Biomedical subjects

G A Bishop

Publications and source records attributed to G A Bishop.

At least 19 recordsLinked to original sources

PubMed2002

Cord blood mononuclear cell cytokine responses in relation to maternal house dust mite allergen exposure.

BACKGROUND: Cord blood mononuclear cells have demonstrated specific immune responses to environmental allergens. OBJECTIVE: To establish whether the nature of this response is related to the level of maternal antenatal exposure to house dust mite (HDM) allergen and, hence, whether antenatal allergen avoidance may have a role in the prevention of allergic sensitization in children. METHODS: Children with a family history of asthma were recruited antenatally as subjects in a randomised controlled trial: the Childhood Asthma Prevention Study. HDM allergen (Der p 1) concentrations were measured in dust collected from the maternal bed at 36 weeks gestation. Cord blood mononuclear cells were stimulated in culture, separately, with phytohaemaglutinin (PHA) and HDM extract. Cytokine IL-4, IL-5, IL-10 and IFN-gamma concentrations in supernatant were measured by ELISA. mRNA signals for these cytokines were measured using RT-PCR. RESULTS: The median concentration of HDM allergen was 18.4 microg/g (interquartile range 7.3-35.3 microg/g). Median concentrations of IL-4, IL-5, IL-10 and IFN-gamma, after PHA stimulation were 4, 19, 401 and 1781 pg/mL, respectively. After HDM allergen stimulation the median concentrations were 0, 0, 20 and 14 pg/mL, respectively. The distribution of mRNA cytokine signals was similar. Neither cytokine protein concentrations nor cytokine mRNA signal levels were correlated with the concentration of HDM allergen in the mothers' beds at 36 weeks gestation. CONCLUSION: These findings do not support the view that the prevention of allergic disease in children requires the institution of HDM avoidance interventions during pregnancy.

Air Pollution, Indoor↗

PubMed2001

Multiple carboxyl-terminal regions of the EBV oncoprotein, latent membrane protein 1, cooperatively regulate signaling to B lymphocytes via TNF receptor-associated factor (TRAF)-dependent and TRAF-independent mechanisms.

Latent membrane protein 1 (LMP1) is an EBV-encoded transforming protein that strongly mimics the B cell-activating properties of a normal cellular membrane protein, CD40. LMP1 and CD40 both associate with the cytoplasmic adapter proteins called TNFR-associated factors (TRAFs). TRAFs 1, 2, and 3 bind to a region of LMP1 that is essential for EBV to transform B lymphocytes, carboxyl-terminal activating region (CTAR) 1. However, studies of transiently overexpressed LMP1 molecules, primarily in epithelial cells, indicated that a second region, CTAR2, is largely responsible for LMP1-mediated activation of NF-kappaB and c-Jun N-terminal kinase. To better understand LMP1 signaling in B lymphocytes, we performed a structure-function analysis of the LMP1 C-terminal cytoplasmic domain stably expressed in B cell lines. Our results demonstrate that LMP1-stimulated Ig production, surface molecule up-regulation, and NF-kappaB and c-Jun N-terminal kinase activation require both CTAR1 and CTAR2, and that these two regions may interact to mediate LMP1 signaling. Furthermore, we find that the function of CTAR1, but not CTAR2, correlates with TRAF binding and present evidence that as yet unidentified cytoplasmic proteins may associate with LMP1 to mediate some of its signaling activities.

Animals↗

PubMed2001

Snowmobile contributions to mobile source emissions in Yellowstone National Park.

