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Biomedical subjects

J Savill

Publications and source records attributed to J Savill.

At least 55 records · Page 3Linked to original sources
PubMed1996

Identification of a domain (155-183) on CD36 implicated in the phagocytosis of apoptotic neutrophils.

Clearance of apoptotic neutrophils by macrophages is a crucial event following the resolution of acute inflammation. CD36, together with alphavbeta3, has been identified as one of the adhesion molecules on the surface of macrophages implicated in the clearance of polymorphonuclear leukocytes. The domain on CD36 implicated in the phagocytosis of aged neutrophils remains to be elucidated. In this study, COS cells transfected with human CD36 cDNA had a significantly higher capacity to phagocytose human apoptotic neutrophils compared with murine CD36 cDNA. Moreover, monoclonal antibodies 10/5 or OKM5 (epitopes identified on amino acids 155-183) but not monoclonal antibody 13/10 (epitope identified on amino acids 30-76) inhibited phagocytosis of apoptotic neutrophils by COS cells transfected by human CD36. Swapping the human CD36 155-183 domain from human to murine CD36 (human-murine CD36 chimera) imparted to murine CD36-transfected COS cells an increased capacity to phagocytose apoptotic neutrophils. Conversely, when the murine domain 155-183 was inserted in human CD36, a decreased phagocytic capacity was observed. In addition, a synthetic peptide(155-169) but not its scrambled form significantly inhibited phagocytosis. These results identify for the first time a functional domain encompassing amino acids 155-183 on human CD36 implicated in the recognition and phagocytosis of apoptotic neutrophils.

Animals↗
PubMed1996

Expression of the multifunctional extracellular matrix protein thrombospondin in crescentic glomerulonephritis.

Thrombospondin is a multifunctional 450 kD glycoprotein which may be secreted into the extracellular matrix by a wide variety of cells. Occasional foci of immunoreactive thrombospondin have previously been demonstrated within normal human glomeruli. A specific polyclonal antibody directed against thrombospondin 1 was used to examine the distribution of this regulatory glycoprotein in renal biopsies from patients with a variety of renal diseases, including rapidly progressive glomerulonephritis associated with circulating antibodies to neutrophils, active or quiescent systemic lupus erythematosus, and membranous nephropathy, together with normal renal tissue. The results demonstrated the marked up-regulation of thrombospondin expression in acutely inflamed renal tissue with strongly positive, predominantly extracellular staining of glomerular crescents, although cytoplasmic staining of epithelial cells was also seen, indicating that these cells may contribute to thrombospondin accumulation at these sites. Occasional segmental mesangial staining was seen in cases of active lupus and rapidly progressive glomerulonephritis, while some focal interstitial staining around peritubular capillaries was seen in all renal tissue examined. These results suggest that thrombospondin may play an important role in the regulation of cellular recruitment, proliferation, and function in crescentic glomerulonephritis.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed1996

Relationship between granulocyte activation, pulmonary granulocyte kinetics and alveolar permeability in extrapulmonary inflammatory disease.

1. The aim of the study was to examine the relationship between granulocyte activation, pulmonary intravascular granulocyte transit, pulmonary extravascular granulocyte migration and lung injury in patients with systemic conditions (bone marrow transplant recipients, inflammatory bowel disease and systemic vasculitis) in which abnormalities of pulmonary granulocyte traffic have previously been reported. 2. A double 111In-99mTc granulocyte labelling technique was used for quantification of granulocyte kinetics in 23 patients, of whom five were control patients. The pulmonary vascular granulocyte pool was measured from dynamic data centred on the 99mTc signal and expressed as a percentage of the total blood granulocyte pool. Granulocyte migration was quantified on 24 h images using the 111In signal. Granulocyte activation was measured as the percentage of cells showing a change in shape. The clearance rate of an inhaled aerosol of 99mTc-diethylenetriaminepenta-acetic acid (DTPA) was used as a marker of lung injury. 3. Pulmonary granulocyte pool, migration, activation and aerosol clearance, although highly variable in the patient groups, were, in general, elevated compared with the controls. 4. Granulocyte activation correlated with pulmonary granulocyte pool (Rs = 0.72, n = 22, P < 0.01), while the t1/2 of DTPA clearance correlated with migration (Rs = -0.84, n = 17, P < 0.01). Fifteen patients had an expanded pulmonary granulocyte pool, of whom six with no evidence of migration, had a normal DTPA clearance, while nine, who had an abnormal migration signal, had an accelerated DTPA clearance. The pulmonary granulocyte pool in these nine was significantly higher than in the six without a migration signal. 5. Activation of granulocytes results in delayed transit through the lung vasculature. With increasing margination, granulocytes migrate into the lung interstitium and injure the lung. An increased intravascular pool does not by itself lead to lung injury.

