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Geoffrey W McCaughan

Publications and source records attributed to Geoffrey W McCaughan.

At least 37 records · Page 2Linked to original sources
PubMed2005

Early intrahepatic antigen-specific retention of naïve CD8+ T cells is predominantly ICAM-1/LFA-1 dependent in mice.

We have previously shown that naïve CD8+ T cells recognizing their cognate antigen within the liver are retained and undergo activation in situ, independent from lymphoid tissues. Intrahepatic primary T cell activation results in apoptosis and may play a crucial role in the ability of the liver to induce tolerance. Although adhesion molecules required for intrahepatic retention of T cells that have undergone previous extra-hepatic activation have been characterized, adhesive interactions involved in selective antigen-dependent intrahepatic retention of naïve CD8+ T cells have not been investigated. By adoptively transferring radiolabeled T cell receptor (TCR)-transgenic CD8+ T cells into recipient animals ubiquitously expressing the relevant antigen, we show that 40% to 60 % of donor antigen-specific naïve CD8+ T cells were retained in the liver within 1 hour after transfer, despite ubiquitous expression of the antigen. Intravital microscopy showed that most donor naïve T cells slowed down and were irreversibly retained intrahepatically within the first few minutes after adoptive transfer, strongly suggesting that they were directly activated by liver cells in situ. This process was largely dependent on LFA-1 and ICAM-1, but was independent of blocking with antibodies against VCAM-1, alpha4 integrin, P-selectin, VAP-1, and beta1 integrin. ICAM-2 seemed to play only a minor role in this process. Interestingly, LFA-1 expressed by both donor T cells and liver cells was involved in retention of the antigen-reactive T cells. In conclusion, LFA-1-dependent intrahepatic T cell retention and activation are linked events that may play a crucial role in the establishment of liver-induced antigen-specific tolerance.

Animals↗
PubMed2005

Development and resolution of experimental colitis in mice with targeted deletion of dipeptidyl peptidase IV.

Glucagon-like peptide-2 (GLP-2) is a potent intestinotrophic growth factor that enhances repair of damaged intestinal tissue. However, its bioactivity is limited by dipeptidyl peptidase IV (DPIV)-mediated degradation. We hypothesized that DPIV(-/-) mice would display an increased resistance to, and an enhanced recovery from, dextran sulfate sodium (DSS)-induced colitis compared to DPIV(+/+) mice. DPIV(+/+) and DPIV(-/-) mice consumed 2% DSS for 6 days, followed by a 15 day recovery period. Mice were killed at days 0, 3, 6, 9, 14, and 21 (n = 6-8) and the small intestine and colon removed for histological assessment of villus height, crypt depth, and crypt area. The epithelial cell proliferative labeling index was determined by proliferating cell nuclear antigen (PCNA) immunostaining. Small intestine, colon, and total body weight did not differ between DPIV(+/+) and DPIV(-/-) mice. Distal colon crypt depth did not differ significantly between DPIV(+/+) and DPIV(-/-) mice during the development of DSS-colitis or during the recovery phase. Similarly no significant effects were apparent on distal colon crypt area or PCNA labeling index between DPIV(+/+) and DPIV(-/-) during the development of and recovery from DSS-colitis. However, DPIV(-/-) mice still possessed significant levels of plasma DPIV-like activity. We conclude that loss of DPIV activity does not increase resistance to experimental colitis and hypothesize that other DPIV family members may also be involved in the cleavage of GLP-2.

Animals↗
PubMed2005

Intrahepatic immunity: a tale of two sites?

The intrahepatic immune environment is associated with the induction of tolerance, yet maintains the capacity to sustain effective responses against pathogens. The mechanisms underlying this dichotomy are unclear. Recent data indicate that activation of naïve CD8(+) T cells occurs within the liver. However, in contrast to efficient primary activation observed within the lymph nodes, this pathway is relatively ineffective, leading to reduced CD8(+) T-cell cytotoxicity and survival. Thus, the outcome of intrahepatic CD8(+) T-cell responses might be determined by whether primary activation occurs within the tolerogenic environment of the liver, or whether immunity is induced by initial antigen encounter within the lymph nodes. These findings support a novel model of hepatic-immune interactions, with implications for our understanding of the paradoxical nature of liver immunobiology.

Animals↗
PubMed2005

Parenchymal expression of CD86/B7.2 contributes to hepatitis C virus-related liver injury.

