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Biomedical subjects

P Lane

Publications and source records attributed to P Lane.

At least 37 records · Page 2Linked to original sources
PubMed1999

CD4 T cell traffic control: in vivo evidence that ligation of OX40 on CD4 T cells by OX40-ligand expressed on dendritic cells leads to the accumulation of CD4 T cells in B follicles.

We report here that CD40- but not lipopolysaccharide (LPS)-activated murine dendritic cells (DC) express OX40-ligand (OX40L) as has been reported in humans. To understand how OX40 ligation affects differentiation of CD4 T cells at the time of priming, we constitutively expressed OX40L on DC using the DC-specific promoter of CD11c. Transgenic mice showed greatly increased numbers of CD4 but not CD8 T cells in their B cell areas. This effect was to a great extent immunization dependent, as spleen and lymphoid tissue with no germinal center reactions from mice which had not been deliberately immunized did not show marked CD4 T cell accumulation. The increased numbers of CD4+ CD62low cells in transgenic mice suggest that it is activated CD4 T cells that accumulate within B cell follicles. These data are consistent with the notion that physiological engagement of OX40 (CD134) on activated CD4 T cells either initiates their migration into or causes them to be retained in B follicles. In contrast, LPS-treated CD did not up-regulate OX40L expression. This dichotomy provides a molecular explanation of how DC might integrate environmental and accessory signals to control cytokine differentiation and migration in CD4 effector cells.

Animals↗
PubMed1999

The Wisdom Project: virtual education in primary care.

This article examines the development of the Wisdom Project, a pilot for the teaching of informatics to primary health care professionals, using an original educational model based on e-mail and Web pages. The article begins by placing the development of the Wisdom Project in the context of changes in medical education and training. The aims and objectives of Wisdom are outlined, and the methodologies for setting up and evaluating the project are described. The article then presents the results of the evaluation, including the identification of significant improvements in knowledge of CD ROMs (P = 0.01), e-mail (P = 0.03), Medline (P = 0.02), operating systems (P = 0.02), Web browsers (P = 0.003) and word processing (P = 0.03). Improvements in evidence-based practice (EBP) did not reach significance. Finally, a number of conclusions are presented, considering the lessons learnt for the future development of such projects.

Attitude to Computers↗
PubMed1999

Mice transgenic for a soluble form of murine cytotoxic T lymphocyte antigen 4 are refractory to murine acquired immune deficiency sydrome development.

Interactions between B and CD4+ T cells are central to the pathogenesis of retrovirus-induced murine acquired immune deficiency virus (MAIDS). Prompted by previous work showing that treatment with cytotoxic T lymphocyte antigen 4 immunoglobulin (CTLA4Ig) partly inhibited the disease, we studied the course of infection in mice deficient for CD28-B7 interactions (mCTLA4-Hgamma1 transgenic mice). Despite a relative viral load identical to that of non-transgenic mice, the transgenic mice did not develop any of the major MAIDS symptoms (i.e. lymphoproliferation and immune anergy). The mCTLA4-Hgamma1 did not however, completely inhibit B-cell activation as indicated by a slight hypergammaglobulinaemia and microscopic blastic transformation. Absence of MAIDS in transgenic mice was associated with much lower levels of both interleukin-4 and interferon-gamma transcripts following viral infection. These results support the theory that the CD28/B7 costimulatory pathway is a critical determinant to MAIDS development.

Abatacept↗
PubMed1999

The WISDOM project: training primary care professionals in informatics in a collaborative 'virtual classroom'.

OBJECTIVES: The WISDOM project applies Internet technologies to create a virtual classroom in health informatics for primary care professionals. Participants use a facilitated E-mail discussion list supported by a web site which provides on-line resources and an archive of teaching materials. DESIGN: The project took an adult-learning model in which participants identify their learning needs, emphasized using informatics skills in practice, and focused on skills likely to enhance evidence-based practice. The paper describes the project and an evaluation of the first programme which ran in 1997 with 28 participants. Pre- and post-intervention questionnaires were used to assess perceived skills in informatics and evidence-based practice. SETTING: University of Sheffield. SUBJECTS: Primary care professionals. RESULTS: Participants reported statistically significant increases in eight informatics skills. There were no significant changes in evidence-based practice skills. The web-site, seminar programme and discussion list were highly rated as useful in delivering informatics training. CONCLUSIONS: The WISDOM approach is effective for the delivery of informatics training to primary care professionals, and may be used more widely for other subjects and professional groups. There is a need for further research into facilitating virtual classrooms.

Education, Medical, Graduate↗
PubMed1999

Cell signaling by nitric oxide.