Increases in the number of winter visitors to Yellowstone National Park during the past decade have raised concerns over the environmental impacts of snowmobiling in the park. During the 1998-99 season, more than 62,000 snowmobile and 1300 snow coach trips entered the park. Using the University of Denver's vehicle exhaust remote-sensing equipment, 1385 measurements of carbon monoxide (CO) and hydrocarbon (HC) emissions were collected from in-use snowmobiles at the west and south entrances to the park. Overall means of 392 +/- 4 g CO and 237 +/- 1 g HC were observed per kilogram of fuel consumed. In addition, using an ultraviolet monochromator, 460 measurements of toluene emissions were collected with a mean of 39 +/- 1 g toluene/kg of fuel. Using these data, a mobile source emissions inventory based on fuel use for Yellowstone National Park shows that snowmobiles account for 27% of the annual emissions of carbon monoxide and 77% of annual emissions of hydrocarbons using an equivalent best estimate for the summer mobile source emissions. Use of oxygenated fuels in snowmobiles was found to reduce CO emissions by 13.2 +/- 6.5% without an observed effect on HC emissions. Liquid-cooled sleds were found to have HC emissions 9.5 +/- 2.2% higher than those from fan-cooled sleds because of the increased intake and exhaust port sizes required in the larger liquid-cooled engines, which increases blowby in the 2-stroke engines.

Air Pollutants↗

PubMed2001

A short course of methylprednisolone immunosuppression inhibits both rejection and spontaneous acceptance of rat liver allografts.

BACKGROUND: The effects of immunosuppressive drugs on transplant tolerance have not been extensively studied, although their effect on rejection is well established. METHODS: We examined the effects of a short course of treatment with the immunosuppressive drug methylprednisolone (MP) on the survival of PVG liver allografts in Dark Agouti (DA) recipients that accepted the livers and in Lewis recipients that rejected the livers. Infiltration of liver allografts was examined by immunohistochemical staining of liver sections, and apoptosis was measured by terminal deoxynucleotide transferase-mediated dUTP nick end labeling. RESULTS: A 5-day course of MP (days 0 to 4) led to rejection of four of six livers (mean survival time [MST] 99 days) in DA recipients compared with long-term survival (MST >100 days) in untreated animals. Delayed administration of MP (days 3 to 7) exacerbated rejection in DA recipients, and all eight animals rejected the graft (MST 68.5 days). Treatment of Lewis recipients with MP did not significantly prolong survival when administered from days 0 to 4 (MST 13 days), although delay of administration improved the outcome. Treatment from days 3 to 7 resulted in an MST of 21 days, whereas treatment from days 7 to 11 resulted in an MST of 41.5 days. MP treatment from day 3 to day 7 reduced T cells and interleukin 2 receptor-expressing cells but increased the numbers of apoptotic cells infiltrating both DA and Lewis strain allografts. CONCLUSIONS: These results show that immunosuppression with MP inhibits both spontaneous tolerance and rejection of liver allografts in a rat model and question the efficacy of administering MP to all liver allograft recipients from the time of transplantation.

Animals↗

PubMed2001

Signaling through MHC class II molecules blocks CD95-induced apoptosis.

B cells are induced to express CD95 upon interaction with T cells. This interaction renders the B cells sensitive to CD95-mediated apoptosis, but ligation of proviability surface receptors is able to inhibit apoptosis induction. MHC class II is a key molecule required for Ag presentation to Th cells, productive T cell-B cell interaction, and B cell activation. We demonstrate here for the first time that MHC class II ligation also confers a rapid resistance to CD95-induced apoptosis, an affect that does not require de novo protein synthesis. Signaling through class II molecules blocks the activation of caspase 8, but does not affect the association of CD95 and Fas-associated death domain-containing protein. MHC class II ligation thus blocks proximal signaling events in the CD95-mediated apoptotic pathway.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Differential signaling and tumor necrosis factor receptor-associated factor (TRAF) degradation mediated by CD40 and the Epstein-Barr virus oncoprotein latent membrane protein 1 (LMP1).

Latent membrane protein 1 (LMP1) plays a critical role in B cell transformation by Epstein-Barr virus (EBV) and appears to mimic a constitutively active CD40 receptor. Intracellular tumor necrosis factor (TNF) receptor-associated factor (TRAF) adapter proteins, shown to contribute to signaling by both CD40 and LMP1, were recruited by both molecules to lipid-enriched membrane rafts. However, we found that TRAFs 2 and 3 were subsequently degraded after CD40- but not LMP1-induced signaling. This degradation was proteasome-dependent and required direct TRAF binding by CD40. Using a model system designed to directly compare the signaling potency of the cytoplasmic domains of LMP1 and CD40 in B lymphocytes, we found that LMP1 more potently activates c-Jun kinase and nuclear factor kappaB and induces higher levels of several B cell effector functions than does CD40. This suggests that LMP1 utilizes a modified CD40 signaling pathway. Failure to regulate TRAFs may contribute to the enhanced capacity of LMP1 to activate B cells as well as promote B cell transformation.

