pulmonary edema.

The integrin antagonist cilengitide activates alphaVbeta3, disrupts VE-cadherin localization at cell junctions and enhances permeability in endothelial cells.

Cilengitide is a high-affinity cyclic pentapeptdic alphaV integrin antagonist previously reported to suppress angiogenesis by inducing anoikis of endothelial cells adhering through alphaVbeta3/alphaVbeta5 integrins. Angiogenic endothelial cells express multiple integrins, in particular those of the beta1 family, and little is known on the effect of cilengitide on endothelial cells expressing alphaVbeta3 but adhering through beta1 integrins. Through morphological, biochemical, pharmacological and functional approaches we investigated the effect of cilengitide on alphaVbeta3-expressing human umbilical vein endothelial cells (HUVEC) cultured on the beta1 ligands fibronectin and collagen I. We show that cilengitide activated cell surface alphaVbeta3, stimulated phosphorylation of FAK (Y(397) and Y(576/577)), Src (S(418)) and VE-cadherin (Y(658) and Y(731)), redistributed alphaVbeta3 at the cell periphery, caused disappearance of VE-cadherin from cellular junctions, increased the permeability of HUVEC monolayers and detached HUVEC adhering on low-density beta1 integrin ligands. Pharmacological inhibition of Src kinase activity fully prevented cilengitide-induced phosphorylation of Src, FAK and VE-cadherin, and redistribution of alphaVbeta3 and VE-cadherin and partially prevented increased permeability, but did not prevent HUVEC detachment from low-density matrices. Taken together, these observations reveal a previously unreported effect of cilengitide on endothelial cells namely its ability to elicit signaling events disrupting VE-cadherin localization at cellular contacts and to increase endothelial monolayer permeability. These effects are potentially relevant to the clinical use of cilengitide as anticancer agent.

Plasminogen activator inhibitor-1 activity and 4G/5G polymorphism in hemodialysis

Introduction: Chronic insufficiency alters homeostasis, in part due to endothelial inflammation. Plasminogen activator inhibitor-1 (PAI-1) is increased in renal disease, contributing to vascular damage. We assessed PAI-1 activity and PAI-1 4G/5G polymorphism in hemodialysis (HD) subjects and any association between thrombotic vascular access (VA) events and PAI-1 polymorphism. Methods: Prospective, observational study in 36 HD patients: mean age: 66.6 +/- 12.5 yr, males n=26 (72%), time on HD: 28.71 +/- 22.45 months. Vascular accesses: 10 polytetrafluoroethylene grafts (PTFEG), 22 arteriovenous fistulae (AVF), four dual lumen catheters (CAT). Control group (CG): 40 subjects; mean age: 60.0 +/- 15 yrs, males n=30 (75%). Group A (GA): thrombotic events (n=12), and group B (GB): No events (n=24). Groups were no different according to age (69.2 +/- 9.12 vs. 65.3 +/- 14.5 yrs), gender (males: 7; 58.3% vs. 18; 81.8%), time on HD (26.1 +/- 14.7 vs. 30.1 +/- 38.7 months), causes of renal failure. Time to follow-up, for access thrombosis: 12 months. Results: PAI-1 levels in HD: 7.21 +/- 2.13 vs. CG: 0.42 +/- 0.27 U/ml (p < 0.000 1). PAI-1 4G/5G polymorphic variant distribution in HD: 5G/5G: 6 (17%),4G/5G: 23 (64%); 4G/4G: 7 (19%) and in CG: 5G/5G: 14 (35%); 4G/5G: 18 (45%); 4G/4G: 8 (20%). C-reactive protein (CRP) in HD: 24.5 +/- 15.2 mg/L vs. in CG 2.3 +/- 0.2 mg/L (p < 0.0001). PAI-1 4G/5G variants: GA: 5G/5G: 3; 4G/5G: 8; 4G/4G: 1; GB: 5G/5G: 3; 4G/5G: 15; 4G/4G: 6. Thrombosis occurred in 8/10 patients (80%) with PTFEG, 3/22 (9%) in AVF, and 1/4 (25%) in CAT. Among the eight PTFEG patients with thrombosis, seven were PAI 4G/5G. Conclusions: PAI-1 levels were elevated in HD patients, independent of their polymorphic variants, 4G/5G being the most prevalent variant. Our data suggest that in patients with PTFEG the 4G/5G variant might be associated with an increased thrombosis risk.

