Development of Real-Time PCR for the Rapid Detection of Episomal Banana streak virus (BSV)

A real-time assay for the detection of episomal Banana streak virus (BSV; strain OL) in banana and plantains that carry integrated BSV sequences is described. Primers specific to the viral DNA were designed using the viral sequence integrated into the cv. Obino l'Ewai genome and the sequence of the genomic DNA of the infecting virus strain OL. They amplify a sequence of 1,336 bp that is detected in real-time by a short fluorogenic 3' minor groove binder DNA probe. This method enables reproducible and specific detection of episomal BSV from purified DNA as well as from crude extracts from infected plants. The assay is rapid, adaptable for large-scale experiments, and circumvents carryover problems.

Unilateral varicella zoster virus ophthalmicus and contralateral acute retinal necrosis

We report two patients who developed varicella zoster virus (VZV) ophthalmicus complicated by ipsilateral keratouveitis, and within 4 weeks developed acute retinal necrosis (ARN) in the contralateral eye. The ipsilateral retina was spared in each case. One patient had systemic lupus erythematosus (SLE) and the other Hodgkin's disease. Both patients were in remission at the time of presentation.

The death-inducing signalling complex is recruited to lipid rafts in Fas-induced apoptosis

Membrane microdomains known as lipid rafts have been shown recently to be involved in Fas signalling and apoptosis in T and B cell lines. Here, we have investigated further the role of lipid rafts in Fas-induced apoptosis in non-transformed human CD4 T cells. We show that Fas-induced apoptosis in CD4 T cells was inhibited by the lipid raft disrupter methyl-beta-cyclodextrin. When lipid rafts were isolated from control and Fas ligand treated cells, we found that a small proportion of Fas was present in the raft fraction in untreated cells and that this was greatly increased upon Fas ligation. The other components of the Death Inducing Signalling Complex (DISC), FADD, and procaspase 8, were also present at higher levels in the raft fraction isolated from Fas ligand treated cells. We conclude that formation of the DISC occurs in lipid rafts and that these membrane microdomains are required for efficient Fas signalling and apoptosis.

Epstein-Barr virus-specific CD8(+) T cells that re-express CD45RA are apoptosis-resistant memory cells that retain replicative potential

During acute infection, latent and lytic Epstein-Barr virus (EBV) epitope-specific CD8(+) T cells have a CD45RO(+) CD45RA(-) phenotype. However, after resolution of the infection, a large proportion of these cells, particularly those specific for lytic viral epitopes, re-express the CD45RA molecule. The role of CD8(+) CD45RA(+) T cells in ongoing immunity to EBV and other viruses is unknown. We now demonstrate that, relative to their CD45RO(+) counterparts, the EBV-specific CD8(+) T cells that revert to CD45RA expression after acute infectious mononucleosis are not in cell cycle, have longer telomeres, and are more resistant to apoptosis partly because of increased Bcl-2 expression. However, the EBV-specific CD8(+) CD45RA(+) T cells have shorter telomeres than the total CD8(+) CD45RA(+) T-cell pool and predominantly express low levels of the CCR7 chemokine receptor, indicating that they are not naive cells. In addition, EBV-specific CD8(+) CD45RA(+) T cells can be induced to proliferate and exhibit potent cytotoxic activity against target cells loaded with specific peptide. Our results strongly suggest, therefore, that EBV-specific CD8(+) CD45RA(+) T cells represent a stabilized virus-specific memory pool and not terminally differentiated effector cells. The identification of mechanisms that enable stable virus-specific CD8(+) T cells to persist after acute infection may lead to the enhancement of antiviral immunity in immunocompromised and elderly persons.

Evidence for a two pigment visual system in the fiddler crab, Uca thayeri

Intraocular recordings were made from the eyestalks of dark-adapted fiddler crabs (Uca thayeri) during presentation of monochromatic light flashes of different wavelengths and intensities. Two types of signals were recorded in different experiments: slow potentials (electroretinogram) and fast potentials (spikes). The latter were also recorded in the presence of a continuous green or red adapting light. The resulting visual spectral-sensitivity curves, when fitted to rhodopsin-based visual pigment absorption spectra (from Dartnall nomograms), indicated the presence of two visual pigments, one with an absorption maximum near 430 nm, and the other with a peak absorption between 500 nm and 540 nm. The data also provided evidence for some differential bleaching of the pigments in the presence of a colored adapting light, but most of the adaptation effect was probably due to changes in screening pigment and neural desensitization or inhibition. These two observations suggest that an adequate substrate for color vision may exist in this and other species of fiddler crabs. The electroretinogram and spike-recording methods produced similar visual-sensitivity data, suggesting that latter technique, a much more efficient way of collecting data that is physiologically relevant, may be the method of choice for determining spectral sensitivity in crustaceans.

Antigen-specific T cell suppression by human CD4+CD25+ regulatory T cells

Anergic/suppressive CD4+CD25+ T cells have been proposed to play an important role in the maintenance of peripheral tolerance. Here we demonstrate that in humans these cells suppress proliferation to self antigens, but also to dietary and foreign antigens. The suppressive CD4+CD25+ T cells display a broad usage of the T cell receptor Vbeta repertoire,suggesting that they recognize a wide variety of antigens. They reside in the primed/memory CD4+CD45RO+CD45RB(low) subset and have short telomeres, indicating that these cells have the phenotype of highly differentiated CD4+ T cells that have experienced repeated episodes of antigen-specific stimulation in vivo. This suggests that anergic/suppressive CD4+CD25+ T cells may be generated in the periphery as a consequence of repeated antigenic encounter. This is supported by the observation that highly differentiated CD4+T cells can be induced to become anergic/suppressive when stimulated by antigen presented by non-professional antigen-presenting cells. We suggest that besides being generated in the thymus, CD4+CD25+ regulatory T cells may also be generated in the periphery. This would provide a mechanism for the generation of regulatory cells that induce tolerance to a wide array of antigens that may not be encountered in the thymus.

Cytokine-mediated inhibition of apoptosis in non-transformed T cells and neutrophils can be dissociated from protein kinase B activation

In the absence of survival-inducing cytokines activated T cells and neutrophils enter apoptosis spontaneously. Phosphatidylinositol 3-kinase (PI3 K) activation and signaling through PKB/AKT have been widely linked to the inhibition of apoptosis by cytokines. Here we have investigated the role of PKB in the inhibition of spontaneous apoptosis of activated human CD4+ T cells and neutrophils. We used a range of cytokines known to induce survival and/or activation of PKB. We found activation of PKB in T cells treated with IL-2 and insulin, and neutrophils cultured with N-formyl-Met-Leu-Phe (fMLP), insulin or granulocyte-macrophage colony-stimulating factor. Insulin did not inhibit apoptosis in neutrophils or T cells and fMLP did not delay neutrophil apoptosis. Intriguingly, IFN-beta induced PI3 K-dependent survival in both cell types, but did not activate PKB. IL-2 mediated rescue of T cells from apoptosis but no induction of proliferation occurred in thepresence of LY294002, an inhibitor of PI3 K, which also blocked subsequent PKB activation. The main role of PI3 K in IL-2-mediated signaling may therefore be in the regulation of proliferation. These findings suggest that activation of PKB and inhibition of apoptosis can be dissociated in cytokine-mediated rescue of non-transformed CD4+ T cells and neutrophils.