Appreciation of the role of nitric oxide (NO) in mammalian cell biology has toppled the paradigm that biological signaling is initiated exclusively by noncovalent, lock-and-key-type interactions with receptor proteins. Remarkably, nitric oxide is a free radical that signals by chemical reaction with its protein targets, resulting in covalent modifications and a stable alteration in protein structure and function. Although most proteins may be coerced to react with NO in vitro, the specific proteins that are functionally modified by NO within cells will depend on the concentration of NO and the composition of the intracellular milieu. A further level of complexity is introduced into NO signaling by the fact that reactions can occur with NO directly, or secondarily with NO-derived species. Much to the surprise of those who thought that reactive molecules are generated and act only under pathophysiological conditions (e.g., ischemia-reperfusion injury), NO has emerged as a prototype molecule that signals by chemistry in normal physiology. The unique attributes and importance of NO were recently recognized by the Nobel Prize Committee, with their decision to award the 1998 Prize in Medicine to Drs Furchgott, Ignarro, and Murad, pioneers in NO biology. This review surveys what we believe to be the most important mechanisms and targets of signaling by NO.

Animals↗
PubMed1998

CD4 T cell cytokine differentiation: the B cell activation molecule, OX40 ligand, instructs CD4 T cells to express interleukin 4 and upregulates expression of the chemokine receptor, Blr-1.

This report investigates the role of OX40 ligand (OX40L) and its receptor, OX40, expressed on activated B and T cells, respectively, in promoting the differentiation of T helper type 2 (Th2) CD4 T cells. These molecules are expressed in vivo by day 2 after priming with T cell- dependent antigens. Their expression coincides with the appearance of immunoglobulin (Ig)G switch transcripts and mRNA for interleukin (IL)-4 and interferon (IFN)-gamma, suggesting that this molecular interaction plays a role in early cognate interactions between B and T cells. In vitro, we report that costimulation of naive, CD62Lhigh CD4 T cells through OX40 promotes IL-4 expression and upregulates mRNA for the chemokine receptor, blr-1, whose ligand is expressed in B follicles and attracts lymphocytes to this location. Furthermore, T cell stimulation through OX40 inhibits IFN-gamma expression in both CD8 T cells and IL-12-stimulated CD4 T cells. Although this signal initiates IL-4 expression, IL-4 itself is strongly synergistic. Our data suggest that OX40L on antigen-activated B cells instructs naive T cells to differentiate into Th2 cells and migrate into B follicles, where T cell-dependent germinal centers develop.

Animals↗
PubMed1998

Requirements for B7-CD28 costimulation in mucosal IgA responses: paradoxes observed in CTLA4-H gamma 1 transgenic mice.

The block in the CD80/CD86-CD28/CTLA-4 pathway in CTLA4-H gamma 1 transgenic (Tg) mice results in strongly impaired systemic IgG immunity and failure to develop germinal center reactions. By contrast, here we report that mucosal immunity and IgA B cell differentiation are not affected by this block. We found abundant germinal centers and evidence of IgA switch differentiation in Peyer's patches, normal total IgA levels, and normal numbers of IgA-labeling cells in the gut mucosa. The distribution of B-1 and B-2 cells and the relative contribution of B-1 cells to the total IgA B cells were similar in Tg and wild-type mice. Despite this, oral immunizations with keyhole limpet hemocyanin plus cholera toxin adjuvant failed to stimulate Ag-specific mucosal IgA responses in CTLA4-H gamma 1 Tg mice. This was not due to a lack of adjuvant activity of cholera toxin in Tg mice, nor was this secondary to an inability to take up Ag from the gut lumen. Rather, CD4+ T cells stimulated by oral immunization in Tg mice appeared to be inappropriately primed, as evidenced by a significantly reduced level of CD40 ligand and CD44 expression and an increased expression of CD95 compared to those in wild-type mice. This study reveals a paradox in the regulation of mucosal IgA responses.

Abatacept↗
PubMed1997

An autoinhibitory control element defines calcium-regulated isoforms of nitric oxide synthase.