Hepatitis C virus (HCV) infection is a major global health problem. Hepatic expression of immune costimulatory signaling molecules (e.g., B7) is known to be associated with ongoing liver injury in hepatitis C patients. However, due to the general lack of viral culture systems and adequate animal models, the function of these molecules in disease pathogenesis is poorly understood. To investigate the role of CD86 in HCV-related liver injury, we developed two transgenic mouse lineages with inducible expression of HCV structural proteins and constitutive expression of the costimulatory molecule CD86/B7.2 in the liver. Using a hydrodynamic-based, nonviral delivery protocol, we induced HCV transgene expression in the livers of HCV and CD86 single- and double-transgenic mice. We found that hepatic CD86 expression resulted in increased activation of and cytokine production (e.g., interleukin-2 and gamma interferon) by CD4+ T cells and that the retention of these cells was associated with more pronounced necroinflammatory lesions in the liver. Taken together, these data suggest that augmented, parenchymal antigen presentation conferred by hepatocyte CD86 expression alters homeostasis and effector functions of CD4+ T cells and contributes to liver injury. This study provides an additional rationale for exploring immunomodulation-based therapies that could reduce disease progression in individuals with chronic HCV infection.

Animals↗
PubMed2005

Liver transplantation for viral hepatitis.

Viral hepatitis is associated with two forms of liver failure that may require liver transplantation: fulminant hepatic failure associated with all forms of acute viral hepatitis and chronic liver failure as a result of chronic hepatitis B and C infection (or both). This review briefly discusses liver transplantation for fulminant hepatitis but focuses on transplantation for hepatitis B- and hepatitis C-associated cirrhosis.

Antiviral Agents↗
PubMed2004

Dipeptidyl peptidase 9 has two forms, a broad tissue distribution, cytoplasmic localization and DPIV-like peptidase activity.

Dipeptidyl peptidase (DP) IV has a distinct substrate specificity in hydrolyzing a post-proline bond. Here we present novel data on the sizes and tissue distribution of human and rat gene products and the peptidase activity of the DPIV-related gene DP9. A short cDNA of 2589 bp and a long cDNA of 3006 bp of DP9 were cloned. A ubiquitous predominant DP9 mRNA transcript at 4.4 kb represented the short form, whereas a less abundant 5.0-kb transcript present predominantly in muscle represented the long form. Both forms of DP9 have no transmembrane domain and two potential N-linked glycosylation sites. DP9 exhibited post-proline dipeptidyl aminopeptidase activity and was a cytoplasmic, 110-kDa monomer. Thus, the six DPIV gene family members have diverse characteristics: only DP9 and DP8 have exclusively cytoplasmic localization and only DP9, DP8, fibroblast activation protein (FAP) and DPIV have peptidase activity.

Adenosine Deaminase↗
PubMed2004

Non-oxidative metabolism of ethanol by rat pancreatic acini.

BACKGROUND: The pathogenesis of alcoholic pancreatitis may involve the metabolism of ethanol (via oxidative and non-oxidative pathways) within the pancreas. The aims of this study were to determine the rate of non-oxidative metabolism in isolated rat pancreatic acini and to compare this to the rate of ethanol oxidation. METHODS: Pancreatic acini were isolated from male Sprague-Dawley rats and incubated with (14)C-ethanol. Radiolabelled fatty acid ethyl esters (non-oxidative metabolites) were isolated from lipid extracts by thin-layer chromatography. Radiolabelled acetate (oxidative metabolite) was isolated from the incubation medium by ion-exchange chromatography. RESULTS: Non-oxidative metabolism by isolated pancreatic acini was demonstrated. At 50 and 100 mmol/l ethanol, fatty acid ethyl ester concentrations were 49.6 +/- 13.3 and 199 +/- 93 micromol/l, respectively. These levels have previously been shown to result in tissue injury. Non-oxidative metabolism was increased 9-fold by addition of oleic acid and inhibited by the lipase inhibitor, tetrahydrolipstatin, by 91.05 +/- 1.99%. The rate of oxidative metabolism was 21-fold higher than that of non-oxidative metabolism. CONCLUSIONS: Intact pancreatic cells metabolize ethanol by the non-oxidative pathway, generating fatty acid ethyl esters at a rate sufficient to cause pancreatic damage. Oxidative metabolism of ethanol occurs at a much higher rate and may also play a role in pancreatitis.