Ectopic expression of the B cell-attracting chemokine BCA-1 (CXCL13) on endothelial cells and within lymphoid follicles contributes to the establishment of germinal center-like structures in Sjögren's syndrome

OBJECTIVE

To test the hypothesis that the formation of ectopic germinal center (GC)-like structures in Sjögren's syndrome (SS) is associated with the ectopic expression of the constitutive lymphoid tissue-homing chemokines B cell-attracting chemokine 1 (BCA-1; or, CXCL13) and stromal cell-derived factor 1 (SDF-1; or, CXCL12).

METHODS

Immunohistochemical and immunofluorescence analysis was used to determine the expression of the constitutive chemokines BCA-1 (CXCL13) and SDF-1 (CXCL12) in salivary glands from 5 SS patients and 3 non-SS patients. In addition, the expression of their respective receptors (CXCR5 and CXCR4) was examined on infiltrating lymphocytes. Human tonsil was used as a positive control for secondary lymphoid tissue.

RESULTS

BCA-1 (CXCL13) was expressed within lymphoid aggregates in SS, which shared many structural features with GCs in tonsil. BCA-1 (CXCL13) was completely absent in control biopsy samples from patients who did not have SS. High levels of BCA-1 (CXCL13) were also found on endothelial cells in salivary glands from SS patients. Diseased SS tissue was infiltrated by CXCR5-expressing B cells which organized into GC-like clusters. In complete contrast, SDF-1 (CXCL12), a constitutive chemokine involved in leukocyte retention within lymphoid tissue, was expressed by epithelial cells in both diseased and control samples. The chemokine receptor for SDF-1, CXCR4, was expressed on T cells that accumulated in a periductal distribution in diseased tissue.

CONCLUSION

The ectopic expression of BCA-1 (CXCL13) on endothelial cells and within GC-like structures, together with the strong expression of SDF-1 (CXCL12) on ductal epithelial cells, is a unique feature of inflamed glands in SS. By creating a local microenvironment supportive of focal B cell aggregation and differentiation, with structural features that are remarkably similar to GCs, BCA-1 (CXCL13) and SDF-1 (CXCL12) may contribute to the excessive production of high-affinity, class-switched autoantibodies and to the high incidence of B cell lymphomas classically associated with SS.

Neutrophil ageing and immunesenescence

As humans age, their morbidity and mortality from infection increases, their response to vaccination declines and they have an increased incidence of inflammatory diseases and cancer. The reasons for these effects are clearly complex, but reduced efficiency of the innate and adaptive immune system is likely to be important in the pathology of old age. Age-related changes in the adaptive immune system are well-documented and include alterations in T cell phenotype and effector functions and a reduced ability of B cells to produce high affinity antibody. In contrast, the innate immune system has been less well researched and the perception amongst many immunogerontologists is that this branch of the immune system is only moderately affected by age. However, it is becoming increasingly clear that the adaptive and innate immune systems co-operate at several levels to ensure the optimal immune response and any decline in adaptive immunity will impact upon the function of the innate immune system and vice-versa. Here, we review the literature concerning intrinsic age-related changes in neutrophil responses and consider how changes in lymphocyte function with age might further compromise efficiency of neutrophil function.

EBV-specific CD8+ T cell memory: relationships between epitope specificity, cell phenotype, and immediate effector function

EBV infection in humans induces CD8+ T cell memory to viral epitopes derived from both lytic and latent cycle Ags. We have analyzed the relationship between the phenotype and function of the memory pool of T cells specific for these Ags. Lytic epitope-specific populations were heterogeneous in terms of CD45RO/RA and CD28 expression, whereas latent epitope-specific populations were uniformly CD45RO+ and CD28+, consistent with the higher antigenic challenge from lytic epitopes driving some memory cells toward a CD45RA+, CD28- phenotype. However, both types of memory population showed immediate epitope-specific cytotoxicity and type 1 cytokine production in ex vivo assays. Cytotoxic function was not associated with preactivated T cells, as EBV-specific populations were negative for activation markers such as CD69 or CD38, nor could cytotoxic function be ascribed to CD27- or CD56+ subsets, as such cells were not detected in EBV-specific memory. Furthermore, cytotoxicity was not limited to CD45RA+ and/or CD28- fractions, but also was observed in CD45RO+, CD28+ populations in lytic and latent epitope-specific memory. Cytokine (IFN-gamma, TNF-alpha) responses, measured by intracytoplasmic staining after peptide stimulation, also were detectable in CD45RO+ and RA+ subsets as well as CD28+ and CD28- subsets. Of other markers that were heterogeneous in both lytic and latent epitope populations, CCR7 gave the best discrimination of functionality; thus, CCR7+ cells consistently failed to give an IFN-gamma or TNF-alpha response, whereas many CCR7- cells were responsive. Our data are consistent with effector functions having a broad distribution among phenotypically distinct subsets of "effector memory" cells that have lost the CCR7 marker.

Memory T cells constitute a subset of the human CD8+CD45RA+ pool with distinct phenotypic and migratory characteristics

Using HLA class I-viral epitope tetramers to monitor herpes virus-specific CD8(+) T cell responses in humans, we have shown that a significant fraction of responding cells revert from a CD45RO(+) to a CD45RA(+) state after priming. All tetramer-binding CD45RA(+) cells, regardless of epitope specificity, expressed a phenotype LFA-1(high)CCR7(low) that was stable for at least 10 years in infectious mononucleosis patients and indefinitely in asymptomatic carriers. CD8(+)CD45RA(+)LFA-1(high) cells were not present in cord blood but in adults account for up to 50% of CD8(+)CD45RA(+) cells. These CD45RA(+)LFA-1(high) cells have significantly shorter telomeres than CD45RA(+)LFA-1(low) cells, suggesting that the latter represent a naive population, while the former are memory cells. CD45RA(+) memory cells are a stable population of noncycling cells, but on stimulation they are potent producers of IFN-gamma, while naive CD8(+) cells produce only IL-2. The chemokine receptor profile and migratory potential of CD45RA(+) memory cells is very similar to CD45RO(+) cells but different to naive CD8 cells. In accord with this, CD45RA(+) memory cells were significantly underrepresented in lymph nodes, but account for virtually all CD8(+)CD45RA(+) T cells in peripheral tissues of the same individuals.