Nitric oxide synthases (NOSs) are classified functionally, based on whether calmodulin binding is Ca2+-dependent (cNOS) or Ca2+-independent (iNOS). This key dichotomy has not been defined at the molecular level. Here we show that cNOS isoforms contain a unique polypeptide insert in their FMN binding domains which is not shared with iNOS or other related flavoproteins. Previously identified autoinhibitory domains in calmodulin-regulated enzymes raise the possibility that the polypeptide insert is the autoinhibitory domain of cNOSs. Consistent with this possibility, three-dimensional molecular modeling suggested that the insert originates from a site immediately adjacent to the calmodulin binding sequence. Synthetic peptides derived from the 45-amino acid insert of endothelial NOS were found to potently inhibit binding of calmodulin and activation of cNOS isoforms. This inhibition was associated with peptide binding to NOS, rather than free calmodulin, and inhibition could be reversed by increasing calmodulin concentration. In contrast, insert-derived peptides did not interfere with the arginine site of cNOS, as assessed from [3H]NG-nitro-L-arginine binding, nor did they potently effect iNOS activity. Limited proteolysis studies showed that calmodulin's ability to gate electron flow through cNOSs is associated with displacement of the insert polypeptide; this is the first specific calmodulin-induced change in NOS conformation to be identified. Together, our findings strongly suggest that the insert is an autoinhibitory control element, docking with a site on cNOSs which impedes calmodulin binding and enzymatic activation. The autoinhibitory control element molecularly defines cNOSs and offers a unique target for developing novel NOS activators and inhibitors.

Amino Acid Sequence↗
PubMed1997

Regulation of T and B cell responses by modulating interactions between CD28/CTLA4 and their ligands, CD80 and CD86.

In recent years, it has become clear that the fate of lymphocyte interactions with antigen is determined not only by signals through antigen-specific receptors, but by interactions between pairs of accessory molecules. One such crucial pair of ligands is that between CD80/CD86, expressed by professional APCs and activated T and B cells, and CD28 (resting and activated T cells primarily) and CTLA4 (activated T cells). Signals in this system can amplify (CD28) or inhibit (CTLA4) T cell responses. The uses of soluble competitors for CD28 (CTLA4-Ig) and agonists for the inhibitory receptor CTLA4 (CD80-Ig) offer therapeutic possibilities to tailor autoimmune responses in nonpathogenic directions.

Abatacept↗
PubMed1997

Cardiac electrophysiology studies and ablation procedures: a literature review.

This literature review is focused on issues related to the development and usefulness of cardiac electrophysiology studies and ablation procedures. During the past decade, the efficacy of these developments has been proven. The resultant emergence of specialists trained as electrophysiologists represents an important milestone in the advancement of cardiology departments internationally. The majority of research papers on the subject have been published within the past 5 years. Most of the research has evolved from North America and Britain. On searching the literature, it was found that many gaps remain. There is a striking dearth of documented data regarding electrophysiology studies and ablation therapy within the Irish medical and nursing literature, and no previous literature review on the topic was found in a wider search. This paper provides an overview of the strengths and weaknesses associated with these procedures.

Arrhythmias, Cardiac↗
PubMed1997

Antiviral immune responses in CTLA4 transgenic mice.

The role of B7 binding CD28 in the regulation of T- and B-cell responses against viral antigens was assessed in transgenic mice expressing soluble CTLA4-Hgamma1 (CTLA4-Ig tg mice) that blocks B7-CD28 interactions. The results indicate that transgenic soluble CTLA4 does not significantly alter cytotoxic T-cell responses against replicating lymphocytic choriomeningitis virus (LCMV) or vaccinia virus but drastically impairs the induction of cytotoxic T-cell responses against abortively replicating vesicular stomatitis virus (VSV). While the T-independent neutralizing immunoglobulin M (IgM) responses were within normal ranges, the switch to IgG was reduced 4- to 16-fold after immunization with abortively replicating VSV and more than 30-fold after immunization with an inert VSV glycoprotein antigen in transgenic mice. IgG antibody responses to LCMV, as detected by enzyme-linked immunosorbent assay and by neutralizing action, were reduced about 3- to 20-fold and more than 50-fold, respectively. These results suggest that responses in CTLA4-Ig tg mice are mounted according to their independence of T help. While immune responses to nonreplicating or poorly replicating antigens are in general most dependent on T help and B7-CD28 interactions, they are most impaired in CTLA4-Ig tg mice. The results of the present experiments also indicate that highly replicating viruses, because of greater quantities of available antigens and by inducing as-yet-undefined factors and/or cell surface changes, are capable of compensating for the decrease in T help caused by the blocking effects of soluble CTLA4.

Abatacept↗
PubMed1997

Creating an education model for cardiac patients.

Patient education is important in reducing the risk of recurrence of myocardial infarction. Education should be specific to patients' individual needs. Patients need motivating to achieve the required behaviour changes. A multidisciplinary, multifactorial approach to education is most effective.

Humans↗
PubMed1996

Ligation of CD40 on dendritic cells triggers production of high levels of interleukin-12 and enhances T cell stimulatory capacity: T-T help via APC activation.

