Biomedical subjects

Mike Salmon

Publications and source records attributed to Mike Salmon.

At least 19 recordsLinked to original sources

PubMed2006

Differential survival of leukocyte subsets mediated by synovial, bone marrow, and skin fibroblasts: site-specific versus activation-dependent survival of T cells and neutrophils.

OBJECTIVE: Synovial fibroblasts share a number of phenotype markers with fibroblasts derived from bone marrow. In this study we investigated the role of matched fibroblasts obtained from 3 different sources (bone marrow, synovium, and skin) to test the hypothesis that synovial fibroblasts share similarities with bone marrow-derived fibroblasts in terms of their ability to support survival of T cells and neutrophils. METHODS: Matched synovial, bone marrow, and skin fibroblasts were established from 8 different patients with rheumatoid arthritis who were undergoing knee or hip surgery. Resting or activated fibroblasts were cocultured with either CD4 T cells or neutrophils, and the degree of leukocyte survival, apoptosis, and proliferation were measured. RESULTS: Fibroblasts derived from all 3 sites supported increased survival of CD4 T cells, mediated principally by interferon-beta. However, synovial and bone marrow fibroblasts shared an enhanced site-specific ability to maintain CD4 T cell survival in the absence of proliferation, an effect that was independent of fibroblast activation or proliferation but required direct T cell-fibroblast cell contact. In contrast, fibroblast-mediated neutrophil survival was less efficient, being independent of the site of origin of the fibroblast but dependent on prior fibroblast activation, and mediated solely by soluble factors, principally granulocyte-macrophage colony-stimulating factor. CONCLUSION: These results suggest an important functional role for fibroblasts in the differential accumulation of leukocyte subsets in a variety of tissue microenvironments. The findings also provide a potential explanation for site-specific differences in the pattern of T cell and neutrophil accumulation observed in chronic inflammatory diseases.

Apoptosis↗

PubMed2006

Treating very early rheumatoid arthritis.

Rheumatoid arthritis (RA) is common and leads to joint damage due to persistent synovitis. The persistence of inflammation is maintained by hyperplastic stromal tissue, which drives the accumulation of leukocytes in the synovium. Aggressive treatment after the first 3-4 months of symptoms, with either disease modifying anti-rheumatic drugs or anti-tumor necrosis factor (TNF)-alpha therapy, reduces the rate of disease progression. However, it rarely switches off disease such that remission can be maintained without the continued need for immunosuppressive therapy. There is increasing evidence that the first few months after symptom onset represent a pathologically distinct phase of disease. This very early phase may translate into a therapeutic window of opportunity during which it may be possible to permanently switch off the disease process. The rationale for, and approaches to, treatment within this very early window are discussed.

Antibodies↗

PubMed2006

Synovial fluid leukocyte apoptosis is inhibited in patients with very early rheumatoid arthritis.

Synovial leukocyte apoptosis is inhibited in established rheumatoid arthritis (RA). In contrast, high levels of leukocyte apoptosis are seen in self-limiting crystal arthritis. The phase in the development of RA at which the inhibition of leukocyte apoptosis is first apparent, and the relationship between leukocyte apoptosis in early RA and other early arthritides, has not been defined. We measured synovial fluid leukocyte apoptosis in very early arthritis and related this to clinical outcome. Synovial fluid was obtained at presentation from 81 patients with synovitis of < or = 3 months duration. The percentages of apoptotic neutrophils and lymphocytes were assessed on cytospin preparations. Patients were assigned to diagnostic groups after 18 months follow-up. The relationship between leukocyte apoptosis and patient outcome was assessed. Patients with early RA had significantly lower levels of neutrophil apoptosis than patients who developed non-RA persistent arthritis and those with a resolving disease course. Similarly, lymphocyte apoptosis was absent in patients with early RA whereas it was seen in patients with other early arthritides. The inhibition of synovial fluid leukocyte apoptosis in the earliest clinically apparent phase of RA distinguishes this from other early arthritides. The mechanisms for this inhibition may relate to the high levels of anti-apoptotic cytokines found in the early rheumatoid joint (e.g. IL-2, IL-4, IL-15 GMCSF, GCSF). It is likely that this process contributes to an accumulation of leukocytes in the early rheumatoid lesion and is involved in the development of the microenvironment required for persistent RA.