Adult↗
PubMed1996

What role does apoptosis play in progression of renal disease?

Apoptosis (programmed cell death) is now recognized to play an important role in regulating the number of renal cells in health and disease. Apoptosis may mediate beneficial deletion both of leukocytes and of excess resident cells from the inflamed glomerulus. However, this review focuses on the growing evidence that inappropriate engagement of the cell death 'program' contributes to the progression of renal diseases such as polycystic kidney disease and glomerulonephritis, mediating the loss of 'desirable' cells and eventual development of the hypocellular end-stage kidney.

Animals↗
PubMed1996

Human monocyte-derived macrophage phagocytosis of senescent eosinophils undergoing apoptosis. Mediation by alpha v beta 3/CD36/thrombospondin recognition mechanism and lack of phlogistic response.

Eosinophils may mediate tissue injury in a number of allergic diseases. Previously, we reported that eosinophils constitutively undergo apoptosis (programmed cell death) in culture. As this led to phagocytosis of the intact senescent cell by macrophages, we proposed that apoptosis represented an injury-limiting eosinophil disposal mechanism. Ingestion of apoptotic neutrophils by human monocyte-derived macrophages (M phi s) was found to be mediated by adhesive interactions between thrombospondin and the M phi alpha v beta 3 vitronectin receptor integrin and M phi CD36. As this failed to elicit a pro-inflammatory response from M phi s, we sought evidence that this specific, nonphlogistic clearance mechanism may operate in eosinophil disposal. In this study, we found that M phi ingestion of apoptotic eosinophils was specifically inhibited by monoclonal antibodies to M phi alpha v beta 3, CD36, and thrombospondin and by other inhibitors of this recognition mechanism including RGD peptide and amino sugars. Furthermore, not only did M phi ingestion of intact apoptotic eosinophils fail to stimulate release of the phlogistic eicosanoid thromboxane, but there was also a lack of increased release of the pro-inflammatory cytokine granulocyte/macrophage colony-stimulating factor. However, increased release of these mediators was observed when M phi s took up senescent post-apoptotic eosinophils that had been cultured long enough to lose plasma membrane integrity. The data indicate that the nonphlogistic alpha v beta 3/CD36/thrombospondin macrophage recognition mechanism is available for clearance of intact senescent eosinophils undergoing apoptosis. Furthermore, our findings suggest that, by contrast, phagocytosis of post-apoptotic eosinophils may elicit undesirable pro-inflammatory responses.

Amino Sugars↗
PubMed1995

Early detection of canine ceroid-lipofuscinosis (CCL): an ultrastructural study.

English setters from the Koppang line have been used as a model for the juvenile type of Batten disease in human patients. This disorder, canine ceroid-lipofuscinosis (CCL), has been shown by Koppang [1973: Mech Ageing Dev 2:421-445] to be an autosomal recessive disorder. Homozygous animals show the typical storage granules by autofluorescence; however, the autofluorescence material cannot easily be detected in affected dogs before age 3-6 months. At the present time the early stages of CCL can be studied only in litters from homozygous matings. Electron microscopy was used to study the reliability of diagnosing affected animals in heterozygous-heterozygous (HET-HET) and heterozygous-homozygous (HET-HOM) litters at age 2-3 weeks. The electron micrographs of brain biopsies were examined and the number of all dense bodies (d.b.), including linear and fingerprint patterns typical of CCL, were counted per neuron. The results indicated that affected animals have higher numbers of dense bodies than nonaffected carriers. Four-6 months later confirmatory diagnoses were made on a second contralateral biopsy taken and examined as a frozen section by autofluorescence. The diagnoses made by electron microscopy at age 2-3 weeks appeared identical to the results obtained by autofluorescence at 4-6 months of age.

Animals↗
PubMed1995

CD36 gene transfer confers capacity for phagocytosis of cells undergoing apoptosis.

Phagocyte recognition and ingestion of intact cells undergoing apoptosis are key events in this generally important program of cell death. Insufficient phagocyte capacity for apoptotic cells can result in failure to clear dying cells before membrane integrity is lost, resulting in leakage of noxious cell contents and severe tissue damage. However, no means has been available to increase phagocytic clearance of apoptotic cells. We now report that transfection of the macrophage adhesion molecule CD36 into human Bowes melanoma cells specifically conferred greatly increased capacity to ingest apoptotic neutrophils, lymphocytes, and fibroblasts, comparable to that exhibited by macrophages. Furthermore, when CD36 was transfected into another cell type with limited capacity to take up apoptotic bodies, the monkey COS-7 cell, similar effects were observed. Therefore, CD36 gene transfer can confer "professional" capacity to ingest apoptotic cells upon "amateur" phagocytes.

