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J Plum

Publications and source records attributed to J Plum.

At least 55 records · Page 3Linked to original sources
PubMed1999

Murine fetal natural killer cells are functionally and structurally distinct from adult natural killer cells.

Natural killer (NK) cell phenotype and activity was studied by analyzing uncultured and short-time-cultured murine NK cells from fetal day 17 spleen and thymus. In contrast to NK cells from adult mice, freshly sorted fetal NK cells did not contain NK receptor transcripts for Ly-49A, B, C/I, D, F, G2, or H. The only NK receptor transcripts that could be detected were Ly-49E and CD94. It is important that Ly-49E was present at a 10- to 30-fold higher level compared with uncultured NK cells from adult mice. After short-time interleukin-2 culture, the level of Ly-49E mRNA was comparable between fetal and adult NK cells. Functionally, fetal NK cells only killed MHC class I-negative tumor cells when activating NK receptors were cross-linked with antibody. We show that fetal NK cells are mature but are different from NK cells in adult mice regarding their NK cell receptor repertoire and function.

Animals↗
PubMed1999

Developmentally regulated responsiveness to transforming growth factor-beta is correlated with functional differences between human adult and fetal primitive hematopoietic progenitor cells.

Important functional differences exist between primitive CD34++ CD38- hematopoietic progenitor cells derived from human fetal liver (FL) and adult bone marrow (ABM). FL progenitors are known to have higher proliferative capacities and lower cytokine requirements than their ABM counterparts. In this study, we isolated FL and ABM CD34++ CD38- cells and used a two-stage culture system to investigate the effects of transforming growth factor-beta (TGF-beta) and blocking anti-TGF-beta antibodies (anti-TGF-beta) on these cells. First, we demonstrate that FL progenitors are significantly less sensitive to the inhibitory effects of TGF-beta than ABM cells. Second, whereas ABM cells are significantly stimulated by anti-TGF-beta, only very limited effects are seen on FL cells. Third, we show that the effect of anti-TGF-beta is mainly situated at the level of the initial cell cycles of very primitive progenitor cells with a high proliferation potential. Fourth, we demonstrate that blocking the effects of endogenous TGF-beta reduces the growth factor requirements of ABM cells in order to proliferate and differentiate. Based on these data, we hypothesize that at least part of the functional differences that exist between adult and fetal stem cells can be accounted for by a developmental different responsiveness to TGF-beta.

Adult↗
PubMed1999

Bone marrow CD34 cells generate fewer T cells in vitro with increasing age and following chemotherapy.

To assess the influence of high-dose chemotherapy and age on the intrinsic capacity of stem cells to generate T cells, CD34+ cells derived from bone marrow used in clinical transplantation were evaluated in an in vitro T-cell assay using a mouse thymic microenvironment. CD34+ cells were sorted from healthy donor and autologous back-up bone marrow after density gradient centrifugation and depletion for CD1, 3, 4, 7, 8, 19 and glycophorin A using magnetic beads. CD34+ cells were then introduced in day 14-15 fetal SCII) mouse thymus lobes by incubation in hanging drops for 48 h. After transfer to gelfoam rafts they were cultured for variable time periods. The lobes were then homogenized in a tissue grinder for flow cytometric analysis gating on human cells. These were evaluated for CD4, CD8, CD3 and HLA-DR surface expression. 51 samples were analysed and three patterns of T-cell precursor development could be observed. In pattern A no human cells could be recovered, in pattern B maturation stopped at the CD4+ CD8- CD3- pre-T-cell stage, and in pattern C maturation to double-positive CD4+ CD8+ thymocytes was reached. In 25 healthy donors under age 40 three showed pattern A, 12 pattern B and 10 pattern C, whereas in 16 healthy donors over the age 40 there were respectively four with A, seven with B and only five with C (P=0.01). In 10 patients who had previously received chemotherapy, none developed pattern C, five pattern B and five pattern A, in contrast to 15/41 pattern C, 19/41 pattern B and 7/41 pattern A in healthy donors. These data suggest an intrinsic loss of T-cell generation capacity from adult bone marrow stem cells in comparison to reports on stem cells of fetal origin. This loss correlated weakly with age, irrespective of thymic involution, and may be further reduced by prior chemotherapy.

Adult↗
PubMed1999

Anticoagulation with r-hirudin in a patient with acute renal failure and heparin-induced thrombocytopenia.

After a Caesarean section subcutaneous bleeding with a secondary infection occurred accompanied by acute renal failure. Additionally the diagnosis of a heparin-induced thrombocytopenia type II could be made. Therefore, haemodialysis treatments were performed with r-hirudin as an alternative anticoagulation. Even in dialysis dependent acute renal failure a safe anticoagulation with r-hirudin is possible if aPTT and plasma r-hirudin are closely monitored.