Adult↗

PubMed2005

Cytomegalovirus-specific CD4+ T cells in healthy carriers are continuously driven to replicative exhaustion.

Repeated antigenic encounter drives proliferation and differentiation of memory T cell pools. An important question is whether certain specific T cells may be driven eventually to exhaustion in elderly individuals since the human life expectancy is increasing. We found that CMV-specific CD4+ T cells were significantly expanded in healthy young and old carriers compared with purified protein derivative-, varicella zoster virus-, EBV-, and HSV-specific populations. These CMV-specific CD4+ T cells exhibited a late differentiated phenotype since they were largely CD27 and CD28 negative and had shorter telomeres. Interestingly, in elderly CMV-seropositive subjects, CD4+ T cells of different specificities were significantly more differentiated than the same cells in CMV-seronegative individuals. This suggested the involvement of bystander-secreted, differentiation-inducing factors during CMV infection. One candidate was IFN-alpha, which induced loss of costimulatory receptors and inhibited telomerase in activated CD4+ T cells and was secreted at high levels by CMV-stimulated plasmacytoid dendritic cells (PDC). The CMV-specific CD4+ T cells in elderly subjects had severely restricted replicative capacity. This is the first description of a human memory T cell population that is susceptible to being lost through end-stage differentiation due to the combined effects of lifelong virus reactivation in the presence of bystander differentiation-inducing factors.

Adult↗

PubMed2005

Identification of a phenotypically and functionally distinct population of long-lived neutrophils in a model of reverse endothelial migration.

Recent studies have demonstrated that neutrophils are not a homogenous population of cells. Here, we have identified a subset of human neutrophils with a distinct profile of cell-surface receptors [CD54(high), CXC chemokine receptor 1(low) (CXCR1(low))], which represent cells that have migrated through an endothelial monolayer and then re-emerged by reverse transmigration (RT). RT neutrophils, when in contact with endothelium, were rescued from apoptosis, demonstrate functional priming, and were rheologically distinct from neutrophils that had not undergone transendothelial migration. In vivo, 1-2% of peripheral blood neutrophils in patients with systemic inflammation exhibit a RT phenotype. A smaller population existed in healthy donors ( approximately 0.25%). RT neutrophils were distinct from naïve circulatory neutrophils (CD54(low), CXCR1(high)) and naïve cells after activation with formyl-Met-Leu-Phe (CD54(low), CXCR1(low)). It is important that the RT phenotype (CD54(high), CXCR1(low)) is also distinct from tissue-resident neutrophils (CD54(low), CXCR1(low)). Our results demonstrate that neutrophils can migrate in a retrograde direction across endothelial cells and suggest that a population of tissue-experienced neutrophils with a distinct phenotype and function are present in the peripheral circulation in humans in vivo.

Apoptosis↗

PubMed2005

Interaction between integrin alpha9beta1 and vascular cell adhesion molecule-1 (VCAM-1) inhibits neutrophil apoptosis.

According to the prevailing paradigm, neutrophils are short-lived cells that undergo spontaneous apoptosis within 24 hours of their release from the bone marrow. However, neutrophil survival can be significantly prolonged within inflamed tissue by cytokines, inflammatory mediators, and hypoxia. During screening experiments aimed at identifying the effect of the adhesive microenvironment on neutrophil survival, we found that VCAM-1 (CD106) was able to delay both spontaneous and Fas-induced apoptosis. VCAM-1-mediated survival was as efficient as that induced by the cytokine IFN-beta and provided an additive, increased delay in apoptosis when given in combination with IFN-beta. VCAM-1 delivered its antiapoptotic effect through binding the integrin alpha9beta1. The alpha9beta1 signaling pathway shares significant features with the IFN-beta survival signaling pathway, requiring PI3 kinase, NF-kappaB activation, as well as de novo protein synthesis, but the kinetics of NF-kappaB activation by VCAM-1 were slower and more sustained compared with IFN-beta. This study demonstrates a novel functional role for alpha9beta1 in neutrophil biology and suggests that adhesive signaling pathways provide an important extrinsic checkpoint for the resolution of inflammatory responses in tissues.