Animals↗

PubMed2001

The effects of altitude on heavy-duty diesel truck on-road emissions.

On-road measurements of carbon monoxide, hydrocarbons, and nitric oxide from 5772 heavy-duty diesel trucks at five locations in the United States and Europe show slightly increasing emissions with increasing altitude. The result for nitric oxide showed a statistically significant increase of 4.1 +/- 1 gNO/kg of fuel consumed/km increase in altitude. The increases for CO and HC were also statistically significant.

Air Pollutants↗

PubMed2001

Posttransplant administration of donor leukocytes induces long-term acceptance of kidney or liver transplants by an activation-associated immune mechanism.

Donor leukocytes play a dual role in rejection and acceptance of transplanted organs. They provide the major stimulus for rejection, and their removal from the transplanted organ prolongs its survival. Paradoxically, administration of donor leukocytes also prolongs allograft survival provided that they are administered 1 wk or more before transplantation. Here we show that administration of donor leukocytes immediately after transplantation induced long-term acceptance of completely MHC-mismatched rat kidney or liver transplants. The majority of long-term recipients of kidney transplants were tolerant of donor-strain skin grafts. Acceptance was associated with early activation of recipient T cells in the spleen, demonstrated by a rapid increase in IL-2 and IFN-gamma at that site followed by an early diffuse infiltrate of activated T cells and apoptosis within the tolerant grafts. In contrast, IL-2 and IFN-gamma mRNA were not increased in the spleens of rejecting animals, and the diffuse infiltrate of activated T cells appeared later but resulted in rapid graft destruction. These results define a mechanism of allograft acceptance induced by donor leukocytes that is associated with activation-induced cell death of recipient T cells. They demonstrate for the first time that posttransplant administration of donor leukocytes leads to organ allograft tolerance across a complete MHC class I plus class II barrier, a finding with direct clinical application.

Animals↗

PubMed2001

The immune response modifier resiquimod mimics CD40-induced B cell activation.

Members of the imidazoquinoline molecule family, including imiquimod and resiquimod (R-848), have potent antiviral and antitumor activities. Imiquimod cream (5%) (Aldara) is currently indicated for treatment of external genital and perianal warts. Previous characterization of these compounds has focused upon their ability to activate monocytes and dendritic cells, but recent studies have shown that resiquimod also stimulates B lymphocytes to proliferate and express an activated phenotype. This suggests that resiquimod could potentially serve as an effective vaccine adjuvant in stimulating a humoral immune response. This study shows that resiquimod mimics effects of the T-dependent CD40 signal in both mouse and human B cell lines. Resiquimod, like CD40, stimulates antibody secretion, cytokine production, protection from apoptosis, and CD80 upregulation. In addition, it shows synergy with signals delivered by the B cell antigen receptor and heightens CD40-mediated B cell activation, demonstrating that resiquimod can enhance antigen-specific responses in B lymphocytes.

Adjuvants, Immunologic↗

PubMed2001

B lymphocyte activation by contact-mediated interactions with T lymphocytes.

T cell dependent B lymphocyte activation requires interactions between numerous receptor-ligand pairs on the two cell types. Recently, advances have been made both in understanding how these various signals regulate B cell effector functions and in identifying many new receptor-ligand pairs that contribute to the regulation of B cell function by T lymphocytes.

Animals↗

PubMed2001

Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) for measurement of cytokine and growth factor mRNA expression with fluorogenic probes or SYBR Green I.