We investigated the possibility that T helper cells might enhance the stimulatory function of dendritic cells (DCs). We found that ligation of CD40 by CD40L triggers the production of extremely high levels of bioactive IL-12. Other stimuli such as microbial agents, TNF-alpha or LPS are much less effective or not at all. In addition, CD40L is the most potent stimulus in upregulating the expression of ICAM-1, CD80, and CD86 molecules on DCs. These effects of CD40 ligation result in an increased capacity of DCs to trigger proliferative responses and IFN-gamma production by T cells. These findings reveal a new role for CD40-CD40L interaction in regulating DC function and are relevant to design therapeutic strategies using cultured DCs.

Antigen-Presenting Cells↗
PubMed1996

Increase of intracellular calcium is the essential signal for the expression of CD40 ligand.

CD40 ligand (CD40L) is present on activated but not on resting T cells. In contrast to the activation markers CD25 and CD71, a strong CD40L expression could be induced by calcium ionophore alone but not by phorbol 12-myristate 13-acetate (PMA). Ionomycin induced a very early mRNA and protein surface expression of CD40L within the first 2 h, whereas CD25 and CD71 did not appear earlier than 6 h after stimulation. The mitogens phytohemagglutinin and concanavalin A induced little CD40L, but together with PMA, a markedly increased CD40L expression was observed. In T cells stimulated with immobilized anti-CD3, co-stimulation with anti-CD28 or PMA induced an earlier and higher maximal CD40L expression. CD40L expression of purified T cells was higher and more prolonged compared to that of T cells in unseparated peripheral blood mononuclear cells. We conclude that the expression of CD40L on T cells is profoundly different from other early activation markers with regard to signal requirements, kinetics and the role of accessory cells in the system.

Antibodies, Monoclonal↗
PubMed1996

Evidence that induction of tolerance in vivo involves active signaling via a B7 ligand-dependent mechanism: CTLA4-Ig protects V beta 8+ T cells from tolerance induction by the superantigen staphylococcal enterotoxin B.

Co-stimulation through CD28 is thought to be necessary for the activation of unprimed CD4+ T cells, which are otherwise rendered tolerant. However, we previously found that CD4+ T cell priming was normal or augmented in mice which overexpressed a soluble form of CTLA4 where co-stimulation through CD28 was abrogated. To investigate this CD4+ T cell response, we exploited the capacity of the superantigen staphylococcal enterotoxin B to stimulate T lymphocytes bearing V beta 8+, which represent approximately 30% of all CD4+ T cells. In litter-mate controls of CTLA4-Ig transgenic mice, immunization with staphylococcal enterotoxin B leads to expansion, followed by deletion of V beta 8+ T cells, and the remaining cells are tolerant when stimulated in vitro. Comparable expansion and deletion of V beta 8 T cells occurs in CTLA4-Ig transgenic mice. However, in contrast to normal mice, the remaining V beta 8+ T cells from CTLA4-Ig transgenic mice are not anergic and remain responsive to superantigen in vitro.

Abatacept↗
PubMed1996

CD28/CTLA4-B7 interaction is dispensable for T cell stimulation by mouse mammary tumor virus superantigen but not for B cell differentiation and virus dissemination.

B cells are the primary targets of infection for mouse mammary tumor virus (MMTV). However, for productive retroviral infection, T cell stimulation through the virally-encoded superantigen (SAG) is necessary. It activates B cells and leads to cell division and differentiation. To characterize the role of B cell differentiation for the MMTV life cycle, we studied the course of infection in transgenic mice deficient for CD28/CTLA4-B7 interactions (mCTLA4-H gamma 1 transgenic mice). B cell infection occurred in CTLA4-H gamma 1 transgenic mice as integrated proviral DNA could be detected in draining lymph node cells early after infection by polymerase chain reaction analysis. In mice expressing I-E, B cells were able to present the viral SAG efficiently to V beta 6+ T cells. These cells expanded specifically and were triggered to express the activation marker CD69. Further stages of progression of infection appeared to be defective. Kinetics experiments indicated that T and B cell stimulation stopped more rapidly than in control mice. B cells acquired an activated CD69+ phenotype, were induced to produce IgM but only partially switched to IgG secretion. Finally, the dissemination of infected cells to other lymph nodes and spleen was reduced and the peripheral deletion of V beta 6+ T cells was minimal. In contrast, in mice lacking I-E, T cell stimulation was also impaired and B cell activation undetectable. These data implicate B7-dependent cellular interactions for superantigenic T cell stimulation by low-affinity TCR ligands and suggest a role of B cell differentiation in viral dissemination and peripheral T cell deletion.

Abatacept↗
PubMed1996

Development of B-cell memory and effector function.

The past year has seen significant advances in our understanding of molecules that both positively and negatively regulate B- and T-cell responses. Of particular interest is the lethal phenotype of CTLA-4-deficient mice, which has illuminated the importance of downregulation of T-cell responses and the increasingly complicated role of CD40 and its ligand in directing both T- and B-cell priming.

Animals↗