Apoptosis↗

PubMed2005

The impact of telomere erosion on memory CD8+ T cells in patients with X-linked lymphoproliferative syndrome.

Patients with X-linked lymphoproliferative syndrome (XLP) experience excessive T cell proliferation after primary Epstein-Barr virus (EBV) infection, due to mutations in the signalling lymphocyte activation molecule (SLAM) associated protein (SAP) molecule. We examined the impact of dysfunctional proliferative control on the extent of CD8+ T cell differentiation in XLP patients who recovered from primary EBV infection. Although these young patients have normal numbers of lytic and latent EBV-epitope-specific CD8+ T cells, they were extremely differentiated as defined by loss of CCR7 and CD27, low telomerase activity and very short telomeres. This was not a direct effect arising from the loss of SAP, but was due to excessive T cell stimulation due to this defect. Thus, transduction of XLP CD8+ T cells with the catalytic component of telomerase (hTERT), but not SAP, prevented telomere loss and considerably extended proliferative lifespan in vitro. These results indicate that excessive proliferation in CD8+ T cells in XLP patients may lead to end-stage differentiation and loss of functional EBV-specific CD8+ T cells through replicative senescence. This may contribute to the defective immunity found in XLP patients who survive acute EBV infection who develop EBV-related B cell lymphomas before the fourth decade of life.

Adult↗

PubMed2005

Early rheumatoid arthritis is characterized by a distinct and transient synovial fluid cytokine profile of T cell and stromal cell origin.

Pathological processes involved in the initiation of rheumatoid synovitis remain unclear. We undertook the present study to identify immune and stromal processes that are present soon after the clinical onset of rheumatoid arthritis (RA) by assessing a panel of T cell, macrophage, and stromal cell related cytokines and chemokines in the synovial fluid of patients with early synovitis. Synovial fluid was aspirated from inflamed joints of patients with inflammatory arthritis of duration 3 months or less, whose outcomes were subsequently determined by follow up. For comparison, synovial fluid was aspirated from patients with acute crystal arthritis, established RA and osteoarthritis. Rheumatoid factor activity was blocked in the synovial fluid samples, and a panel of 23 cytokines and chemokines measured using a multiplex based system. Patients with early inflammatory arthritis who subsequently developed RA had a distinct but transient synovial fluid cytokine profile. The levels of a range of T cell, macrophage and stromal cell related cytokines (e.g. IL-2, IL-4, IL-13, IL-17, IL-15, basic fibroblast growth factor and epidermal growth factor) were significantly elevated in these patients within 3 months after symptom onset, as compared with early arthritis patients who did not develop RA. In addition, this profile was no longer present in established RA. In contrast, patients with non-rheumatoid persistent synovitis exhibited elevated levels of interferon-gamma at initiation. Early synovitis destined to develop into RA is thus characterized by a distinct and transient synovial fluid cytokine profile. The cytokines present in the early rheumatoid lesion suggest that this response is likely to influence the microenvironment required for persistent RA.

Adult↗

PubMed2005

Analysis of host response to bacterial infection using error model based gene expression microarray experiments.

A key step in the analysis of microarray data is the selection of genes that are differentially expressed. Ideally, such experiments should be properly replicated in order to infer both technical and biological variability, and the data should be subjected to rigorous hypothesis tests to identify the differentially expressed genes. However, in microarray experiments involving the analysis of very large numbers of biological samples, replication is not always practical. Therefore, there is a need for a method to select differentially expressed genes in a rational way from insufficiently replicated data. In this paper, we describe a simple method that uses bootstrapping to generate an error model from a replicated pilot study that can be used to identify differentially expressed genes in subsequent large-scale studies on the same platform, but in which there may be no replicated arrays. The method builds a stratified error model that includes array-to-array variability, feature-to-feature variability and the dependence of error on signal intensity. We apply this model to the characterization of the host response in a model of bacterial infection of human intestinal epithelial cells. We demonstrate the effectiveness of error model based microarray experiments and propose this as a general strategy for a microarray-based screening of large collections of biological samples.

Bacterial Infections↗

PubMed2005

Quiescence and functional reprogramming of Epstein-Barr virus (EBV)-specific CD8+ T cells during persistent infection.