Real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) is the method of choice for rapid and reproducible measurements of cytokine or growth factor expression in small samples. Fluorescence detection methods for monitoring real-time PCR include fluorogenic probes labelled with reporter and quencher dyes, such as Taqman probes or Molecular Beacons and the dsDNA-binding dye SYBR Green I. Fluorogenic (Taqman) probes for a range of human and rat cytokines and growth factors were tested for sensitivity and compared with an assay for SYBR Green I quantification using real-time fluorescence monitoring (PE Applied Biosystems Model 7700 sequence detector). SYBR Green I detection involved analysis of the melting temperature of the PCR product and measurement of fluorescence at the optimum temperature. Fluorogenic probes provided sensitive and reproducible detection of targets that ranged from low (<10 copies/reaction) to high (>107 copies/ reaction) expression. SYBR Green I gave reproducible quantification when the target gene was expressed at moderate to high levels (> or =1000 copies/reaction), but did not give consistently reproducible quantification when the target gene was expressed at low levels. Although optimization of melting temperature improved the specificity of SYBR Green I detection, in our hands it did not equal the reproducible sensitivity and specificity of fluorogenic probes. The latter method is the first choice for measurement of low-level gene expression, although SYBR Green I is a simple and reproducible means to quantify genes that are expressed at moderate to high levels.

Animals↗

PubMed2001

Immune activation is required for the induction of liver allograft tolerance: implications for immunosuppressive therapy.

Liver transplants in many animal models are unusual because often they are not rejected even when transplanted across complete major histocompatibility complex barriers without immunosuppression. Their paradoxical behavior is even more obvious when the immune mechanism of acceptance is examined. Instead of acceptance resulting from a lack of immune response to the graft, the opposite occurs, and there is an unusual extensive increase in immune activation in acceptance compared with rejection. This abnormal extensive immune activation is driven by donor leukocytes transferred with the liver and results in death of the recipient cells that would normally reject the transplant. Some forms of immunosuppression inhibit this activation-associated liver transplant tolerance. The significance of these findings and possible means to design future treatment protocols for clinical transplantation that optimize management of liver transplant recipients are discussed.

Animals↗

PubMed2001

Signaling by CD40 and its mimics in B cell activation.

CD40 is a member of the growing tumor necrosis factor receptor (TNF-R) family of molecules, and has been shown to play important roles in T cell-mediated B lymphocyte activation. Ligation of B cell CD40 by CD154 expressed on activated T cells stimulates B cell proliferation, differentiation, isotype switching, upregulation of surface molecules contributing to antigen presentation, development of the germinal center, and the humoral memory response. Several distinct structural motifs in the CD40 cytoplasmic domain regulate various CD40 signaling pathways, which involve both the TNF-R associated factors (TRAFs) and additional signaling proteins, and lead to activation of kinases and transcription factors. CD40-mediated B cell activation is mimicked by several biological response modifiers, as well as by a viral oncoprotein encoded by the Epstein-Barr virus (EBV).

Amino Acid Sequence↗

PubMed2001

Molecular mechanisms of CD40 signaling.

CD40, a member of the growing tumor necrosis factor receptor (TNF-R) family of molecules, functions as a transmembrane signal receptor in both hematopoietic and non-hematopoietic cell types, although its physiological roles are less well understood in the latter. Much has been learned over the past decade about the role of CD40 signaling in various cellular functions. In addition, some of the molecular events which occur subsequent to CD40 engagement have been characterized, although much remains to be understood. This review will summarize the known important biological roles of CD40, and discuss what is currently known about how CD40 signals.

Animals↗

PubMed2000

Corticotropin releasing factor induces proliferation of cerebellar astrocytes.

In the adult cerebellum, corticotropin releasing factor (CRF), that is localized in climbing fibers, mossy fibers, and a fine varicose plexus along the Purkinje cell layer, modulates the responsiveness of Purkinje cells to excitatory amino acids. During development, CRF has been detected in the primitive cerebellar anlage as early as embryonic day (E)10, and is continuously expressed throughout embryonic and postnatal cerebellar ontogeny. To investigate a possible trophic role for CRF during cerebellar development, cerebellar culture studies using E18 mouse embryos were carried out. In our culture paradigm, that used serum-free defined medium to suppress cell proliferation, CRF induced proliferation of cells in a dose-dependent manner in a range of concentrations between 0.1-10 microM. The proliferating cells were identified as astrocytes based on their expression of vimentin and GFAP. BrdU incorporation studies supported the proposed mitogenic effect of CRF on developing astrocytes. The mitogenic effects of CRF seemed to be primarily on immature astrocytes determined by their differential expression of vimentin and GFAP. Astrocytes at more advanced stages of development, as determined by the extent of process outgrowth and GFAP expression, incorporated less BrdU compared to immature astrocytes. CRF receptors were localized in astrocytes, and the proliferation of astrocytes induced by CRF was inhibited by astressin, a competitive CRF receptor antagonist. In conclusion, CRF induces proliferation of astrocytes derived from the developing cerebellum, that suggests a gliotrophic role for CRF during cerebellar development.

