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E Griffiths

Publications and source records attributed to E Griffiths.

At least 37 records · Page 2Linked to original sources
PubMed1998

Tumor defense by murine cytotoxic T cells specific for peptide bound to nonclassical MHC class I.

Cytotoxic T Cells (CTLs) can exhibit considerable antitumor activity. Thus far, the characterized tumor peptide antigens recognized by CTLs are all presented by classical MHC class Ia molecules [human lymphocyte antigen A (HLA-A), HLA-B, and HLA-C in humans and H-2K, H-2D, and H-2L in mice]. Here we show that CTLs recognized peptides presented by nonclassical MHC class Ib molecule Qa-1b expressed by tumor cells. These CTLs conferred in vivo protection by delaying the growth of Qa-1b-expressing B78H1 melanoma cells pulsed with Qa-1b-binding peptides Cw4L or B35L and injected s.c. in C57BL/6 mice. A hierarchy of the peptides was found with regard to their ability to trigger CTLs; Cw4L stimulated a strong CTL response. The closely related and cross-reactive peptide B35L induced a weaker CTL response but was still efficient in sensitizing the target cells. Finally, Qa-1b-expressing melanoma cells without exogenous peptides were not immunogenic but possibly expressed endogenous cross-reactive antigenic peptides. The data are compatible with earlier findings that CTL activation requires relatively strong peptide antigens, whereas subsequent effector functions are also mediated by weak peptide analogues. In conclusion, CTLs mediated tumor immunity through the recognition of peptides presented by nonclassical MHC class Ib molecules. The identification of similar CTLs in humans may facilitate the vaccination of cancer patients because MHC class Ib/peptide complexes are much less polymorphic than MHC class Ia/peptide complexes.

Animals↗
PubMed1998

Loss of cardiac magnesium in experimental heart failure prolongs and destabilizes repolarization in dogs.

OBJECTIVES: We sought to determine whether heart failure results in loss of cardiac magnesium sufficient to alter cellular electrophysiology. BACKGROUND: Free magnesium has numerous intracellular roles affecting metabolism, excitability and RNA synthesis. Total cardiac magnesium content is reduced in heart failure, but it is unclear whether magnesium loss is primary or iatrogenic. Furthermore, it is unknown whether free magnesium levels are affected or whether a change in free magnesium would alter cellular electrophysiology. METHODS: Eight mongrel dogs underwent demand ventricular pacing (VVI) at 250 beats/min for 3 weeks to induce heart failure. Sublingual epithelial magnesium was measured before pacing and at death. Left ventricular myocytes were isolated and loaded with Mag-Indo-1 to measure free magnesium ([Mg2+]i); myocytes from eight normal dogs served as controls. To test whether changes in [Mg2+]i in this range could alter cellular repolarization, current-clamped myocytes were dialyzed with 0.5 or 1.0 mmol/liter MgCl2. RESULTS: Mean sublingual epithelial magnesium fell significantly in the paced animals, from 36.9 +/- 0.5 to 33.9 +/- 0.7 mEq/liter (p < 0.01). Mean cardiac [Mg2+]i was significantly lower in the dogs with heart failure--0.49 +/- 0.06 versus 1.06 +/- 0.15 mmol/liter (p < 0.003). Time to 90% repolarization was significantly shorter in cells dialyzed with 1.0 mmol/liter compared with 0.5 mmol/liter MgCl2 in myocytes from normal dogs or dogs with heart failure (596 +/- 34 vs. 760 +/- 58 ms in normal dogs and 586 +/- 29 vs. 838 +/- 98 ms in dogs with heart failure; p < 0.05 for each). CONCLUSIONS: Experimental heart failure results in both tissue and cardiac magnesium loss in the absence of drug therapy. Free cardiac magnesium is significantly reduced, possibly contributing to abnormal repolarization in heart failure.

Action Potentials↗
PubMed1998

Immunogenicity of two efficacious outer membrane protein-based serogroup B meningococcal vaccines among young adults in Iceland.