After acute infection Epstein-Barr virus (EBV)-specific memory CD8+ T cells exit cell cycle, and a proportion of these antigen-experienced cells re-express CD45RA (CD45 which predominantly express exon A). However, the signals involved are not known. We investigated the roles of interleukin 15 (IL-15) and interferon-alpha/beta (IFN-I) in these processes, since these mediators have a crucial but undefined role in the maintenance of CD8+ T-cell memory. We show that IFN-I (but not IL-15) allows activated EBV-specific CD8+ T cells to leave cell cycle without entering apoptosis. This was associated with up-regulation of the cyclin inhibitor p27, but not of CD45RA. In contrast, IL-15 (but not IFN-I) induced "homeostatic" proliferation and CD45RA re-expression by these cells in vitro. Different signals, therefore, induce quiescence and CD45RA re-expression in activated EBV-specific CD8+ T cells. After T-cell receptor (TCR) activation freshly isolated CD45RA+ antigen-experienced CD8+ T cells show poor proliferative activity but are highly cytotoxic and secrete IFN-gamma efficiently. This suggests functional reprogramming toward effector function but away from proliferation. The induction of quiescence and the generation of proliferation-independent effector CD8+ T cells that re-express CD45RA may minimize the impact of replicative senescence in virus-specific populations that would otherwise occur during decades of persistent infection.

CD8-Positive T-Lymphocytes↗

PubMed2005

A chemokine-dependent stromal induction mechanism for aberrant lymphocyte accumulation and compromised lymphatic return in rheumatoid arthritis.

According to the current model for tissue-specific homing, specificity is conferred by the selective recruitment of lymphocyte populations from peripheral blood, based on their expression of chemokine and adhesion receptors (endothelial selection). In this study, we provide evidence for an alternative stromal induction mechanism that operates in chronic inflammation. We show that the human rheumatoid synovial microenvironment directly induces functional inflammatory (CCR5 and CXCR3) and constitutive (CCR7 and CXCR4) chemokine receptors on infiltrating CD4(+) T cells. Expression of the corresponding inflammatory chemokine ligands (CCL5 and CXCL11) was confined to stromal areas in the synovium. However, expression of the constitutive ligands (CCL19 and CXCL12) was inappropriately high on both vascular and lymphatic endothelium, suggesting that the vascular to lymphatic chemokine gradient involved in lymphatic recirculation becomes subverted in the rheumatoid synovium. These results challenge the view that leukocyte trafficking is regulated solely by selective recruitment of pre-existing chemokine receptor-positive cells from peripheral blood, by providing an alternative explanation based on aberrant lymphocyte retention and compromised lymphatic return.

Arthritis, Rheumatoid↗

PubMed2005

The role of leukocyte-stromal interactions in chronic inflammatory joint disease.

Rheumatoid arthritis (RA) is a debilitating, chronic, persistent inflammatory disease that is characterised by painful and swollen joints. The aetiology of RA is unknown, however whereas past research has concentrated on the role of immune or inflammatory infiltrating cells in inflammation, it is becoming clear that stromal cells play a critical part in regulating the quality and duration of an inflammatory response. In this review we assess the role of fibroblasts within the inflamed synovium in modulating immune responses; in particular we examine the role of stromal cells in the switch from resolving to persistent inflammation as is found in the rheumatoid synovium.

Animals↗

PubMed2005

Generation and characterization of novel stromal specific antibodies.

Rheumatoid synovial fibroblasts were used as an immunogen to produce monoclonal antibodies selected for their reactivity with stromal cell antigens. Mice were immunised with low passage whole cell preparations and the subsequent hybridomas were screened by immunohistochemistry on rheumatoid synovium and tonsil sections. The aim was to identify those antibodies that recognised antigens that were restricted to stromal cells and were not expressed on CD45 positive leucocytes. A significant number of antibodies detected antigen that identified endothelial cells. These antibodies were further characterised to determine whether the vessels identified by these antibodies were vascular or lymphatic. From five fusions clones were identified with predominant reactivity with: 1) fibroblasts and endothelial cells; or 2) broad stromal elements (fibroblast, endothelium, epithelium, follicular dendritic cells). A fibroblast-specific antibody that did not also identify vessels was not generated. Examples of each reactivity pattern are discussed.