Hatching rhythms of Uca thayeri Rathbun: timing in semidiurnal and mixed tidal regimes

We compared the timing of larval release by Uca thayeri exposed to different tidal regimes. Crabs on Florida's East Coast experience semidiurnal tides, whereas crabs on the Florida's West Coast experience mixed tides.In both populations, hatching occurred shortly after high tide. On the East Coast, most crabs released their larvae between dusk and midnight, a few days before the maximum amplitude spring tides. On the West Coast, most crabs released their larvae during the afternoon tropic tides of greater amplitude. West Coast crabs may release during the day because ebbing tides at night are too weak for effective transport. Thus, at each location, hatching occurs when phase relationships between the ebbing tides, the light-dark cycle, and tidal amplitude are most favorable. Further study is required to determine whether females on each Coast show fixed responses to each tidal regime, or whether they can alter their hatching rhythms upon exposure to different tides.

Acoustic detection and communication by decapod crustaceans

This paper reviews behavioral, physiological, anatomical, and ecological aspects of sound and vibration detection by decapod crustaceans. Our intent is to demonstrate that despite very limited work in this area in the past 20 years, evidence suggests that at least some decapod crustaceans are able to detect and use sounds in ways that parallel detection and processing mechanisms in aquatic and terrestrial vertebrates. Some aquatic decapod crustaceans produce sounds, and many are able to detect substrate vibration at sensitivities sufficient to tell of the proximity of mates, competitors, or predators. Some semi-terrestrial crabs produce and use sounds for communication. These species detect acoustic stimuli as either air- or substrate-borne energies, socially interact in acoustic "choruses," and probably use "calls" to attract mates.

Fibroblasts regulate the switch from acute resolving to chronic persistent inflammation

Fibroblasts are important sentinel cells in the immune system and, here, it is proposed that these cells play a critical role in the switch from acute inflammation to adaptive immunity and tissue repair. It is suggested that chronic inflammation occurs because of disordered fibroblast behaviour in which failure to switch off their inflammatory programme leads to the inappropriate survival and retention of leukocytes within inflamed tissue.

Human anergic/suppressive CD4(+)CD25(+) T cells: a highly differentiated and apoptosis-prone population

Anergic/suppressive CD4(+)CD25(+) T cells exist in animal models but their presence has not yet been demonstrated in humans. We have identified and characterized a human CD4(+)CD25(+) T cell subset, which constitutes 7-10 % of CD4(+) T cells in peripheral blood and tonsil. These cells are a CD45RO(+)CD45RB(low) highly differentiated primed T cell population that is anergic to stimulation. Depletion of this small subset from CD4(+) T cells significantly enhances proliferation by threefold in the remaining CD4(+)CD25(-) T cells, while the addition of isolated CD4(+)CD25(+) T cells to CD4(+)CD25(-) T cells significantly inhibits proliferative activity. Blocking experiments suggest that suppression is not mediated via IL-4, IL-10 or TGF-beta and is cell-contact dependent. Isolated CD4(+)CD25(+) T cells are susceptible to apoptosis that is associated with low Bcl-2 expression, but this death can be prevented by IL-2 or fibroblast-secreted IFN-beta. However, the anergic/suppressive state of these cells is maintained after cytokine rescue. These human regulatory cells are therefore a naturally occurring, highly suppressive, apoptosis-prone population which are at a late stage of differentiation. Further studies into their role in normal and pathological situations in humans are clearly essential.

The flow cytometric analysis of telomere length in antigen-specific CD8+ T cells during acute Epstein-Barr virus infection

Acute infectious mononucleosis (AIM) induced by Epstein-Barr virus (EBV) infection is characterized by extensive expansion of antigen-specific CD8+ T cells. One potential consequence of this considerable proliferative activity is telomere shortening, which predisposes the EBV-specific cells to replicative senescence. To investigate this, a method was developed that enables the simultaneous identification of EBV specificity of the CD8+ T cells, using major histocompatibility complex (MHC) class I/peptide complexes, together with telomere length, which is determined by fluorescence in situ hybridization. Despite the considerable expansion, CD8+ EBV-specific T cells in patients with AIM maintain their telomere length relative to CD8+ T cells in normal individuals and relative to CD4+ T cells within the patients themselves and this is associated with the induction of the enzyme telomerase. In 4 patients who were studied up to 12 months after resolution of AIM, telomere lengths of EBV-specific CD8+ T cells were unchanged in 3 but shortened in one individual, who was studied only 5 months after initial onset of infection. Substantial telomere shortening in EBV-specific CD8+ T cells was observed in 3 patients who were studied between 15 months and 14 years after recovery from AIM. Thus, although telomerase activation may preserve the replicative potential of EBV-specific cells in AIM and after initial stages of disease resolution, the capacity of these cells to up-regulate this enzyme after restimulation by the persisting virus may dictate the extent of telomere maintenance in the memory CD8+ T-cell pool over time.

Differential regulation of CD8+ T cell senescence in mice and men

The cytotoxic CD8+ T cell population expands considerably during acute immune infection with virus. Most of these cells are removed by apoptosis at the end of the immune response. However, a balance has to be attained between clearance and retention of a memory population of cells, which respond more rapidly and efficiently to secondary encounter with the antigen. In this article, the role of apoptosis and in particular the development of replicative senescence as mechanisms which control this homeostatic balance are discussed. Although similar mechanisms regulate apoptosis in both humans and rodents, the available data suggests that replicative senescence may be controlled differently in these species, suggesting the there may be different constraints in the regulation of CD8+ T cell memory between different species.

Contribution of upregulated airway endothelin-1 expression to airway smooth muscle and epithelial cell DNA synthesis after repeated allergen exposure of sensitized Brown-Norway rats

Endothelin-1 is a potent bronchoconstrictor peptide with pro-inflammatory and growth-promoting properties. After exposure of sensitized Brown-Norway rats to six repeated ovalbumin exposures, there was an increase in pro-endothelin (ET)-1 messenger RNA compared with saline-exposed control rats 24 h after the final exposure (P < 0.01). ET-1 immunoreactivity was increased sixfold in the bronchial epithelium of the larger conducting airways in the repeated allergen-exposed rats (P < 0.001). After repeated allergen exposure, there were increased rates of DNA synthesis in the airway smooth muscle (ASM) cells (P < 0.001) and epithelial cells (P < 0. 001) compared with saline-exposed controls, as measured by bromodeoxyuridine incorporation. Treatment with a dual endothelin A and B (ET(A+B)) receptor antagonist caused a significant attenuation in both ASM (P < 0.001) and epithelial cell (P < 0.001) bromodeoxyuridine incorporation compared with the allergen-challenged and vehicle-treated group. The dual ET(A+B) antagonist attenuated eosinophil recruitment into the airways (P < 0. 05) but had no significant effect on increased bronchial reactivity to acetylcholine in allergen-exposed rats. Increased levels of ET-1 in the airways may contribute to inflammation and ASM and epithelial cell DNA synthesis after repeated allergen exposure. Such processes may underlie increased proliferation of resident cells leading to airway wall remodeling in asthmatics.

