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Biomedical subjects

J Hopkins

Publications and source records attributed to J Hopkins.

At least 145 records · Page 8Linked to original sources
PubMed1990

Cellular phenotypes in Trypanosoma congolense infected sheep: the local skin reaction.

Mononuclear cell subpopulations in local skin reactions (chancres) in sheep infected with metacyclic forms of Trypanosoma congolense were studied by indirect immunoperoxidase staining using a panel of monoclonal antibodies (MoAbs) specific for ovine leucocyte subsets. Morphometric analysis revealed significant increases in numbers of cells expressing CD5, CD4, CD8, CD45R (mainly B cells), major histocompatibility complex (MHC) class II antigens, Fc receptors (FcR) on macrophages (VPM32) and FcR on B cells and macrophages (VPM33) from five days post-infection. B cells which also expressed MHC class II were found mainly in dense aggregates. The CD4/CD8 ratios were raised over pre-infection levels at 5-7 days post-infection. In sheep which had been infected, treated with trypanocidal drugs and then challenged with an heterologous serodeme of T. congolense, changes in cellular phenotype kinetics were similar to those seen in the skin in primary infections. Sheep superinfected with either an homologous or an heterologous, T. congolense serodeme showed only mild cellular infiltration and slight increases in various cellular phenotypes at the sites of inoculation.

Animals↗
PubMed1990

Afferent lymph dendritic cells: a model for antigen capture and presentation in vivo.

We review the phenotypic and functional properties of sheep afferent lymph dendritic cells. These dendritic cells bear surface immunoglobulin and can acquire antigen/antibody complexes, both in vitro and in vivo. Our data suggest a role for Fc receptors in the capture of antigen by these cells. Dendritic cells collected after in vivo antigen pulsing are capable of stimulating T cell proliferation in an antigen-specific manner. Afferent dendritic cells express all the known groups of presentational molecules involved in activation of T cells, namely MHC class I and class II, and CD1. These results suggest a role for afferent dendritic cells in the activation of alpha beta and gamma delta T cells.

Animals↗
PubMed1990

IL-2-like activity in lymph fluid following in vivo antigen challenge.

The majority of studies that characterize lymphokines utilize in vitro activation of lymphocytes. In an attempt to identify and characterize lymphokines released from tissue sites, we have cannulated sheep lymphatic vessels and collected lymph that drains a site of in vivo antigen challenge. Lymph draining directly from a site of intradermal antigen challenge (afferent lymph) and lymph draining an antigen-stimulated lymph node (efferent lymph) were assayed for lymphokine activity by the ability of cell-free lymph fluid to stimulate the proliferation of sheep Con A-blasts. Afferent and efferent lymph, both collected at 24 and 48 hr following in vivo antigen challenge, with either ovalbumin or PPD in primed animals, stimulates the proliferation of sheep Con A-blast cells. This in vivo-derived lymphokine activity and in vitro-generated sheep Con A supernatant has an active component with properties similar to interleukin-2 (IL-2) that has been described in several other species. The IL-2-like material is precipitated by 40-80% ammonium sulphate saturation, has a molecular weight (MW) of 20,000 MW as judged by gel filtration chromatography, and is eluted from an anion-exchange HPLC column with 125 mM NaCl. HPLC ion-exchange fractionation of the 20,000 MW material from lymph fluid shows differences between afferent and efferent lymph material. The fractionation of afferent material is similar to that of in vitro generated Con A supernatant material with a single peak of activity eluted by 125 mM NaCl. In contrast, the 20,000 MW material from efferent lymph elutes with peaks of activity at 125 and 300 mM NaCl.

Animals↗
PubMed1990

Characterization of monoclonal antibodies specific for alpha- and beta-chains of sheep MHC class II.

In order to identify and characterize the sheep major histocompatibility complex (MHC) class II molecules, a panel of 19 monoclonal antibodies (mAb) has been raised following immunization of mice with a variety of class II antigen preparations. Antibodies were selected by ELISA using immunopurified sheep class II as antigen and further screened for the ability to react on immunoblots. Nine mAb reacted with the beta-chain and four reacted with the alpha-chain. The chain specificity of the remainder could not be determined as they did not blot. The anti-alpha and anti-beta mAb all reacted with deglycosylated class II. With the exception of one anti-alpha and one anti-beta antibody, the antibodies reacted with both efferent lymph cells and peripheral blood mononuclear cells (PBMC). Three of the anti-sheep class II mAb reacted with human PBMC.