Animals↗

PubMed2005

Multiplex bead immunoassay analysis of aqueous humor reveals distinct cytokine profiles in uveitis.

PURPOSE: To extensively characterize the complex network of cytokines present in uveitis aqueous humor (AqH), and the relationships between cytokines and the cellular infiltrate. METHODS: AqH from noninflammatory control subjects and patients with idiopathic, Fuchs' heterochromic cyclitis (FHC), and herpes-viral or Behçet's uveitis were analyzed for IL-1beta, -2, -4, -5, -7, -8, -10, -12, -13, -15, TNFalpha, IFNgamma, CCL2 (MCP-1), CCL5 (RANTES), CCL11 (Eotaxin), TGFbeta2, and CXCL12 (SDF-1), using multiplex bead immunoassays. The cellular infiltrate was also determined for each sample. RESULTS: Idiopathic uveitis AqH, compared with noninflammatory controls, was characterized by high levels of IL-6, IL-8, CCL2 and IFNgamma, the levels of which correlated with each other. For IL-6 and IL-8 these levels were proportional to the number of neutrophils present. By contrast, the levels of both TGFbeta2 and CXCL12 decreased in idiopathic uveitis AqH with increasing inflammation. Cluster analysis showed a degree of segregation between noninflammatory and idiopathic uveitis AqH. Further examination using random forest analysis yielded a complete distinction between these two groups. The minimum cytokines required for this classification were IL-6, IL-8, CCL2, IL-13, TNFalpha, and IL-2. CONCLUSIONS: Application of multiplex bead immunoassays has allowed us to identify distinct patterns of cytokines that relate to both clinical disease and the cellular infiltrates present. Bioinformatics analysis allowed identification of cytokines that differentiate idiopathic uveitis from noninflammatory control AqH and are likely to be important for the pathogenesis of uveitis.

Adolescent↗

PubMed2005

Predictive value of antibodies to cyclic citrullinated peptide in patients with very early inflammatory arthritis.

OBJECTIVE: To study the prognostic value of antibodies to cyclic citrullinated peptide (anti-CCP) and rheumatoid factor (RF), alone and in combination, in patients with very early synovitis. METHODS: A cross-sectional study was performed in patients with established inflammatory and noninflammatory disease to validate the assay in our unit and confirm previously reported sensitivities and specificities of anti-CCP antibodies. Subsequently, patients with synovitis of 3 months' duration were followed for 72 weeks and the ability of anti-CCP antibodies and RF to predict the development of rheumatoid arthritis (RA) and persistent inflammatory arthritis was assessed. RESULTS: One hundred twenty-four patients were assessed in the initial cross-sectional study. Anti-CCP antibodies and RF were detected by ELISA in only 4% of patients with non-RA inflammatory disease and in no patient with noninflammatory disease. Ninety-six patients with very early synovitis were assessed longitudinally. In these patients with early arthritis, the combination of anti-CCP antibodies and RF had a specificity, positive predictive value (PPV), sensitivity, and negative predictive value (NPV) for a diagnosis of RA of 100%, 100%, 58%, and 88%, respectively. The specificity, PPV, sensitivity, and NPV of this antibody combination for the development of persistent disease-fulfilling classification criteria for RA were 97%, 86%, 63%, and 91%, respectively. CONCLUSION: In patients with synovitis of 3 months' duration, a combination of anti-CCP antibodies and RF has a high specificity and PPV for the development of persistent RA. This autoantibody combination can be used to identify patients with disease destined to develop RA who may be appropriate for very early intervention.

Adult↗

PubMed2004

Chemokine receptors in the rheumatoid synovium: upregulation of CXCR5.