Regulation of neutrophil apoptosis: a role for protein kinase C and phosphatidylinositol-3-kinase

Neutrophils play a central role in host defense and are recruited in vast numbers to sites of infection where they phagocytose and kill invading bacterial pathogens. Neutrophils have a short half-life that is extended at the inflamed site by pro-inflammatory cytokines and contact with bacterial cell walls. Normal resolution of inflammation involves the removal of neutrophils and other inflammatory cells by the induction of apoptosis. Spontaneous neutrophil apoptosis does not require Fas ligation, but is mediated by caspases 3, 8 and possibly caspase 9 and also involves activation of protein kinase C-delta. With chronic inflammatory disease, neutrophil apoptosis is delayed by pro-inflammatory cytokines, leading to persistence of neutrophils at the inflamed site and non-specific tissue damage. Here we discuss the evidence for inhibition of neutrophil apoptosis via signaling though PI-3-kinase and downstream pathways, including PDK-1 and PKB. Therapeutic strategies to resolve chronic inflammation could therefore usefully target neutrophil apoptosis and the PI-3-kinase or PKC-delta signaling pathways.

Regulation of apoptosis and replicative senescence in CD8+ T cell following acute viral infection

Viral infections are characterised by a large expansion of CD8+ effector T cells. Once generated, these T cells must be cleared and homeostasis re-established. In this review we describe two mechanisms, apoptosis and replicative senescence which are thought to play a vital role in this process. Apoptosis clears the unwanted T cells at the end of an immune response whereas replicative senescence prevents unlimited expansion of T cells. For successful memory to be produced T cells must avoid apoptosis and avoid replicative senescence.

The inhibition of cutaneous T cell apoptosis may prevent resolution of inflammation in atopic eczema

Atopic eczema (AE) is characterized by the persistence of infiltrating T lymphocytes in the dermis. To test the hypothesis that dysregulation of normal T cell apoptosis may contribute to the pathogenesis and chronicity of AE we compared patients with a normal resolving immune response (Mantoux reaction (MR)) induced in healthy volunteers by cutaneous PPD injection. Significantly less T cell apoptosis was observed in lesional skin of AE patients compared with either the peak or the resolution phase of the MR (P < 0.0001). The low incidence of T cell apoptosis in AE was associated with significantly increased levels of Bcl-2 relative to Bax (P < 0.0001) and significantly decreased CD95-L expression (P < 0.002) compared with the resolving MR. The cytokines IL-15 and interferon-beta (IFN-beta), which prevent activated T cell apoptosis, were expressed maximally on day 7 and day 14 of the MR, respectively. In contrast, AE patients expressed high levels of both IL-15 and IFN-beta in cutaneous lesions at the same time. This suggests that the co-expression of two anti-apoptotic cytokines, which are not found together during resolving cutaneous responses, may contribute to excessive T cell survival which leads to the persistence of inflammation in patients with AE.

Type 1 IFN maintains the survival of anergic CD4+ T cells

Anergic T cells have immunoregulatory activity and can survive for extended periods in vivo. It is unclear how anergic T cells escape from deletion, because both anergy and apoptosis can occur after TCR ligation. Stimulation of human CD4+ T cell clones reactive to influenza hemagglutinin peptides can occur in the absence of APCs when MHC class II-expressing, activated T cells present peptide to each other. This T:T peptide presentation can induce CD95-mediated apoptosis, while the cells that do not die are anergic. We found that the death after peptide or anti-CD3 treatment of a panel of CD4+ T cell clones is blocked by IFN-beta secreted by fibroblasts and also by IFN-alpha. This increases cell recovery after stimulation, which is not due to T cell proliferation. This mechanism for apoptosis inhibition rapidly stops protein kinase C-delta translocation from the cytoplasm to the nucleus, which is an early event in the death process. A central observation was that CD4+ T cells that are rescued from apoptosis after T:T presentation of peptide by IFN-alphabeta remain profoundly anergic to rechallenge with Ag-pulsed APCs. However, anergized cells retain the ability to respond to IL-2, showing that they are nonresponsive but functional. The prevention of peptide-induced apoptosis in activated T cells by IFN-alphabeta is a novel mechanism that may enable the survival and maintenance of anergic T cell populations after TCR engagement. This has important implications for the persistence of anergic T cells with the potential for immunoregulatory function in vivo.

Persistent induction of the chemokine receptor CXCR4 by TGF-beta 1 on synovial T cells contributes to their accumulation within the rheumatoid synovium

Chemokines and their receptors determine the distribution of leukocytes within tissues in health and disease. We have studied the role of the constitutive chemokine receptor CXCR4 and its ligand, stromal-derived factor-1 (SDF-1) in the perivascular accumulation of T cells in rheumatoid arthritis. We show that synovial T cells, which are primed CD45RO+CD45RBdull cells and consequently not expected to express constitutive chemokine receptors, have high levels of the chemokine receptor CXCR4. Sustained expression of CXCR4 was maintained on synovial T cells by specific factors present within the synovial microenvironment. Extensive screening revealed that TGF-beta isoforms induce the expression of CXCR4 on CD4 T cells in vitro. Depletion studies using synovial fluid confirmed an important role for TGF-beta1 in the induction of CXCR4 expression in vivo. The only known ligand for CXCR4 is SDF-1. We found SDF-1 on synovial endothelial cells and showed that SDF-1 was able to induce strong integrin-mediated adhesion of synovial fluid T cells to fibronectin and ICAM-1, confirming that CXCR4 expressed on synovial T cells was functional. These results suggest that the persistent induction of CXCR4 on synovial T cells by TGF-beta1 leads to their active, SDF-1-mediated retention in a perivascular distribution within the rheumatoid synovium.

Increased expression of CD23 in rheumatoid synovitis

OBJECTIVE

Soluble (s)CD23 is a potent macrophage stimulator. High levels of this molecule have been reported in rheumatoid arthritis (RA) serum. We investigated the expression of CD23 and its ligands in rheumatoid synovial fluid and cells.

METHODS

Levels of sCD23, and cellular expression of CD23 and its ligands CD21, CD11b, and CD11c were measured in synovial fluid (SF) of RA patients and in blood of RA patients and controls.

RESULTS

SF contained higher levels of sCD23 than either rheumatoid or normal sera (median 4.8, 3.16,and 1.13 ng/ml respectively, p <0.01). Synovial CD23 was found to be expressed principally on macrophages. While little CD21 expression was detected, CD11b and CD11c were both expressed at high levels, particularly on macrophages.

CONCLUSIONS

Soluble CD23 is present in high levels in RA synovial fluid. Macrophages appear to be the principal source. Macrophages also express ligands for sCD23, and may therefore also be the targets of this potent pro-inflammatory molecule.

Racial origin and its effect on disease expression and HLA-DRB1 types in patients with rheumatoid arthritis: a matched cross-sectional study

OBJECTIVE

There are a significant number of patients with rheumatoid arthritis (RA) of North Indian or Pakistani origin (Asian) now living in the UK. RA has been poorly studied in this racial group. The aim of this study was to compare RA in this Asian group with RA in the indigenous northern European (European) population. It was hypothesized that these two racial groups would have different disease expressions and immunogenetics that could be relevant to pathogenesis, prognosis and therapy.