Animals↗
PubMed2004

Improved prediction of fibrosis in chronic hepatitis C using measures of insulin resistance in a probability index.

We sought to develop a clinically useful index comprising standard and physiologically relevant variables to predict the probability of significant hepatic fibrosis in subjects with chronic hepatitis C virus (HCV) infection. Fibrosis was graded as mild (stages F0 or F1) or significant (stages F2-F4). Thirty-five clinical and laboratory parameters were analyzed initially in 176 patients with detectable HCV RNA to derive a fibrosis probability index (FPI) to predict significant fibrosis. This index then was validated in a second group of 126 subjects. Among 18 variables associated with severe fibrosis on univariate analysis, multiple logistic regression analysis identified age, aspartate aminotransferase (AST), total cholesterol level, insulin resistance (by homeostasis model), and past alcohol intake as independent predictors of significant fibrosis. The area under the receiver operating characteristic (ROC) curves was 0.84 for the initial cohort and 0.77 for the validation cohort. In the initial cohort, the sensitivity of the FPI based on these five predictors was 96%, and the negative predictive value was 93% at a score of >/=0.2. At scores >/=0.8, the FPI was 94% specific and had a positive predictive value of 87%. In conclusion, an FPI using routinely assessed markers and incorporating a measure of insulin resistance can reliably predict the probability of significant hepatic fibrosis in most patients with chronic HCV infection. Such an index should prove useful to guide decision making regarding the need for liver biopsy, and potentially for avoiding or deferring biopsy in a large proportion of patients with mild liver disease.

Adult↗
PubMed2004

Patient and graft survival after liver transplantation for hereditary hemochromatosis: Implications for pathogenesis.

The clinical outcome of patients who have undergone liver transplantation for hereditary hemochromatosis (HH) or who have received iron-loaded donor grafts is unclear. We reviewed 3,600 adult primary orthotopic liver transplants and assessed the outcomes in 22 patients with HH. We also evaluated graft function and iron mobilization in 12 recipients of iron-loaded donor grafts. All 22 subjects who received liver transplants for HH were male; 13 had other risk factors for liver disease. HH patients had comparatively poor outcomes following transplantation: survival at 1, 3, and 5 years posttransplantation were 72%, 62%, and 55%, respectively. Recurrent hepatocellular cancer was the most common cause of death. There was no convincing evidence of reaccumulation of iron in the grafted liver in HH; however, 1 subject demonstrated increased serum ferritin concentration and grade 2 hepatic siderosis. Liver iron stores were slow to mobilize in 7 of the 12 recipients of iron-loaded grafts. These recipients had appropriate early graft function, but 2 patients with heavy iron loading and increased hepatic iron developed hepatic fibrosis. In conclusion, (1) HH is an uncommon indication for liver transplantation, and the majority of patients requiring transplantation had other risk factors for chronic liver disease; (2) reaccumulation of liver iron in HH patients is very unusual, but increased iron stores may be slow to mobilize in normal recipients of iron-loaded grafts, potentially compromising late graft function; (3) post-liver transplant survival is reduced in HH, and affected patients require careful clinical evaluation of perioperative and postoperative risk factors. Our data suggest that iron excess in HH does not wholly depend on intestinal iron absorption but is also influenced by liver factors that moderate iron metabolism.

Adult↗
PubMed2004

A prospective cross-over study comparing the effect of mycophenolate versus azathioprine on allograft function and viral load in liver transplant recipients with recurrent chronic HCV infection.

It has been suggested that Mycophenolate Mofetil (MMF) may have an antiviral effect in patients with recurrent HCV infection post-liver transplantation. We conducted a prospective cross-over study in liver transplant recipients with recurrent chronic HCV infection to examine whether substitution of azathioprine (AZA) with MMF would reduce HCV load and improve allograft function. Thirteen long standing HCV liver transplant recipients receiving AZA were enrolled in a 9-month prospective cross-over study. In the initial 3 months lead-in period, baseline viral loads and biochemistry were recorded. Following this, MMF was substituted for AZA at a dose of 1 gm twice/day for a period of 3 months after which patients were switched back to AZA and observed for a further 3 months. Viral loads, biochemical allograft function, and adverse effects were closely monitored during the study period. Thirteen patients (12 males and 1 female) were enrolled. The mean age was 54 (+/-8) years and the mean time from transplantation was 68 (+/-35) months. Baseline mean viral load was 0.74 x 10(6)(+/-0.47 x 10(6)) messenger RNA (mRNA) copies/ml. By the end of the MMF treatment period, the mean viral load increased to a level of 1.64 x 10(6) (+/-1.3 x 10(6)) mRNA copies/ml (P = 0.026) compared to baseline. The increase in viral load however was not associated with an increase in ALT level. In a cohort of 13 HCV liver transplant recipients with recurrent chronic HCV infection, substitution of azathioprine with MMF did not lead to a decrease in viral load.