Acute Kidney Injury↗
PubMed1999

[Can T-cell immunity in an adult be regenerated?].

In man, normal peripheral T cell function depends on thymopoiesis during the foetal and perinatal period (up to 3 months). In humans, studies have shown that declines in thymic T-cell regenerative capacity begins relatively early in life, resulting in a limited capacity for T-cell regeneration by young adulthood. These limitations in T-cell regeneration have significant clinical implications in the setting of HIV infection and bone marrow transplantation. Recent studies have reported that the human thymus can generate new cells throughout life, and even late, into adult life. Patients infected with HIV can generate new peripheral T cells after anti-viral therapy. In view of a continuous role of thymopoiesis in man, there is a growing need for relevant models of human thymopoiesis. Using a hybrid human-mouse FTOC model, we have shown that IL-7 is an essential growth factor for thymocytes and that certain genes of HIV interfere with the normal production of thymocytes. These studies allow the selection for products active in therapeutic restoration or maintenance of thymic function.

Adult↗
PubMed1999

Nitric oxide production in peritoneal macrophages from peritoneal dialysis patients with bacterial peritonitis.

Nitric oxide (NO) is produced by various cell types, and it is an important mediator in many biological processes, including macrophage-mediated cellular host defense. The relevance and amount of NO production in peritonitis during peritoneal dialysis (PD) treatment is still not clear. We studied whether human peritoneal macrophages (PMphi) isolated from healthy PD patients or PD patients with peritonitis showed different spontaneous or lipopolysaccharide (LPS)/interferon gamma (IFN-gamma)-induced NO production (LPS, 1 ng/mL-10 microg/mL; IFN-gamma, 10-1000 U/mL; incubation between 6-48 hours; measured by Griess reagent). Results were compared with human blood monocytes (HBM) isolated from buffy coats. Inducible nitric oxide synthetase (iNOS) mRNA expression was looked for in PMphi by reverse transcriptase polymerase chain reaction (RT-PCR). Furthermore, plasma (P) and peritoneal dialysate effluent (D) nitrite concentrations were measured in vivo. The dialysate-to-plasma ratio (D/P) of nitrite concentration was inverse in the case of peritonitis compared to infection-free patients (peritonitis D/P = 1.3, non peritonitis D/P = 0.4; p < 0.01). PMphi from peritonitis patients produced higher amounts of NO than did those from infection-free patients (0.040+/-0.044 nmol per microgram cell protein versus 0.018+/-0.015 nmol per microgram cell protein, p < 0.05). NO release could not be further enhanced by stimulation with LPS plus IFN-gamma (1 ng/mL, 250 U/mL, respectively). However, NO production in PMphi from infection-free patients increased during in vitro stimulation (0.044+/-0.031 nmol per microgram cell protein versus 0.018+/-0.015 nmol per microgram cell protein, p < 0.01). An increase of iNOS mRNA expression could be demonstrated by RT-PCR. Blood monocytes from healthy donors also increased NO release during cytokine stimulation (0.032+/-0.015 nmol per microgram cell protein versus 0.019+/-0.009 nmol per microgram cell protein, p < 0.05). Our results indicate that significant amounts of NO are released intraperitoneally in the case of bacterial peritonitis. PMphi represent a site of NO production, though the absolute amounts released in vitro are only moderate. NO production can be induced in PMphi and HBM by LPS/IFN-gamma stimulation in vitro.

Adult↗
PubMed1998

Haptoglobin polymorphism, iron metabolism and mortality in HIV infection.

BACKGROUND: Three phenotypes of the antioxidant protein haptoglobin are known: Hp 1-1, Hp 2-1 and Hp 2-2. OBJECTIVES: To investigate the outcome of HIV infection according to haptoglobin type. DESIGN AND METHODS: Haptoglobin phenotypes were determined using starch gel electrophoresis in serum obtained from 653 HIV-infected Caucasians in the AIDS reference centers of Gent (n = 184), Antwerp (n = 309), and Luxembourg (n = 160). Survival was compared between haptoglobin types using Kaplan-Meier curves. Plasma HIV-1 RNA was quantified by reverse transcriptase PCR. Serum iron, transferrin saturation, ferritin, and vitamin C were assayed to evaluate iron-driven oxidative stress in 184 HIV-infected patients and 204 controls. RESULTS: The haptoglobin type distribution amongst the patients (17.6% Hp 1-1, 49.9% Hp 2-1, 32.5% Hp 2-2) corresponded to that of the controls. Kaplan-Meier curves showed a higher mortality for the Hp 2-2 group (P = 0.0001; adjusted mortality risk ratio, 1.78; 95% confidence interval, 1.25-2.54). Median survival time was 11.0 years (Hp 1-1 and Hp 2-1) versus 7.33 years (Hp 2-2). Plasma HIV-1 RNA levels prior to antiviral therapy and their increase over 1 year were highest in Hp 2-2 patients (P = 0.03 and 0.003, respectively). The Hp 2-2 type was associated with higher serum iron, transferrin saturation, and ferritin levels and with low vitamin C concentrations. Furthermore, ferritin concentrations were higher in HIV-infected patients than in controls (P < 0.0001). CONCLUSION: HIV-infected patients carrying the Hp 2-2 phenotype show a worse prognosis, which is reflected by a more rapid rate of viral replication (in the absence of antiviral treatment). They also accumulate more iron and oxidize more vitamin C, suggesting that less efficient protection against haemoglobin/iron-driven oxidative stress may be a direct mechanism for stimulating viral replication.