High-density lipoprotein, beta cells, and diabetes .

High-density lipoproteins (HDLs) exert a series of potentially beneficial effects on many cell types including anti-atherogenic actions on the endothelium and macrophage foam cells. HDLs may also exert anti-diabetogenic functions on the beta cells of the endocrine pancreas, notably by potently inhibiting stress-induced cell death and enhancing glucose-stimulated insulin secretion. HDLs have also been found to stimulate insulin-dependent and insulin-independent glucose uptake into skeletal muscle, adipose tissue, and liver. These experimental findings and the inverse association of HDL-cholesterol levels with the risk of diabetes development have generated the notion that appropriate HDL levels and functionality must be maintained in humans to diminish the risks of developing diabetes. In this article, we review our knowledge on the beneficial effects of HDLs in pancreatic beta cells and how these effects are mediated. We discuss the capacity of HDLs to modulate endoplasmic reticulum stress and how this affects beta-cell survival. We also point out the gaps in our understanding on the signalling properties of HDLs in beta cells. Hopefully, this review will foster the interest of scientists in working on beta cells and diabetes to better define the cellular pathways activated by HDLs in beta cells. Such knowledge will be of importance to design therapeutic tools to preserve the proper functioning of the insulin-secreting cells in our body.

Extracellular superoxide dismutase is a major determinant of nitric oxide bioavailability: in vivo and ex vivo evidence from ecSOD-deficient mice.

The bioavailability of nitric oxide (NO) within the vascular wall is limited by superoxide anions (O2.-). The relevance of extracellular superoxide dismutase (ecSOD) for the detoxification of vascular O2.- is unknown. We determined the involvement of ecSOD in the control of blood pressure and endothelium-dependent responses in angiotensin II-induced hypertension and renovascular hypertension induced by the two-kidney, one-clip model in wild-type mice and mice lacking the ecSOD gene. Blood pressure was identical in sham-operated ecSOD+/+ and ecSOD-/- mice. After 6 days of angiotensin II-treatment and 2 and 4 weeks after renal artery clipping, blood pressure was significantly higher in ecSOD-/- than ecSOD+/+ mice. Recombinant ecSOD selectively decreased blood pressure in hypertensive ecSOD-/- mice, whereas ecSOD had no effect in normotensive and hypertensive ecSOD+/+ mice. Compared with sham-operated ecSOD+/+ mice, sham-operated ecSOD-/- mice exhibited attenuated acetylcholine-induced relaxations. These responses were further depressed in vessels from clipped animals. Vascular O2.-, as measured by lucigenin chemiluminescence, was higher in ecSOD-/- compared with ecSOD+/+ mice and was increased by clipping. The antioxidant tiron normalized relaxations in vessels from sham-operated and clipped ecSOD-/-, as well as from clipped ecSOD+/+ mice. In contrast, in vivo application of ecSOD selectively enhanced endothelium-dependent relaxation in vessels from ecSOD-/- mice. These data reveal that endogenous ecSOD is a major antagonistic principle to vascular O2.-, controlling blood pressure and vascular function in angiotensin II-dependent models of hypertension. ecSOD is expressed in such an abundance that even in situations of high oxidative stress no relative lack of enzyme activity occurs.

A new locus for congenital cataract, microcornea, microphthalmia, and atypical iris coloboma maps to chromosome 2.