METHODS

One hundred and seven Asian RA patients, who fulfilled the 1987 American College of Rheumatology criteria, were stringently matched for age, sex and disease duration with 107 European RA patients, and were fully assessed.

RESULTS

The Asian RA patients had significantly fewer bony erosions [median Larsen score 58.5 (interquartile range 45.5-77.8) vs 68 (52-93) for European patients; P: = 0.0066, Mann-Whitney U:-test] and rarely had nodules (5.7 vs 20%, P: = 0. 0019, Fisher's exact test). The two groups had the same prevalence of rheumatoid factor positivity, number of swollen joints and level of inflammation (C-reactive protein). The Asian RA patients had a reduced prevalence of the conserved third allelic hypervariable region (3AHVR) (45 vs 82%, P: < 0.0001, Fisher's exact test), particularly DRB1*0401 (4.5 vs 55%). However, the prevalence of the conserved 3AHVR was significantly increased in the Asian RA patients compared with Asian controls. By contrast, the Asian patients had more tender joints [13.5 (7-22) vs 5.5 (2-11.8); P: < 0.0001 Mann-Whitney U:-test]. The Health Assessment Questionnaire score was also significantly worse in the Asians compared with the Europeans [median 2.0 (1.13-2.63) vs 1.25 (0.5-2.13), P: = 0.0001).

CONCLUSIONS

The Asian patients had similar levels of inflammation and less damage but more pain and disability than the matched European RA patients. Of the known prognostic factors for erosions (rheumatoid factor, conserved 3AHVR, swollen joints and C-reactive protein), only the conserved 3AHVR was reduced in the Asian RA patients, and this was consistent with their less erosive disease. These data also indicate the importance of pain as well as erosive damage in determining disability in Asian patients and stress the importance of adequate pain relief, in addition to disease suppression, when treating Asian RA patients.

Involvement of haemoxygenase-1 in ozone-induced airway inflammation and hyperresponsiveness

Haemoxygenase catalyses the degradation of haem to bilirubin, and the inducible form of haemoxygenase, haemoxygenase-1, is highly induced in response to oxidative stress in vitro. The effect of haemoxygenase-1 in oxidant stress in vivo is not known. We determined the effect of exposure to ozone on haemoxygenase-1 expression, and the modulation of haemoxygenase-1 expression on ozone-induced lung neutrophilia and bronchial hyperresponsiveness in rats. Ozone caused a significant induction of lung haemoxygenase-1. Pretreatment of rats with haemoglobin, a potent inducer of haemoxygenase-1, resulted in a large induction of haemoxygenase-1 expression, and inhibited ozone-induced neutrophilia and bronchial hyperresponsiveness. Tin protoporphyrin, a competitive inhibitor of haemoxygenase, reduced the expression of haemoxygenase-1 induced by haemoglobin. It enhanced ozone-induced neutrophilia, but not the bronchial hyperresponsiveness, and reduced the protective effect of haemoglobin. Overall, there was an association between bronchial hyperresponsiveness and the neutrophilic response. These data indicate that haemoxygenase-1 plays an important role in modulating the effects of an oxidant, such as ozone in the lungs.

Loss of CD28 expression on CD8(+) T cells is induced by IL-2 receptor gamma chain signalling cytokines and type I IFN, and increases susceptibility to activation-induced apoptosis

CD8(+)CD28(-) T cells are selectively expanded during viral infections, indicating their importance in anti-viral immune responses. Since little is known about the differentiation of CD8(+)CD28(-) cells, we investigated the generation, function and survival characteristics of this subset. In healthy individuals CD8(+)CD28(-) T cells contained more elevated levels of perforin and IFN-gamma than the CD8(+)CD28(+) subset, indicating that they can have an effector function. CD8(+)CD28(-) cells were selectively expanded when activated CD8(+)CD28(+) T cells were cultured in IL-2, IL-7 or IL-15. Moreover, the generation of CD8(+)CD28(-) cells was accelerated by type I IFN suggesting that these cytokines which are released during viral infections influence CD8(+) T cell differentiation. We did not observe re-expression of CD28 by CD8(+)CD28(-) T cells in any of the experiments performed. Activated T cells are susceptible to activation-induced cell death (AICD) if re-stimulated in the absence of co-stimuli. AICD was induced in both CD28(+) and CD28(-) subsets of activated T cells when stimulated with anti-CD3 antibody in the absence of co-stimuli but the magnitude of death was greater in the CD28(-) subset. While co-stimulation through LFA-1 (CD11a and CD18) significantly reduced AICD in the CD8(+)CD28(+) subset, death was not prevented in CD8(+)CD28(-) cells. These results suggest that CD8(+)CD28(-) T cells are more functionally differentiated than the CD8(+)CD28(+) subset and indicate they may represent a terminally differentiated effector population which is destined for clearance by apoptosis at the end of the immune response.

How to supervise a thesis: best practice

Adequate supervision of a research thesis is no simple matter. In this article, the requirements of both the supervisor and the student are considered, and essential recommendations are outlined.

IFN-alpha and IFN-beta: a link between immune memory and chronic inflammation

The majority of expanded T cells generated during an immune response are cleared by apoptosis. Prevention of death in some activated T cells enables the persistence of a memory T-cell pool. Here, observations that IFN-alpha and IFN-beta inhibit activated T-cell apoptosis are described. Although this enables memory T cells to persist without antigen, excessive IFN-alpha or IFN-gamma secretion might lead to chronic inflammation.

Serine/threonine protein kinases and apoptosis

Over the past decade, our understanding of apoptosis, or programmed cell death, has increased greatly, with the identification of some of the major components of the apoptotic programme and the processes regulating their activation. Although apoptosis is an intrinsic process present in all cells, it can be regulated by extrinsic factors, including hormones, growth factors, cell surface receptors, and cellular stress. The actions of both pro- and antiapoptotic factors are often affected by modulation of the phosphorylation status of key elements of the apoptotic process. This minireview will focus on the role of protein kinases in apoptosis. Apoptosis is a multistep process and protein kinases have been implicated both in the upstream induction phase of apoptosis and in the downstream execution stage, as the direct targets for caspases. Due to the space constraints of this review it is not possible to discuss all of the kinases involved in the apoptotic process and we have focused here on the role of the serine/threonine protein kinases. The kinases of this family that have been suggested to play a role in apoptosis are the mitogen-activated protein kinase (MAPK) family, specifically p42/44 ERK, p38 MAPK and c-Jun N-terminal kinase (JNK), cyclic AMP-dependent protein kinase (PKA), protein kinase B (PKB), or Akt and protein kinase C (PKC). We have also considered briefly the potential for the regulation of these kinases by tyrosine protein kinases, such as c-abl.