Animals↗
PubMed1989

Comparative efficacy of terbutaline administered by Nebuhaler and by nebulizer in young children with acute asthma.

We compared the use of terbutaline sulphate that was delivered by a nebulizer with its delivery by a Nebuhaler at two dose levels in 27 children (nine children per group) of between three and six years of age with acute asthma. No significant difference was found in the mean baseline clinical score among the three groups, and a significant decline occurred in the mean clinical scores in all groups by 15 minutes which was maintained to 60 minutes after the dose was administered. The decline that was achieved with delivery of the drug by way of a Nebuhaler (at either dose level) was not significantly different from that with a nebulizer, although cooperation with Nebuhaler usage was not universal in the age-group.

Acute Disease↗
PubMed1989

Characterization of sheep afferent lymph dendritic cells and their role in antigen carriage.

We have ablated peripheral lymph nodes in sheep and subsequently cannulated the pseudo-afferent lymphatic vessel that arises as a consequence of afferent lymphatic vessels reanastomosing with the former efferent duct. This technique allows the collection of lymph with a cellular composition that resembles true afferent fluid, and in particular, containing 1-10% dendritic cells. A 16-h collection of this lymph may contain between 10(6) and 10(7) dendritic cells. This dendritic cell population may be enriched to greater than 75% by a single-density gradient centrifugation step. We have generated a mAb that recognizes sheep CD1. This monoclonal not only reacts with afferent dendritic cells, but with dendritic cells in the skin and paracortical T cell areas of lymph nodes. The expression of CD1 suggests afferent dendritic cells are related to skin Langerhans' cells and other dendritic cells that act as accessory cells for T cell responses. Consistent with this is the high level of expression by dendritic cells of molecules involved in antigen recognition by T cells, including MHC class I and class II. Afferent dendritic cells express high levels of the cellular adhesion molecule LFA-3, and at the same time express a ligand for this molecule, namely CD2. The accessory functions of afferent dendritic cells resemble those displayed by mature Langerhans' cells and by lymph node interdigitating cells. These include clustering with resting T cells and stimulating their proliferation in a primary response to antigen. Afferent dendritic cells are capable of acquiring soluble protein antigen in vivo or in vitro and presenting the material directly to autologous T cells in an antigen-specific manner. We conclude that afferent dendritic cells represent a lymph-borne Langerhans' cell involved in antigen carriage to the lymph node.

Animals↗
PubMed1989

In vivo modulation of CD1 and MHC class II expression by sheep afferent lymph dendritic cells. Comparison of primary and secondary immune responses.

The experiments described in this article characterize the phenotypic and functional changes in afferent lymph cell populations that occur as a result of in vivo immune stimulation. During the primary immune response (in antigen-naive sheep) there are very transient increases in level of CD1 expression by subpopulations of dendritic cells (DC) but no alterations in cell kinetics or MHC class II expression. In contrast, secondary antigenic challenge (in primed sheep) into the drainage area of an afferent lymphatic causes profound changes in the cell output, characterized by a greater than threefold drop in total cell output on days 1-3 followed by an approximate fivefold rise on day 5. There is also a substantial increase in both the proportion of MHC class II-positive T lymphocytes (from 28 to 54%) and in the quantitative expression of class II by both DC and lymphocytes. Class II expression by DC increases five- to sixfold by day 5, while the level of expression of class II on lymphocytes approximately doubles. The increase in CD1 expression during the secondary response is more prolonged than during the primary response, being detectable between days 2 and 6 after challenge. The rise in class II affects the whole DC population, in contrast to CD1 where the increase affects only a subpopulation of cells. In terms of functional properties, afferent lymph DC isolated during a primary response show no alteration of their activity, whereas DC taken 4-5 d after secondary challenge are up to fivefold more active in their ability to present soluble antigen to primed autologous T cells and to antigen-specific cell lines as well as to stimulate in the MLR. The relative expression of class II correlates temporally with an increased capacity of DC to present antigen. Monoclonal anti-class II antibodies totally inhibit the in vitro assays but anti-CD1 antibodies have no effect. The previous paper has demonstrated that afferent DC can associate with antigen in vivo and can present that antigen to antigen-specific T cells. This article extends our knowledge of DC biology and demonstrates that DC, activated during secondary in vivo immune responses, have an enhanced ability to present an antigen, unrelated to that used for challenge, to specific T cell lines. This enhancement correlates directly with quantitative variation of expressed class II and not CD1 and suggests that this variation in class II expression plays a physiological role in in vivo immune regulation.