Serum bactericidal activity (SBA) and ELISA antibody levels elicited by two efficacious serogroup B meningococcal vaccines were measured in a controlled trial involving 408 15- to 20-year-olds. Subjects were given two doses at a 6-week interval of a serogroup B or control vaccine. Response was defined as > or = 4-fold rise in antibody level. After two doses of the Finlay Institute (Havana) vaccine at 12 months, the proportions of SBA and ELISA responders were not different from those of the control group (15% and 17% [vaccine] vs. 13% and 9% [control], P > .05). After two doses of the National Institute of Public Health (Oslo) vaccine, there were more SBA and ELISA responders than in the control group (47% and 34% [vaccine] vs. 10% and 1% [control]) or the Finlay Institute vaccine group (P < .05 for both). SBA and ELISA may be insensitive correlates for protective efficacy for some outer membrane protein-based serogroup B meningococcal vaccines.

Adolescent↗
PubMed1998

Chromosome 22qII deletions. An under-recognised cause of idiopathic learning disability.

BACKGROUND: Velo-cardio-facial syndrome (VCFS), a syndrome of multiple congenital abnormalities including characteristic dysmorphology, congenital heart defects and learning disability, is associated with small interstitial deletions of chromosome 22qII. We tested the hypothesis that VCFS may be significantly under-diagnosed by screening a learning disabled population for chromosome 22qII deletions. METHOD: Two hundred and sixty-five people with learning disability residing in two learning disability hospitals in South Wales were reviewed. They were selected for inclusion in the study if they fulfilled any of the following criteria: psychotic disorder (schizophrenia or affective disorder), family history of psychotic disorder, cleft palate and/or lip, congenital heart disease, broadly defined facial dysmorphism or a history of hypocalcaemia. Fluorescence in situ hybridisation studies were performed on 74 selected individuals. RESULTS: Cytogenetic analysis revealed that two people demonstrated a previously undetected chromosome 22qII deletion. A third person demonstrated a previously undetected cytogenetically visible deletion on chromosome 15. CONCLUSIONS: VCFS appears to be aetiologically significant in a proportion of individuals with idiopathic learning disability, especially in those where psychosis is associated with mild learning disability. We suggest that clinicians should consider a chromosome 22qII deletion in people who meet selection criteria.

Adult↗
PubMed1997

TNF receptor p55 controls early acute graft-versus-host disease.

Allogeneic bone marrow transplantation is frequently associated with graft-vs-host disease (GVHD). To understand the effector mechanisms of GVHD, we investigated the role of the TNF receptor p55 (TNFRp55), which is known to be important in inflammation and cytotoxicity. After the transplantation of allogeneic bone marrow and spleen cells to lethally irradiated mice, all wild-type recipients developed early lethal GVHD within 1 wk, whereas TNFRp55-deficient recipients had much reduced GVHD and survived for at least 3 wk. No defect in alloantigen presentation was found, since T cell proliferation and cytotoxicity were similar to allogeneic wild-type and TNFRp55-deficient stimulator and target cells. Also, TNF alpha release did not differ significantly between the two types of recipients. Therefore, early acute GVHD in wild-type mice was primarily due to TNFRp55-mediated tissue damage. Interestingly, lethal GVHD was not entirely dependent upon the TNFRp55. In experimental conditions using sublethal irradiation and high donor spleen cell numbers, TNFRp55-deficient recipient mice developed lethal GVHD with similar kinetics and frequency as the control mice. These data suggest that the effector mechanisms leading to organ damage in murine acute GVHD can be dissected in a cytokine pathway through the TNFRp55, as demonstrated here, and in a cellular pathway through direct interaction of cytotoxic lymphocytes with target tissues involving perforin and Fas/Fas ligand, as reported previously.

Animals↗
PubMed1997

Concordance of bacterial cultures with endotoxin and interleukin-6 in necrotizing enterocolitis.