Animals↗

PubMed2000

Molecular mechanisms of B lymphocyte activation by the immune response modifier R-848.

The imidazoquinoline R-848, originally identified as a highly effective antiviral agent, has recently been shown to be capable of potent B lymphocyte activation. The B cell-activating properties of R-848 are strikingly similar to the effects of the CD40 ligand CD154. The present study demonstrates that this similarity extends to the intracellular signaling pathways triggered by the compound, although both overlapping and distinct mechanisms of signaling were seen. Like CD40 ligation, R-848 stimulated activation of the stress-activated protein kinases c-Jun kinase and p38 and activated the NF-kappaB family of transcription factors. Both R-848- and CD40-mediated B cell differentiation were dependent upon NF-kappaB activation, although the relative importance of individual NF-kappaB family members appeared to differ between R-848- and CD40-mediated signals. Both signals were partially dependent upon induction of TNF-alpha and IL-6, and the cytoplasmic adaptor molecule TNF receptor-associated factor 2 is involved in both R-848- and CD40-mediated differentiation.

Adjuvants, Immunologic↗

PubMed2000

Early up-regulation of macrophages and myofibroblasts: a new marker for development of chronic renal allograft rejection.

BACKGROUND: Increased numbers of macrophages and myofibroblasts are observed to occur in chronic renal allograft rejection (CR). The aim of this study was to examine the expression of cellular markers for the macrophage and myofibroblast in early renal transplant biopsy specimens and correlate these findings with allograft outcome. METHODS: The first postengraftment biopsy specimens from 53 patients who underwent renal transplantation between January 1993 and December 1995 were studied using immunohistochemistry with antibodies to alpha-smooth muscle actin, which identifies myofibroblasts and CD68, a marker for monocytes and macrophages. Patients were followed until December 1998 (mean follow-up 4.7+/-1.2 years). RESULTS: Nine patients had progressed to CR by the time of the study, whereas 44 patients continued to have stable renal function. A marked increase in both macrophages (P=0.02) and myofibroblasts (P=0.04) was noted in the first biopsy specimen obtained after engraftment in the patients who developed CR compared with those with stable allograft function. There was a positive correlation between alpha-smooth muscle actin and collagen expression (P=0.0001). CONCLUSION: Significant increases in macrophages and myofibroblasts occur in the first renal biopsy specimen in those patients who later develop CR.

Actins↗

PubMed2000

Recruitment of CD40 and tumor necrosis factor receptor-associated factors 2 and 3 to membrane microdomains during CD40 signaling.

Signals delivered to antigen-presenting cells through CD40 are critical for the activation of immune responses. Intracellular tumor necrosis factor (TNF) receptor-associated factors (TRAFs) are key elements of the signal transduction pathways of many TNF receptor family members, including CD40. We show for the first time that engagement of CD40 in intact B cells induces the rapid translocation of TRAF2 from the cytoplasm to the plasma membrane. We found that CD40 engagement also results in its recruitment, together with TRAF2 and TRAF3, to membrane microdomains, regions of the plasma membrane enriched in signaling molecules such as the Src family kinases. Using a membrane-permeable chelator of zinc or a mutant TRAF2 molecule, we show that the putative zinc-binding domains of TRAFs contribute to their recruitment to microdomains and to the downstream activation of c-Jun N-terminal kinase. We suggest that the zinc RING and zinc finger domains of TRAFs are required for communication between CD40 and microdomain-associated signaling molecules and may serve a similar role in the signal transduction pathways of other TNF receptor family members.

Animals↗