Animals↗
PubMed1989

Generation of a sheep x mouse heterohybridoma cell line (1C6.3a6T.1D7) and evaluation of its use in the production of ovine monoclonal antibodies.

A stable aminopterin-sensitive sheep X mouse heterohybridoma cell line (1C6.3a6T.1D7) for use in the generation of sheep monoclonal antibodies is described. The line was first constructed by fusing the mouse myeloma line, NSO, to normal sheep lymphocytes obtained from the efferent lymphatic vessel of a cannulated popliteal lymph node. The line was rendered sensitive to aminopterin through a combination of irradiation and treatment with the anti-metabolite drug 6-thioguanine. Characterisation of the cloned cell line showed that it did not secrete sheep immunoglobulin (Ig) molecules, express Ig on the surface membrane, or express normal sheep B or T cell surface markers. The 1C6.3a6T.1D7 line has remained stable in tissue culture for over 2 years, showing no signs of reversion to aminopterin resistance. The 1C6.3a6T.1D7 cells have been used as fusion partners with lymphocytes from antigen primed sheep to generate sheep monoclonal antibodies to human chorionic gonadotropin (hCG) or a synthetic peptide analogue of the VP1 capsid protein of foot and mouth disease virus (FMDV). To optimise the efficiency of heterohybridoma generation, comparisons were made of peripheral blood, efferent lymph or excised lymph nodes as sources of antigen-stimulated lymphocytes for fusion. The results showed that lymphocytes prepared from either efferent lymph or lymph node on the fourth day following antigenic stimulation gave similar high fusion efficiencies, and both were vastly superior to peripheral blood lymphocytes. Results were also obtained which showed that the blast cells present in lymphoid tissues due to antigenic stimulation were the major cell types involved in the generation of viable antibody-secreting sheep X sheep X mouse heterohybridomas.

Aminopterin↗
PubMed1989

Non-random migration of CD4 and CD8 T cells: changes in the CD4: CD8 ratio and interleukin 2 responsiveness of efferent lymph cells following in vivo antigen challenge.

In this investigation we have examined some of the cellular and molecular changes in efferent lymph that drains from an antigen-stimulated peripheral lymph node. Resting efferent lymph is characterized by a higher percentage of CD4+ cells and consequently, a higher CD4/CD8 ratio than peripheral blood. Following antigen stimulation of a cannulated peripheral lymph node in antigen-primed sheep, the percentage of CD4+ cells in efferent lymph increases above the resting level during days 1, 2 and 3 post antigen stimulation. This is followed on days, 3, 4, and 5 after antigen stimulation by an increase in the percentage of CD8+ cells above the resting level which occurs as the percentage of CD4+ cells returns to the resting level. These changes cause the CD4/CD8 ratio to first increase above the resting value during the CD4 phase and then decrease below the resting value during the CD8 phase. During the CD4 phase a lymphokine activity is present in cell-free lymph fluid. Lymph fluid collected at this time supports the proliferation of activated T cells. Supernatants generated from efferent cells collected at a similar time and cultured in vivo for 24 h without any further stimulation are capable of releasing this material. During the CD8 phase cells expressing functional interleukin(IL)2 receptors appear in lymph fluid. The data suggests a sequential exit of T cell subsets from an antigen-stimulated lymph node and that the appearance of IL2-like activity and IL2-responsive cells in efferent lymph fluid are temporally distinct events.

Animals↗
PubMed1989

Obstetric outcomes at the birth place in Menlo Park: the first seven years.