Concordance between gram-negative enteric and other toxin-producing bacteria in blood and stool culture, endotoxin (lipopolysaccharide), and interleukin-6 (IL-6) was measured in 60 preterm infants (600-1600 g) as a clinical index in neonatal necrotizing enterocolitis (NEC). E. coli, Klebsiella, Enterobacter, and Clostridium spp., identified by routine bacteriology, were each strongly associated with elevated concentrations of endotoxin (P < 0.01) in stool filtrates, with Clostridium spp. most strongly associated with NEC disease. Stool filtrate endotoxin (EU/g) measured by a Limulus amebocyte lysate assay was age dependent. Samples from stage I NEC (61%) and infants with advanced disease (67%) had notably elevated levels of stool endotoxin (> 10 ln EU/g) compared to NEC-negative (47%) samples tested. Plasma and stool IL-6 generally tested at the low, nonmeasurable limit of the ELISA for NEC-negative (88%) and stage I NEC (93%), although a small proportion of samples (25%) from infants with stage II or III NEC had elevated stool concentrations of IL-6. We conclude that identification of toxin-producing organisms and endotoxin elevations in stool filtrates are more useful than circulating levels of endotoxin in plasma in predicting mucosally limited disease in the gastrointestinal tract. The prognostic value of monitoring stool endotoxin in infants with overgrowth of gram-negative bacteria has implications for therapeutic strategies in patients with early and advanced stages of disease. Monitoring inflammatory cytokines (IL-6) in relation to endotoxin values in stool appears of limited clinical value in controlling this devastating disease in preterm neonates.

Endotoxins↗
PubMed1997

Assays for heparin-induced thrombocytopenia.

Tests for the presence of heparin-dependent antibodies (heparin-Ig) have evolved in parallel with improved understanding of the pathophysiology of heparin-induced thrombocytopenia (HIT). The first group of tests relied upon platelet aggregation or activation. Among tests in this group, the serotonin release assay has been reported to demonstrate the best performance characteristics. However, this test has not been widely adopted outside a few specialized laboratories owing to its complexity and need for radioactive materials. As a result, the less sensitive and specific platelet aggregation test is more commonly used for the diagnosis of heparin-Ig. The literature suggests that test sensitivity can be improved by the use of the patient's own platelets, platelets from selected donors known to be reactive in the assay, or washed platelets. Test specificity has been enhanced by the use of two point assays that include neutralization of the reaction by a high dose of heparin. A second group of assays have focused on detection of heparin-dependent binding of immunoglobulins to the platelet membrane. Most of these tests are hampered by the fact that platelets in patients with suspected HIT and in conditions that are in the differential diagnosis of HIT frequently express high levels of platelet-associated immunoglobulin. The most recent tests for heparin-Ig are based on the recognition that patient antibodies are directed against the heparin-PF4 complex. This has led to the development of the PF4/ heparin EIA assay. Because whole platelets are not used in this assay, problems related to under-reactivity or nonspecific reactivity are avoided. In addition, the ability of the test to predict clinical complications may be improved because the test can distinguish IgM from IgG heparin-Ig. Currently the laboratory diagnosis of heparin-Ig remains inexact. The sensitivity and specificity of laboratory assays cannot be firmly established. Much like the diagnosis of the phospholipid syndrome-where use of both the cardiolipin EIA and the lupus anticoagulant test offer overlapping advantages-the combination of the heparin-PF4 EIA plus either a test of platelet activation or a heparin-dependent antibody binding assay may prove to be a more sensitive and specific approach to the diagnosis of heparin-Ig. Despite the progress that has been made in the area of laboratory diagnosis of heparin-Ig, further improvement is needed. Heparin-induced thrombocytopenia is not rare and may be associated with devastating morbidity as well as mortality. Low-molecular-weight heparins usually cross-react with heparin-Ig. Therapy with Org 10172 appears to be the most promising alternative for patients with HIT. Because the clinical diagnosis is uncertain in sick hospitalized patients, further improvements in laboratory assays for heparin-Ig allowing earlier and more accurate diagnosis of patients at risk for HIT will be welcome.