The small GTPase, Rap1, mediates CD31-induced integrin adhesion

Integrin-mediated leukocyte adhesion is a critical aspect of leukocyte function that is tightly regulated by diverse stimuli, including chemokines, antigen receptors, and adhesion receptors. How cellular signals from CD31 and other adhesion amplifiers are integrated with those from classical mitogenic stimuli to regulate leukocyte function remains poorly understood. Here, we show that the cytoplasmic tail of CD31, an important integrin adhesion amplifier, propagates signals that induce T cell adhesion via beta1 (VLA-4) and beta2 (LFA-1) integrins. We identify the small GTPase, Rap1, as a critical mediator of this effect. Importantly, CD31 selectively activated the small Ras-related GTPase, Rap1, but not Ras, R-Ras, or Rap2. An activated Rap1 mutant stimulated T lymphocyte adhesion to intercellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM), as did the Rap1 guanine nucleotide exchange factor C3G and a catalytically inactive mutant of RapGAP. Conversely, negative regulators of Rap1 signaling blocked CD31-dependent adhesion. These findings identify a novel important role for Rap1 in regulating ligand-induced cell adhesion and suggest that Rap1 may play a more general role in coordinating adhesion-dependent signals during leukocyte migration and extravasation. Our findings also suggest an alternative mechanism, distinct from interference with Ras-proximal signaling, by which Rap1 might mediate transformation reversion.

High cell density provides potent survival signals for resting T-cells

Activated T-cells are susceptible to apoptosis through two particularly important pathways: ligation of CD95 (Fas/Apo-1) or cytokine deprivation. Resting T-cells have until recently been considered to be relatively resistant to apoptosis. In this report we show that resting T-cells die rapidly by apoptosis when deprived of serum or cell contact. Primed CD45RO+ cells were more susceptible than naive CD45RA+ cells, consistent with their relative expression of Bcl-2. CD4+, CD8+ and gammadelta T-cells were equally prone to apoptosis under all studied conditions. A linear relationship between cell survival and serum concentration was observed for cells cultured between 0.5-2x10(6)/ml. T-cells cultured at low density died even in high concentrations of serum. However, resting T-cells cultured at high cell density (4x10(6)/ml) survived for extended periods in the absence of serum or other survival factors. This effect was mediated by the production of soluble factors and independent of integrin mediated signals. These results suggest that T-cells at sites of high density such as the lymph node paracortex are independent of external survival factors, while those trafficking through the peripheral circulation are highly dependent on serum derived factors for survival.

Regulation of apoptosis and replicative senescence in CD8+ T cells from patients with viral infections

Activated T lymphocytes are generated during an immune response. The induction of T lymphocyte proliferation is one way in which cell numbers can be controlled. However, once generated, the increased numbers of cells must be removed in order to re-establish cellular homoeostasis within the immune system. In this paper we describe how the numbers of activated T cells can be regulated by two distinct mechanisms, namely apoptosis and replicative senescence. In addition, we suggest that the regulation of cell clearance, as opposed to cell persistence, after an immune response is intimately involved in the generation of immune memory.

Mass spectrometric detection and identification of ortho, para-benzyltoluenes and oligotoluenes

Mass spectrometric detection and identification of ortho- and para-benzyltoluenes and oligotoluenes, C(21)-C(49), in several reaction mixtures was performed. Thus, the corresponding electron impact spectra were acquired and analyzed, this in addition to constant B/E linked scans and high-resolution data. Copyright 2000 John Wiley & Sons, Ltd.

Chemokine and chemokine receptor interactions provide a mechanism for selective T cell recruitment to specific liver compartments within hepatitis C-infected liver

The role played by chemokines in regulating the selective recruitment of lymphocytes to different tissue compartments in disease is poorly characterized. In hepatitis C infection, inflammation confined to portal areas is associated with a less aggressive course, whereas T cell infiltration of the liver parenchyma is associated with progressive liver injury and cirrhosis. We propose a mechanism to explain how lymphocytes are recruited to hepatic lobules during bursts of necroinflammatory activity in chronic hepatitis C infection. We report here that lymphocytes infiltrating hepatitis C-infected liver express high levels of the chemokine receptors CCR5 and CXCR3. However, whereas the CCR5 ligands macrophage inflammatory protein-1alpha and -1beta were largely confined to vessels within portal tracts, the CXCR3 ligands IFN-inducible protein-10 and monokine-induced by IFN-gamma were selectively up-regulated on sinusoidal endothelium. In vitro, human hepatic sinusoidal endothelial cells secreted IFN-inducible protein-10 and monokine-induced by IFN-gamma in response to stimulation with IFN-gamma in combination with either IL-1 or TNF-alpha. This suggests that intrahepatic Th1 cytokines drive the increased expression of IFN-inducible protein-10 and monokine-induced by IFN-gamma and thereby promote the continuing recruitment of CXCR3-expressing T cells into the hepatic lobule in chronic hepatitis C infection.

Contribution of bradykinin B(1) and B(2) receptors in allergen-induced bronchial hyperresponsiveness

Bradykinin (BK) is a peptide mediator generated at sites of inflammation and its effects are mediated through constitutively expressed B(2) receptor or through induction of B(1) receptors. We examined the role of these receptors in bronchial hyperresponsiveness (BHR). Brown-Norway rats sensitized with ovalbumin (OA) and Al(OH)(3) intraperitoneally, were exposed 3 wk later to either saline or OA aerosol. B(1) receptor antagonist desArg(10)[Hoe140] (200 nmol/kg or 1 micromol/kg, intraperitoneally) or B(2) receptor antagonist Hoe140 (200 nmol/kg, intraperitoneally) was administered 30 min before allergen exposure. Hoe140 had no effect on OA-induced BHR to acetylcholine (ACh) and bronchoalveolar lavage fluid (BALF) cellular profiles, but inhibited bronchoconstriction to BK (p < 0.04). At both doses, desArg(10)[Hoe140] dose-dependently inhibited allergen-induced BHR to ACh (p < 0.01), but had no effect on bronchoconstriction to BK or baseline ACh responsiveness. The inflammatory cells in BALF were not affected apart from reduced lymphocyte numbers at the highest dose. B(1) receptor mRNA expression measured by Northern analysis was increased after allergen exposure in sensitized lungs, with a peak at 2 to 6 h after exposure, whereas B(2) receptor mRNA expression remained unchanged. Newly induced BK B(1) receptors may be involved in allergen-induced BHR to ACh, whereas constitutive B(2) receptors mediate BK-induced bronchoconstriction.