During its first seven years of operation, the Birth Place, a free-standing birth center in California, registered 898 women, of whom 690 (77%) were admitted in labor and 150 (17%) were referred for hospital birth prior to onset of labor. Using carefully delineated screening criteria, the center had an overall 18% intrapartum transport rate to the hospital, primarily for prolonged or arrested labor, a 3% cesarean section rate, no maternal mortality, and one neonatal death resulting from Cornelia de Lange syndrome, a congenital mental retardation-malformation syndrome of unknown etiology, which in this case was incompatible with life. Deliveries at the Birth Place were associated with low cost, a high level of maternal satisfaction, a low cesarean section rate, low neonatal mortality, and no maternal mortality.

Ambulatory Care Facilities↗
PubMed1989

Lymphocyte subpopulations in the blood of sheep persistently infected with border disease virus.

The surface phenotypes of peripheral blood lymphocytes in groups of lambs and adult sheep persistently infected with Border disease virus (P-I BD) were compared with those of healthy controls. The proportion and number of lymphocytes bearing surface immunoglobulin (sIg+) and expressing class II MHC antigen (B cells) were significantly increased. A significant increase in CD1+ lymphocytes was also evident. Conversely, the proportion of T lymphocytes in P-I BD lambs was reduced. A marked reduction in the proportion of circulating lymphocytes expressing class I MHC antigen was also observed. These findings were not affected by differences in the strain of the virus responsible for the persistent infection.

Aging↗
PubMed1988

Recurrent ischemia in the zone of prior myocardial infarction: results of coronary angioplasty of the infarct-related artery.

We studied the efficacy of coronary angioplasty (PTCA) of the infarct-related artery in 54 patients with recurrent myocardial ischemia in the zone of prior infarction. Our patients had recurrent ischemia 10 +/- 7 days after infarction, with 75% experiencing rest angina and 15% having evidence of reinfarction. Angiography of the infarct-related artery demonstrated a critical stenosis in 35 of 54, a subtotal occlusion in 5 of 54, and a total occlusion in 14 of 54. PTCA was successful in 94% of critical stenoses, 80% of subtotal occlusions, but in only 50% of total occlusions. Complications related to PTCA included a 3.7% rate of emergency surgery, but no deaths or infarctions. During the clinical follow-up period of 11 +/- 7 months, there was one reinfarction and no deaths. Although 27% of our 44 patients with a successful initial PTCA required a second revascularization procedure for recurrent angina, 40 patients (91%) remained symptomatically improved with angioplasty alone (including successful repeat PTCA in eight patients). We conclude that PTCA of the infarct-related artery is beneficial for selected patients with recurrent ischemia in the zone of prior infarction.

Adult↗
PubMed1987

Percutaneous transluminal coronary angioplasty in patients with prior myocardial infarction: angioplasty at a distance from the prior infarct zone.

Patients undergoing coronary angioplasty who have had a prior transmural myocardial infarction in the distribution of a contralateral coronary artery are considered a high-risk group because of potentially severe left ventricular dysfunction if an ischemic complication occurs. The purpose of this study was to evaluate the safety and efficacy of coronary angioplasty in 28 patients with prior myocardial infarction remote from the artery undergoing dilatation. Prior myocardial infarction was defined by the presence of pathologic Q waves on ECG or segmental akinesis on ventriculography. Angioplasty was successful in 30 of 33 lesions (91%) and in 25 of 28 patients (89%). Mean stenosis diameter was reduced from 91% +/- 7% to 28% +/- 16%; mean translesional gradient after angioplasty was 6 +/- 5 mm Hg. No patient developed severe hemodynamic deterioration from transient coronary occlusion during balloon inflation or from an acute ischemic complication. Three patients underwent coronary artery bypass surgery after unsuccessful angioplasty. There were no new Q wave infarctions or deaths. The results of coronary angioplasty in patients with prior infarction were compared with those of 203 patients without prior remote infarction. Primary success and occurrence of major complications were comparable in both groups. At a mean follow-up of 12 +/- 6 months, 18 of the 25 patients (72%) who underwent initially successful dilatation have remained symptom free with angioplasty alone. Therefore, coronary angioplasty is a suitable therapeutic procedure in carefully selected patients with angina pectoris and prior myocardial infarction at a distance from the site of angioplasty.

Adult↗