Animals↗
PubMed1995

Proinflammatory cytokines potentiate thrombospondin-mediated phagocytosis of neutrophils undergoing apoptosis.

Apoptosis leads to swift recognition, ingestion, and degradation of intact senescent neutrophils by macrophages. This protects tissues from leakage of noxious contents from dying cells and may promote resolution of inflammation. However, little has been known of the mechanisms that regulate macrophage capacity for apoptotic cells during an inflammatory response. We examined whether proinflammatory cytokines modulated phagocytosis of senescent neutrophils undergoing apoptosis by human monocyte-derived macrophages at 4 days maturity (4d M phi), an in vitro model of neutrophil "disposal" by apoptosis. Pretreatment of 4d M phi with granulocyte-macrophage-CSF increased the proportion of 4d M phi taking up apoptotic PMN in a concentration-dependent fashion by up to approximately 240%. This was by a rapid effect detectable by 4 h and exerted on the M phi, not the PMN. Granulocyte-macrophage-CSF also increased the number of apoptotic PMN taken up by each M phi. IFN-gamma, IL-1 beta, TNF-alpha, and TGF-beta 1 also enhanced phagocytosis, but IL-4 and IL-6 had no effect. In each case, the cytokine-expanded phagocytic subpopulation employed the thrombospondin (TSP)-dependent recognition mechanism defined for mature M phi, in which M phi vitronectin receptor and CD36 cooperate. However, commensurate increases in M phi expression of VnR, TSP, or CD36 were not detectable, indicating that TSP-mediated recognition can be recruited by other mechanisms. Cytokines did not recruit phosphatidylserine-dependent recognition, the other major mechanism by which some macrophage populations ingest apoptotic cells. Thus, M phi phagocytosis of apoptotic neutrophils can be potentiated by proinflammatory cytokines, suggesting a mechanism for negative feedback control of neutrophil number at inflamed sites.

Apoptosis↗
PubMed1995

Granulocyte clearance by apoptosis in the resolution of inflammation.

It has recently been recognized that extravasated granulocytes undergo apoptosis or programmed cell death. This process controls the functional longevity of these cells and is exquisitely modulated by environmental inflammatory mediators. By contrast with necrosis, an alternative fate for granulocytes in tissues, during apoptosis the granulocyte membrane remains intact and potentially injurious granule contents are retained. The intact apoptotic cell is removed by macrophages utilizing novel surface recognition mechanisms which fail to trigger a pro-inflammatory macrophage response. The balance between granulocyte apoptosis and necrosis in inflamed tissues may be an important determinant of the degree of tissue injury, and further dissection of the mechanisms of granulocyte apoptosis and removal may lead to new therapeutic strategies in inflammatory disease.

Animals↗
PubMed1995

Apoptosis and renal injury.

Apoptosis or programmed cell death is a major focus of interest in many fields of research. Recent advances include definition of key molecules driving the cell death programme, including Fas and Fas-ligand in the plasma membrane, and cytoplasmic proteases such as interleukin-1 beta-converting enzyme. These are kept in check by 'survival' signals conferred by exogenous cytokines and the extracellular matrix, or by endogenous proteins encoded by the bcl-2 gene family. Important insights into the programme of mammalian cell death have come from comparative biology. The scene is now set for study of apoptosis in renal health and disease, in which recent studies indicate key roles in remodelling of both glomeruli and tubules after renal injury.

Acute Kidney Injury↗
PubMed1994

The specific recognition by macrophages of CD8+,CD45RO+ T cells undergoing apoptosis: a mechanism for T cell clearance during resolution of viral infections.

During viral infections, CD8+,CD45RO+ T populations expand. These primed cells express abundant levels of cytoplasmic granules that contain perforin and TIA-1. Recent work has suggested that the majority of this CD8+ population downregulates Bcl-2 protein expression and is destined to undergo apoptosis. In this study we have investigated the elimination of these apoptotic CD8+ T cells by both human monocyte-derived and murine bone marrow macrophages. We have found that these phagocytes recognize and ingest both apoptotic CD8+ and CD4+ T cells using an alpha v beta 3 (vitronectin receptor)/CD36/thrombospondin recognition system, with the same receptors being used in the recognition of apoptotic neutrophils. These data provide new evidence for a mechanism that enables the clearance of greatly increased populations of CD8+ effector cells which are found during viral infections. This enables cellular homeostasis to occur in the host upon resolution of viral diseases in vivo.

Amino Acid Sequence↗