Unreliability of carcinoembryonic antigen (CEA) reverse transcriptase-polymerase chain reaction (RT-PCR) in detecting contaminating breast cancer cells in peripheral blood stem cells due to induction of CEA by growth factors

RT-PCR is increasingly used for the detection of minimal residual disease in solid tumors. Carcinoembryonic antigen (CEA) RT-PCR seemed to be highly specific for detection of tumor cells when tested on PBMC. A very high frequency of RT-PCR amplification product for CEA in PBSC from breast cancer patients mobilized with G-CSF was found. However, this result contrasted with tumor cell detection by immunocytochemistry (ICC) which showed no correlation with RT-PCR results. In addition, CEA mRNA was amplified in most G-CSF-mobilized PBSC samples derived from patients with hematological malignancies and from healthy donors of allogeneic stem cells, although no circulating epithelial cells could be demonstrated by ICC. CEA RT-PCR expression was observed in PBMC from healthy individuals incubated in vitro with G-CSF. These data suggest that CEA transcription can be induced by G-CSF, resulting in a loss of specificity of CEA RT-PCR for tumor cell detection in PBMC. We conclude, CEA RT-PCR may not be recommended to detect tumor cell contamination in peripheral blood from patients treated with G-CSF. This may have implications on tumor cell detection by RT-PCR in tissues where endogenous or exogenous growth factors may induce the transcription of CEA or other genes.

Molecular analysis of resolving immune responses in uveitis

To identify the cellular immune processes underlying intra-ocular inflammation, aqueous humour was obtained at cataract surgery from 22 patients with clinically inactive uveitis and 24 patients with age-related cataract. mRNA expression for the cytokines IL-1beta, IL-2, IL-4, IL-6, IL-10, IL-12, interferon-gamma (IFN-gamma), transforming growth factor-beta (TGF-beta); T cell subsets CD3, CD4, CD8; monocytes and macrophages (CD14); and B cells (CD19) was measured using reverse transcriptase-polymerase chain reaction (RT-PCR) and radiometric analysis. The majority of uveitis patients demonstrated a T cell-mediated inflammatory response, predominately involving a Th1-like cytokine profile with expression of IL-2 and IFN-gamma in 16/22 and 18/22 samples, respectively. These cytokines were present in only a small number of patients with age-related cataract. This Th1-like polarization was supported by an increased expression of CD8 in a number of patients. IL-1beta was expressed in only six uveitic eyes. Only four patients expressed either IL-4 or IL-10 and no patient expressed both. TGF-beta mRNA could be detected in 18/22 uveitis patients and 15/24 controls. IL-12, the paradigmatic Th1-inducing cytokine, was absent in all samples but CD14 was expressed in the majority of patients and controls. CD19 could not be detected in any sample. The cellular infiltrate in the uveitic eyes showed clear evidence of low IL-1 and absent IL-12 expression despite a Th1-like profile and high expression of macrophages. This strongly suggests that the systemic immunosuppressive therapy used prior to surgery in some patients and/or the chronicity of the uveitis had actively suppressed/switched off macrophage function, leading to resolution of T cell activity.

Repeated allergen exposure of sensitized Brown-Norway rats induces airway cell DNA synthesis and remodelling

Chronic inflammation in asthmatic airways can lead to characteristic airway smooth muscle (ASM) thickening and pathological changes within the airway wall. This study assessed the effect of repeated allergen exposure on ASM and epithelial cell deoxyribonucleic acid (DNA) synthesis, cell recruitment and airway wall pathology. Brown-Norway rats were sensitized and then exposed to ovalbumin or saline aerosol every 3 days on six occasions. After the final exposure, rats were administered twice daily for 7 days with the DNA S-phase marker bromodeoxyuridine (BrdU). Using a triple immunohistochemical staining technique, BrdU incorporation into ASM and epithelium was quantified employing computer-assisted image analysis. There were >3-fold mean increases in BrdU incorporation into ASM from 1.3% of cells (95% confidence interval (CI) 1.0-1.6) in saline controls to 4.7% (95% CI 2.6-6.7) after allergen exposure (p<0.001), and in airway epithelium, from 1.3 (95% CI 0.6-2.0) BrdU-positive cells x mm basement membrane(-1) in saline controls to 4.9 (95% CI 3.0-6.7) after allergen exposure (p<0.001). There was increased subepithelial collagen deposition and mucus secretion along with a significant eosinophil and lymphocyte recruitment to the airways. Increased rates of deoxyribonucleic acid synthesis in both airway smooth muscle and epithelial cells along with changes to the airway wall pathology may precede the establishment of smooth muscle thickening and airway remodelling after repeated allergen exposure in rats. This model seems to be appropriate for studying structural changes within the airways as observed in asthma.

SB 203580, an inhibitor of p38 mitogen-activated protein kinase, enhances constitutive apoptosis of cytokine-deprived human eosinophils

The role of p38 mitogen-activated protein (MAP) kinase, and extracellular-regulated protein kinase -1 and -2 in regulating constitutive apoptosis and interleukin (IL)-5-induced survival of human eosinophils have been investigated. Two populations of donors were identified whose eosinophils, in the absence of exogenous cytokines, underwent apoptosis at different rates. Eosinophils were thus arbitrarily classified as either "fast"- or "slow"-dying cells, where greater or less than 15% of the cells were apoptotic at 2 days, respectively. The selective p38 MAP kinase inhibitor, SB 203580, increased constitutive eosinophil apoptosis in both populations (EC(50) approximately 2 microM) as evinced from morphological analysis, flow cytometry, and DNA laddering. The ability of SB 203580 to kill eosinophils was not due to nonspecific toxicity or through the inhibition of prostanoid or leukotriene production. Exposure of eosinophils to IL-5, at a concentration (10 pM) that enhanced survival maximally, abolished SB 203580-induced apoptosis. In contrast PD 098059, which selectively blocks MAP kinase kinase (MEK) 1, did not affect apoptosis of fast- or slow-dying eosinophils, or the enhanced survival of cells effected by IL-5. Collectively, these results suggest that: 1) the basal activity of p38 MAP kinase may regulate the survival of cytokine-deprived eosinophils through inhibition of apoptosis, 2) the enhancement of eosinophil survival effected by IL-5 is mediated by a mechanism(s) divorced from the activation of p38 MAP kinase, and 3) neither spontaneous eosinophil apoptosis nor their enhanced survival by IL-5 involves the activation of MEK-1.

Inhibition of T cell apoptosis by IFN-beta rapidly reverses nuclear translocation of protein kinase C-delta

Type I interferons rescue activated human T cells from cytokine deprivation-induced apoptosis. Our data now show that IFN-beta also rapidly inhibits apoptotic signals induced through the Fas receptor (CD95) in human T cells. To identify upstream signaling elements that could be targets of IFN-beta, we have studied protein kinase C (PKC). PKC-delta is actively involved in the regulation of apoptosis and immunofluorescence staining revealed that early in apoptosis PKC-delta accumulated in the nucleus. Addition of IFN-beta to T cells already deprived of survival factors or treated with anti-Fas antibody caused a rapid retranslocation of PKC-delta away from the nucleus. Furthermore, the generation of a constitutively active catalytic fragment by cleavage of PKC-delta by caspase 3 occurred only after translocation of full-length PKC-delta to the nucleus. IFN-beta also inhibited caspase 3 and the proteolytic activation of PKC-delta. We conclude from these studies that nuclear translocation of PKC-delta is an early event in T cell apoptosis and that IFN-beta rapidly reverses this process.