Azathioprine↗
PubMed2004

Increased mononuclear cell activation and apoptosis early after human liver transplantation is associated with a reduced frequency of acute rejection.

Experimental models of orthotopic liver transplantation (OLT) have shown that the very early events post-OLT are critical in distinguishing immunogenic and tolerogenic reactions. In rodents, increased leukocyte apoptosis and cytokine expression have been demonstrated in tolerogenic strain combinations. Information from human OLT recipients is less abundant. The aim of this study was to determine the amount of early leukocyte activation and apoptosis following human OLT, and to correlate this with subsequent rejection status. Peripheral blood mononuclear cells (PBMC) were isolated from 76 patients undergoing OLT - on the day prior, 5 hrs after reperfusion (day 0), and 18-24 hrs post-OLT (day 1). The mean level of apoptotic PBMCs on post OLT day 1 was higher than healthy recipients (0.9% +/- 0.2 vs. 0.2% +/- 0.1, p=0.013). Apoptosis was greater in nonrejecting (NR) (1.1% +/- 0.3) compared with acutely-rejecting (R) (0.3% +/- 0.1, p=0.021) patients. On day 1, PBMC from NR patients had increased expression of IFN-gamma (p=0.006), IL-10 (p=0.016), and CD40 ligand (p=0.02) compared with R. Donor cell chimerism on day 1 did not differ between the groups indicating that this was unlikely to account for increased PBMC apoptosis in the NR group. Interestingly, the level of chimerism on day 0 was significantly higher in NR (3.8% +/- 0.6) compared with R (1.2% +/- 0.4, p=0.004) patients and there was a close correlation between chimerism on day 0 and cytokine expression on day 1. These results imply that similar mechanisms are occurring in the human liver to promote graft acceptance as in the experimental models of liver transplantation and suggest that strategies that promote liver transplant acceptance in rodents might be applicable to humans.

Acute Disease↗
PubMed2004

Combined donor leucocyte administration and immunosuppressive drug treatment for survival of rat heart allografts.

BACKGROUND: Donor leucocytes (DL) play an important role in rat liver transplant tolerance and their postoperative administration can convert rejection to tolerance. They appear to induce early activation, altered patterns of infiltration and death of recipient alloreactive T cells. The ability of immunosuppressive drugs to combine with DL administration was examined in a rat heart transplant model. METHODS: Immediately after PVG to DA heterotopic heart transplantation, 6 x 10(7) spleen DL were injected. Cyclosporine A (CsA), 1.5 mg/kg/day, or methotrexate (MTX), 0.1 or 0.2 mg/kg/day, were given from day (d) 0 to d4 (early) or from d3 to d7 (delayed). Castanospermine (CAST) was administered from d0 to d7 at 100 or 300 mg/kg/day. In a separate experiment, transplanted hearts and recipient spleens were collected from treatment groups for analysis of infiltrate and cytokine mRNA expression. RESULTS: Delayed treatment with CsA or early treatment with MTX but not CAST combined with DL to result in prolonged graft survival. Recipients treated with DL and delayed CsA had a reduced level of intra-graft interleukin (IL)-2, interferon (IFN)-gamma, IL-4, and IL-4R mRNA expression and reduced infiltrate compared to DL alone. Early MTX plus DL led to almost complete inhibition of all markers of inflammation during treatment followed by a rapid increase after cessation. In combination with DL, CsA was more effective than MTX for induction of donor-specific tolerance at the dose and administration regimens tested. CONCLUSIONS: Delayed CsA or early MTX combine with DL to prolong heart allograft survival. Early and extensive inhibition of rejection by MTX was less effective than delayed and partial inhibition of the response by CsA for induction of transplant tolerance.

Adoptive Transfer↗
PubMed2004

The site of primary T cell activation is a determinant of the balance between intrahepatic tolerance and immunity.