OBJECTIVE: To report a novel phenotype of autosomal dominant atypical congenital cataract associated with variable expression of microcornea, microphthalmia, and iris coloboma linked to chromosome 2. Molecular analysis of this phenotype may improve our understanding of anterior segment development. DESIGN: Observational case study, genome linkage analysis, and gene mutation screening. PARTICIPANTS: Three families, 1 Egyptian and 2 Belgians, with a total of 31 affected were studied. METHODS: Twenty-one affected subjects and 9 first-degree relatives underwent complete ophthalmic examination. In the Egyptian family, exclusion of PAX6, CRYAA, and MAF genes was demonstrated by haplotype analysis using microsatellite markers on chromosomes 11, 16, and 21. Genome-wide linkage analysis was then performed using 385 microsatellite markers on this family. In the 2 Belgian families, the PAX6 gene was screened for mutations by direct sequencing of all exons. MAIN OUTCOME MEASURES: Phenotype description, genome-wide linkage of the phenotype, linkage to the PAX6, CRYAA, and MAF genes, and mutation detection in the PAX6 gene. RESULTS: Affected members of the 3 families had bilateral congenital cataracts inherited in an autosomal dominant pattern. A novel form of hexagonal nuclear cataract with cortical riders was expressed. Among affected subjects with available data, 95% had microcornea, 39% had microphthalmia, and 38% had iris coloboma. Seventy-five percent of the colobomata were atypical, showing a nasal superior location in 56%. A positive lod score of 4.86 was obtained at theta = 0 for D2S2309 on chromosome 2, a 4.9-Mb common haplotype flanked by D2S2309 and D2S2358 was obtained in the Egyptian family, and linkage to the PAX6, CRYAA, or MAF gene was excluded. In the 2 Belgian families, sequencing of the junctions and all coding exons of PAX6 did not reveal any molecular change. CONCLUSIONS: We describe a novel phenotype that includes the combination of a novel form of congenital hexagonal cataract, with variably expressed microcornea, microphthalmia, and atypical iris coloboma, not caused by PAX6 and mapping to chromosome 2. FINANCIAL DISCLOSURE(S): The authors have no proprietary or commercial interest in any materials discussed in this article.

Sex differences in atheroma burden and endothelial function in patients with early coronary atherosclerosis.

AIMS: Women and men have different clinical presentations and outcomes in coronary artery disease (CAD). We tested the hypothesis that sex differences may influence coronary atherosclerotic burden and coronary endothelial function before development of obstructive CAD. METHODS AND RESULTS: A total of 142 patients (53 men, 89 women; mean +/- SD age, 49.3 +/- 11.7 years) with early CAD simultaneously underwent intravascular ultrasonography and coronary endothelial function assessment. Atheroma burden in the left main and proximal left anterior descending (LAD) arteries was significantly greater in men than women (median, 23.0% vs. 14.1%, P = 0.002; median, 40.1% vs. 29.3%, P = 0.001, respectively). Atheroma eccentricity in the proximal LAD artery was significantly higher in men than women (median, 0.89 vs. 0.80, P = 0.04). The length of the coronary segments with endothelial dysfunction was significantly longer in men than women (median, 39.2 vs. 11.1 mm, P = 0.002). In contrast, maximal coronary flow reserve was significantly lower in women than men (2.80 vs. 3.30, P < 0.001). Sex was an independent predictor of atheroma burden in the left main and proximal LAD arteries (both P < 0.05) by multivariate analysis. CONCLUSION: Men have greater atheroma burden, more eccentric atheroma, and more diffuse epicardial endothelial dysfunction than women. These results suggest that men have more severe structural and functional abnormalities in epicardial coronary arteries than women, even in patients with early atherosclerosis, which may result in the higher incidence rates of CAD and ST-segment myocardial infarction in men than women.

Franceschetti hereditary recurrent corneal erosion.

PURPOSE: To describe new affected individuals of Franceschetti's original pedigree of hereditary recurrent erosion and to classify a unique entity called Franceschetti corneal dystrophy. DESIGN: Observational case series. METHODS: Slit-lamp examination of 10 affected individuals was conducted. Biomicroscopic examinations were supplemented by peripheral corneal biopsy in 1 affected patient with corneal haze. Tissue was processed for light and electron microscopy and immunohistochemistry was performed. DNA analysis was carried out in 12 affected and 3 nonaffected family members. RESULTS: All affected individuals suffered from severe ocular pain in the first decade of life, attributable to recurrent corneal erosions. Six adult patients developed bilateral diffuse subepithelial opacifications in the central and paracentral cornea. The remaining 4 affected individuals had clear corneas in the pain-free stage of the disorder. Histologic and immunohistochemical examination of the peripheral cornea in a single patient showed a subepithelial, avascular pannus. There was negative staining with Congo red. DNA analysis excluded mutations in the transforming growth factor beta-induced (TGFBI) gene and in the tumor-associated calcium signal transducer 2 (TACSTD2) gene. CONCLUSION: We have extended the pedigree of Franceschetti corneal dystrophy and elaborated its natural history on the basis of clinical examinations. A distinctive feature is the appearance of subepithelial opacities in adult life, accompanied by a decreased frequency of recurrent erosion attacks. Its clinical features appear to distinguish it from most other forms of dominantly inherited recurrent corneal erosion reported in the literature.