Cysteinyl-leukotrienes partly mediate eotaxin-induced bronchial hyperresponsiveness and eosinophilia in IL-5 transgenic mice

Eotaxin, a selective chemoattractant for eosinophils, induces lung eosinophilia and bronchial hyperresponsiveness (BHR) when administered intratracheally to interleukin-5 (IL-5) transgenic mice. We determined whether these effects of eotaxin were mediated through the production of cysteinyl-leukotrienes. IL-5 transgenic mice were administered eotaxin (5 micrograms) intratracheally after pretreatment with either diluent or a selective 5-lipoxygenase inhibitor SB210661 or a cysteinyl-leukotriene receptor antagonist, pranlukast. Twenty-four hours later, bronchial responsiveness to acetylcholine was measured and the degree of eosinophil influx was determined in bronchoalveolar lavage fluid (BALF) or in lung tissue. Both pranlukast and SB210661 significantly attenuated BHR induced by eotaxin with logPC(50), which is the concentration of acetylcholine needed to increase baseline insufflation pressure by 50%, from -0.43 +/- 0.16 to 0.39 +/- 0.10 and from -0.22 +/- 0.10 to 0.53 +/- 0.10, respectively (p < 0.05). There was also a significant attenuation of the eosinophil counts in BALF and in airways. BALF levels of leukotriene C(4) (LTC(4)) showed a significant increase after eotaxin from 23.9 +/- 6.7 to 165.0 +/- 35.0 pg/ml (p < 0.05) but were partially suppressed by both SB210661 (71.2 +/- 21.0) and pranlukast (62.7 +/- 11.5). Concentrations of LTB(4) were not significantly changed. We conclude that eotaxin-induced effects in the airways of IL-5 transgenic mice are partly mediated by the activation of 5-lipoxygenase enzyme leading to the generation of cysteinyl-leukotrienes.

Inhibition of ozone-induced lung neutrophilia and nuclear factor-kappaB binding activity by vitamin A in rat

Vitamin A binds to retinoic acid receptors, which in turn may interact with other transcription factors. We determined its effect (2500 and 5000 IU/kg) on nuclear factor-kappaB binding activity in the lung, airway inflammation and bronchial hyperresponsiveness in rats exposed to ozone. Ozone (3 ppm, 3 h) caused neutrophil influx into bronchoalveolar lavage fluid (16.2+/-0.8 x 10(5) cells/ml, p < 0.01) and bronchial hyperresponsiveness (-logPC200ACh = 2.54+/-0.19, p < 0.05, compared to control animals, respectively). Vitamin A inhibited this neutrophilia dose-dependently together with the increased DNA-binding activity of nuclear factor-KB in lung extracts. Vitamin A did not affect bronchial hyperresponsiveness at both doses. Vitamin A inhibits ozone-induced neutrophilic inflammation through a reduction in nuclear factor-kappaB DNA binding activity.

Homophilic PECAM-1(CD31) interactions prevent endothelial cell apoptosis but do not support cell spreading or migration

PECAM-1 (CD31) is a highly abundant cell surface glycoprotein expressed on haemopoietic and endothelial cells. As well as mediating homophilic (PECAM-1/PECAM-1) adhesion, PECAM-1 can also bind the integrin alphavbeta3. Both PECAM-1 and alphavbeta3 have been shown to have roles in regulating angiogenesis, endothelial tube formation and in the case of alphavbeta3, endothelial cell apoptosis. In this study we show that despite being expressed at equivalent levels, endothelial alphavbeta3 is not a ligand for PECAM-1. Rather, PECAM-1 supports homophilic binding on HUVEC with similar characteristics to those we have previously reported for leukocytes and becomes tyrosine phosphorylated after homophilic PECAM-1 and integrin/fibronectin engagement. Immunoprecipitation studies show that in addition to SHP-2, tyrosine phosphorylated PECAM-1 can interact with at least four other phosphoproteins in pervanadate stimulated HUVEC. While PECAM-1/PECAM-1 interactions support robust endothelial cell adhesion, they do not support cell spreading or migration. In addition PECAM-1 homophilic adhesion rescues HUVEC from serum deprivation-induced apoptosis. Taken together our results indicate that PECAM-1 homophilic interactions play an important role in interendothelial cell adhesion, survival and signalling.

Quantitative flow cytometry for the analysis of T cell receptor Vbeta chain expression

Detailed characterisation of the T cell receptor (TCR) repertoire expressed by peripheral blood lymphocytes has been used to study specific T cell responses in disease conditions. The methods have mostly involved molecular biology analysis of transcribed gene products isolated from T cell subsets or individual clones. Extensive characterisation of the TCR Vbeta chain repertoire by flow cytometry is now possible due to the recently increased availability of specific monoclonal antibodies. However, there are major logistical problems inherent in this analysis relating to the number of cells required to obtain accurate results and the vast amounts of data generated. To reduce these factors to a practical level, we have performed a detailed study to define the limits of precision of cell subset analysis by flow cytometry. Maximal achievable precision was obtained by analysing 10(4) lymphocytes; no significant improvement was obtained by analysing greater numbers of cells up to 10(5) cells, even for cell subsets present at frequencies as low as 0.5%. Careful application of these precision profiles will also permit more effective use of clinical research samples for flow cytometry when the availability of cells is limited.

alpha4 integrin-dependent eotaxin induction of bronchial hyperresponsiveness and eosinophil migration in interleukin-5 transgenic mice

We investigated the roles of eosinophil infiltration and activation induced by the eosinophil-selective chemokine eotaxin, and of the expression of eosinophil alpha4 and beta2 integrins in causing bronchial hyperresponsiveness (BHR) in interleukin (IL)-5 CBA/Ca transgenic mice. These mice did not show BHR, despite the presence of some eosinophils in the lungs. Intratracheal mouse recombinant eotaxin (3 micrograms) did not induce BHR in wild-type mice. In IL-5 transgenic mice, eotaxin (3 and 5 micrograms) increased responsiveness at 24 h and increased eosinophils in bronchoalveolar lavage (BAL) fluid by 9.4- and 14-fold by 24 h, respectively, together with augmentation of eosinophil peroxidase activity and eosinophil infiltration in the airway submucosa. Using flow cytometry, the expression of alpha4, CD11b, and CD18 was upregulated in BAL, but not in blood, eosinophils. A rat anti-alpha4 antibody inhibited eotaxin-induced BHR and eosinophil migration and activation, but an anti-CD11b antibody had no significant effects on BHR. A combination of both antibodies was more effective. IL-5 and eotaxin synergize in the induction of BHR and airway eosinophilia, effects that are dependent on the induction of eosinophil alpha4 integrin. Expression of BHR depends on the recruitment and activation of eosinophils.