Hepatic immunobiology is paradoxical: although the liver possesses unusual tolerogenic properties, it is also the site of effective immune responses against multiple pathogens and subject to immune-mediated pathology. The mechanisms underlying this dichotomy remain unclear. Following previous work demonstrating that the liver may act as a site of primary T cell activation, we demonstrate here that the balance between immunity and tolerance in this organ is established by competition for primary activation of CD8+ T cells between the liver and secondary lymphoid tissues, with the immune outcome determined by the initial site of activation. Using a transgenic mouse model in which antigen is expressed within both liver and lymph nodes, we show that while naive CD8+ T cells activated within the lymph nodes were capable of mediating hepatitis, cells undergoing primary activation within the liver exhibited defective cytotoxic function and shortened half-life and did not mediate hepatocellular injury. The implications of these novel findings may pertain not only to the normal maintenance of peripheral tolerance, but also to hepatic allograft tolerance and the immunopathogenesis of chronic viral hepatitis.

Adjuvants, Immunologic↗
PubMed2003

SMART amplification maintains representation of relative gene expression: quantitative validation by real time PCR and application to studies of alcoholic liver disease in primates.

The small quantities of tissue available for most studies of human disease are a significant limitation for meaningful gene expression profiling. The Atlas Switch Mechanism At the 5' end of Reverse Transcript (SMART) probe amplification kit uses as little as 50 ng of total RNA to generate complex cDNA probes for DNA array and other analyses. However, the extent to which this attractive methodology maintains representation of relative gene expression has not been quantified. In this study, we demonstrate using real-time quantitative PCR analysis that the relative expression levels of a range of low- to high-abundance mRNAs are retained after SMART amplification independent of transcript abundance and full-length transcript, coding region and PCR product size. Using this technology, a mean amplification of 3800-fold was achieved in human liver samples, greatly enhancing the ability to perform replicate DNA array experiments. Probes generated with the SMART amplification method were used to detect increased expression of genes involved with inflammation, fibrosis, xenobiotic metabolism, immune function, oxidant stress and endothelium in liver from the baboon model of alcoholic liver disease.

DNA, Complementary↗
PubMed2003

Structural requirements for catalysis, expression, and dimerization in the CD26/DPIV gene family.

Dipeptidyl peptidase IV (DP-IV/CD26), fibroblast activation protein (FAP), DP-like 1 (DPL1), DP8, DP9, and DPL2 comprise the CD26 gene family. CD26/DP-IV has roles in liver disease, T cell costimulation, chemokine biology, type II diabetes, and tumor biology. DPIV substrates include the glucagonlike peptides, neuropeptide Y, and the chemokines CCL3, CCL5, CCL11, CCL22, and CXCL12. We have proposed that the extracellular region of CD26 is analogous to prolyl oligopeptidase in consisting of an alpha/beta hydrolase domain contributed by both N- and C-terminal portions of the polypeptide and a seven-blade beta-propeller domain. Replacing the C-terminal portion of the predicted alpha/beta hydrolase domain of CD26 (residues 501-766) with the homologous portion of DP8 or DP9 produced intact proteins. However, these chimeric proteins lacked dimerization and peptidase activity, suggesting that CD26 dimerization requires the C-terminal portion of the alpha/beta hydrolase domain. Deleting some N-terminal residues of the alpha/beta hydrolase domain of CD26 ablated peptidase activity and greatly diminished cell surface expression. Together with previous data that CD26 peptidase activity requires the C-terminal 20 residues, this suggests that peptidase activity requires the entire alpha/beta hydrolase domain. The catalytic triad of DP8 was shown to be Ser(739)-Asp (817)-His(849). Glu(259) of DP8, a residue distant from the catalytic triad yet greatly conserved in the CD26 gene family, was shown to be required for peptidase activity. These data concord with our predicted CD26 structure, indicate that biosynthesis of a functional fragment of CD26 is difficult, and confirm the functional homology of DP8 with CD26.

Animals↗
PubMed2003

Dipeptidyl peptidase IV gene family. The DPIV family.

We have identified three novel members of the DPIV gene family using database mining approaches. Recombinant DP8 shares a post-proline dipeptidyl aminopeptidase activity with the closely related enzymes DPIV and FAP. The similarities between DP8, DP9 and DPIV in tissue expression pattern suggest a potential role for DP8 and DP9 in liver disease, T cell activation and immune function. The role of the two novel enzymes DP8 and DP9 and the other non-enzyme member DPL2 in human disease will be the focus of further studies.

Dipeptidyl Peptidase 4↗