In patients with rheumatoid arthritis (RA), chemokine and chemokine receptor interactions play a central role in the recruitment of leukocytes into inflamed joints. This study was undertaken to characterize the expression of chemokine receptors in the synovial tissue of RA and non-RA patients. RA synovia (n = 8) were obtained from knee joint replacement operations and control non-RA synovia (n = 9) were obtained from arthroscopic knee biopsies sampled from patients with recent meniscal or articular cartilage damage or degeneration. The mRNA expression of chemokine receptors and their ligands was determined using gene microarrays and PCR. The protein expression of these genes was demonstrated by single-label and double-label immunohistochemistry. Microarray analysis showed the mRNA for CXCR5 to be more abundant in RA than non-RA synovial tissue, and of the chemokine receptors studied CXCR5 showed the greatest upregulation. PCR experiments confirmed the differential expression of CXCR5. By immunohistochemistry we were able to detect CXCR5 in all RA and non-RA samples. In the RA samples the presence of CXCR5 was observed on B cells and T cells in the infiltrates but also on macrophages and endothelial cells. In the non-RA samples the presence of CXCR5 was limited to macrophages and endothelial cells. CXCR5 expression in synovial fluid macrophages and peripheral blood monocytes from RA patients was confirmed by PCR. The present study shows that CXCR5 is upregulated in RA synovial tissue and is expressed in a variety of cell types. This receptor may be involved in the recruitment and positioning of B cells, T cells and monocytes/macrophages in the RA synovium. More importantly, the increased level of CXCR5, a homeostatic chemokine receptor, in the RA synovium suggests that non-inflammatory receptor-ligand pairs might play an important role in the pathogenesis of RA.

Adult↗

PubMed2004

Hepatic endothelial CCL25 mediates the recruitment of CCR9+ gut-homing lymphocytes to the liver in primary sclerosing cholangitis.

Primary sclerosing cholangitis (PSC), a chronic inflammatory liver disease characterized by progressive bile duct destruction, develops as an extra-intestinal complication of inflammatory bowel disease (IBD) (Chapman, R.W. 1991. Gut. 32:1433-1435). However, the liver and bowel inflammation are rarely concomitant, and PSC can develop in patients whose colons have been removed previously. We hypothesized that PSC is mediated by long-lived memory T cells originally activated in the gut, but able to mediate extra-intestinal inflammation in the absence of active IBD (Grant, A.J., P.F. Lalor, M. Salmi, S. Jalkanen, and D.H. Adams. 2002. Lancet. 359:150-157). In support of this, we show that liver-infiltrating lymphocytes in PSC include mucosal T cells recruited to the liver by aberrant expression of the gut-specific chemokine CCL25 that activates alpha4beta7 binding to mucosal addressin cell adhesion molecule 1 on the hepatic endothelium. This is the first demonstration in humans that T cells activated in the gut can be recruited to an extra-intestinal site of disease and provides a paradigm to explain the pathogenesis of extra-intestinal complications of IBD.

Cell Movement↗

PubMed2004

Inhibition of T cell apoptosis in the aqueous humor of patients with uveitis by IL-6/soluble IL-6 receptor trans-signaling.

A fundamental mechanism of immune privilege in the eye is the induction of T lymphocyte apoptosis. Intraocular inflammation in uveitis implies compromise of immune privilege. This study sought to determine whether apoptosis of T cells is actively inhibited in patients with uveitis and by what pathways this may occur. Apoptotic lymphocytes were found to be absent from aqueous humor (AqH) of virtually all patients with recent-onset uveitis. However, T cells removed from the eye were highly susceptible to both spontaneous and Fas ligand-induced apoptosis in vitro. AqH from patients with uveitis had no modulatory effect on Fas ligand-induced apoptosis, but strongly suppressed survival factor deprivation-induced apoptosis. In contrast, noninflammatory AqH from patients undergoing cataract surgery had no modulatory effects on apoptosis at all. These data suggest that triggering of the Fas pathway is diminished in uveitis, and also that homeostatic resolution through survival factor deprivation-induced apoptosis is inhibited by factors present in AqH. The most widely recognized pathways, common gamma-chain cytokines and type I IFNs, did not contribute to AqH-mediated T cell survival. High levels of both IL-6 and soluble IL-6R were found in AqH. IL-6 alone did not induce T cell survival, because IL-6R expression on T cells in AqH was too low to facilitate signaling. However, combinations of IL-6 and soluble IL-6R were highly effective inhibitors of T cell apoptosis, suggesting that the trans-signaling pathway is likely to be a key mediator of T cell apoptosis inhibition mediated by uveitis AqH.

Adolescent↗