On the retinal toxicity of intraocular glucocorticoids.

Corticosteroids are hormones involved in many physiological responses such as stress, immune modulation, protein catabolism and water homeostasis. The subfamily of glucocorticoids is used systemically in the treatment of inflammatory diseases or allergic reactions. In the eye, glucocorticoides are used to treat macular edema, inflammation and neovascularization. The most commonly used glucocorticoid is triamcinolone acetonide (TA). The pharmaceutical formulation of TA is not adapted for intravitreal administration but has been selected by ophthalmologists because its very low intraocular solubility provides sustained effect. Visual benefits of intraocular TA do not clearly correlate with morpho-anatomical improvements, suggesting potential toxicity. We therefore studied, non-common, but deleterious effects of glucocorticoids on the retina. We found that the intravitreal administration of TA is beneficial in the treatment of neovascularization because it triggers cell death of endothelial cells of neovessels by a caspase-independent mechanism. However, this treatment is toxic for the retina because it induces a non-apoptotic, caspase-independent cell death related to paraptosis, mostly in the retinal pigmented epithelium cells and the Müller cells.

Pathogenesis of streptococcal and staphylococcal endocarditis.

Although streptococcal and S. aureus IE share the same primary site of infection, their pathogenesis and clinical evolution present several major differences. Streptococci adhere to cardiac valves with pre-existing endothelial lesions. In contrast, S. aureus can colonize either damaged endothelium or invade physically intact endothelial cells. These interactions are mediated by multiple surface adhesins, some of which have been only partially characterized. Streptococci produce surface glucans (gtf and ftf), ECM adhesins (e.g., fibronectin-binding proteins, FimA), and platelet aggregating factors (phase I and phase II antigens, pblA, pblB, and pblT), all of which have been.

Cardiovascular hypertrophy: role of angiotensin II and bradykinin.

Angiotensin II can raise blood pressure rapidly by inducing direct vasoconstriction and by activating the sympathetic nervous system via central and peripheral mechanisms. In addition, this peptide may act as a growth factor to cause vascular and cardiac hypertrophy (CVH). The structural changes caused by hypertension can therefore be amplified by angiotensin II. Blockade of angiotensin II generation with angiotensin-converting enzyme (ACE) inhibitors appears to be particularly effective in preventing the development of cardiovascular hypertrophy. This beneficial effect might be related to some extent to local accumulation of bradykinin. ACE is one of the enzymes physiologically involved in bradykinin degradation. Treatment of hypertensive rats with a selective bradykinin antagonist can attenuate the blood pressure-lowering effect of ACE inhibition and render less effective the prevention of intimal thickening after endothelial removal from the rat carotid artery. Bradykinin is a vasodilator that acts by increasing the release of endothelium-derived factors such as nitric oxide and prostacyclin, which may have antiproliferative activity. However, blockade of the renin-angiotensin system with an angiotensin II subtype 1-receptor antagonist is also effective in preventing cardiac hypertrophy and neointimal proliferation after endothelial injury. Therefore, the exact contribution of bradykinin to the beneficial effects of ACE inhibition on cardiovascular hypertrophy remains to be further explored.

New concepts in the pathophysiology of infective endocarditis.

Endocarditis pathogens colonize valves with pre-existing sterile vegetations or valves with minimal endothelial lesions. Inflamed endothelia produce cytokines, integrins, and tissue factor, which in turn attract fibronectin, monocytes, and platelets. Bacteria attaching to such structures further activate the cascade, becoming embedded and protected from host defenses. Staphylococcus aureus also actively invade the endothelium, causing apoptosis and endothelial damage. Knowledge of this interplay identifies host factors as potential therapeutic targets. Blocking infection by modulating host factors might be opportune because host factors are conserved. In contrast, interfering with bacterial virulence factors might be more complicated because they vary among different bacteria.