Anticoagulants↗
PubMed1996

Conservation and antigenic cross-reactivity of the transferrin-binding proteins of Haemophilus influenzae, Actinobacillus pleuropneumoniae and Neisseria meningitidis.

Haemophilus influenzae acquires iron from the iron-transporting glycoprotein transferrin via a receptor-mediated process. This involves two outer-membrane transferrin-binding proteins (Tbps) termed Tbp1 and Tbp2 which show considerable preference for the human form of transferrin. Since the Tbps are attracting considerable attention as potential vaccine components, we used transferrin affinity chromatography to examine their conservation amongst 28 H. influenzae type b strains belonging to different outer-membrane-protein subtypes as well as six non-typable strains. Whole cells of all type b and non-typable strains examined bound human transferrin; whilst most strains possessed a Tbp1 of approximately 105 kDa, the molecular mass of Tbp2 varied from 79 to 94 kDa. Antisera raised against affinity-purified native H. influenzae Tbp1/Tbp2 receptor complex cross-reacted on Western blots with the respective Tbps of all the Haemophilus strains examined. When used to probe Neisseria meningitidis Tbps, sera from each of four mice immunized with the Haemophilus Tbp1/2 complex recognized the 68 kDa Tbp2 of N. meningitidis strain B16B6 but not the 78 kDa Tbp2 of N. meningitidis strain 70942. Serum from one mouse also reacted weakly with Tbp1 of strain B16B6. Apart from a weak reaction with the Tbp2 of a serotype 5 strain, this mouse antiserum failed to recognize the Tbps of the porcine pathogen A. pleuropneumoniae. However, a monospecific polyclonal antiserum raised against the denatured Tbp2 of Neisseria meningitidis B16B6 recognized the Tbps of all Haemophilus and Actinobacillus strains examined. Since H. influenzae forms part of the natural flora of the upper respiratory tract, human sera were screened for the presence of antibodies to the Tbps. Sera from healthy adults contained antibodies which recognized both Tbp1 and Tbp2 from H. influenzae but not N. meningitidis. Convalescent sera from meningococcal meningitis patients contained antibodies which, on Western blots, recognized the Tbps2s of both pathogens. These data demonstrate the existence of shared epitopes on the Tbps of H. influenzae, N. meningitidis and A. pleuropneumoniae despite their transferrin species specificity.

Actinobacillus pleuropneumoniae↗
PubMed1996

WHO activities towards the three Rs in the development and control of biological products.

WHO supports the concept of replacement, reduction and refinement of the use of in vivo methods for biologicals production and control, and regularly conducts reviews of its recommended procedures to allow reduction in the use of animals. The coordination of collaborative studies, publication of standardized methods, and holding of workshops on the use of these methods contributes to their use. The neurovirulence test for oral poliovaccine is probably the single most visible animal test for which alternative methods are sought. Collaborative studies on alternative methods for screening products are currently being sponsored by WHO. The use of Vero cells rather than primary monkey kidney cells for poliovaccine production can avoid the use of many monkeys. Cell banks of Vero and HEp-2 cells have been developed by WHO, tested for virus sensitivity and freedom from adventitious agents, and are available for vaccine production and control, replacing primary animal cells. For the future, final product testing will increasingly be directed towards establishment of consistency of production rather than potency. By supporting the validation and use of this approach, WHO can effectively influence more rational animal use in biological production and control.

Animal Testing Alternatives↗
PubMed1995

Haemoglobin-based blood substitutes and sepsis.

An important concern that has received little attention is the possible increased susceptibility to bacterial infections of patients infused with cell-free haemoglobin-based blood substitutes. We show that pyridoxalated polymerised human haemoglobin promotes fulminating Escherichia coli septicaemia in mice, which draws attention to the potential danger of such products in the clinic.

Animals↗