Adult↗
PubMed1998

Retrovirally transduced CD34++ human cord blood cells generate T cells expressing high levels of the retroviral encoded green fluorescent protein marker in vitro.

Human umbilical cord blood (UCB) hematopoietic stem cells (HSC) receive increased attention as a possible target for gene-transfer in gene therapy trials. Diseases affecting the lymphoid lineage, as adenosine deaminase (ADA) deficiency and acquired immunodeficiency syndrome (AIDS) could be cured by gene therapy. However, the T-cell progenitor potential of these HSC after gene-transfer is largely unknown and was up to now not testable in vitro. We show here that highly purified CD34++ Lineage marker-negative (CD34++Lin-) UCB cells generate T, natural killer (NK), and dendritic cells in a severe combined immunodeficient mouse fetal thymus organ culture (FTOC). CD34++Lin- and CD34++CD38-Lin- UCB cells express the retroviral encoded marker gene Green Fluorescent Protein (GFP) after in vitro transduction with MFG-GFP retroviral supernatant. Transduced cells were still capable of generating T, NK, and dendritic cells in the FTOC, all expressing high levels of GFP under control of the Moloney murine leukemia virus (MoMuLV) long terminal repeat promotor. We thus present an in vitro assay for thymic T-cell development out of transduced UCB HSC, using GFP as a marker gene.

Animals↗
PubMed1998

Effect of alternative peritoneal dialysis solutions on cell viability, apoptosis/necrosis and cytokine expression in human monocytes.

BACKGROUND: Cellular function, cell viability and the cytokine network of human monocytes are influenced by the specific composition of peritoneal dialysis (PD) fluids. In an in vitro study using isolated human blood monocytes, we investigated the effect of peritoneal dialysates containing amino acids (Amino) or glucose polymer (Glu-poly) instead of glucose (Glu) as the osmotic agent, and bicarbonate (Bic) or PBS instead of lactate (Lac) as a buffer. METHODS: The following parameters were studied: mitochondrial dehydrogenase activity (using the MTT assay), interleukin (IL)-6 and IL-8 release (ELISA) and cellular IL-6 mRNA expression after lipopolysaccharide (LPS) stimulation (using RT-PCR). FACS flow cytometry with annexin V and propidium iodide as markers and fluorescence microscopic methods were used to study the effects of the test fluids on cell necrosis and apoptosis. RESULTS: Glu/Lac pH 5.5 and Glu-poly/PBS pH 7.4 both significantly reduced mitochondrial dehydrogenase activity by more than 50% after 60 minutes of incubation (30.5 +/- 7.6%, 42.5 +/- 6.5%, referred to RPMI 1640 as 100%). Amino/Bic and Glu/Bic were both superior (Mtt assay > 63%). The rate of necrotic cells after 15 minutes of incubation measured by FACS was mostly increased with Glu/Lac pH 5.5 (29.9 +/- 4.0%). The rate of apoptotic cells, however, was not significantly different between the test solutions. The concentration of IL-6 in the supernatant of stimulated monocytes was highest with Glu/Bic (1023 +/- 278 pg/ml) and Amino/Bic (776 +/- 296 pg/ml) an lowest with Glu/lac pH 5.5 (46 +/- 22 pg/ml) and Glu-poly/PBS (32 +/- 13 pg/ml). IL-8 release from stimulated monocytes showed a similar pattern. Glu-poly/PBS showed a suppressive effect on IL-6 mRNA expression (ratio IL-6/beta-Actin, 0.4 +/- 0.25 vs. RPMI 1.5 +/- 3.6). CONCLUSIONS: Bicarbonate buffered solutions both with glucose or amino acids as osmotic agents were superior when regarding cell metabolism, viability and cytokine release, while lactate buffered solutions and Glu-poly/PBS showed some reduced biocompatibility pattern for monocytes in vitro.

Actins↗
PubMed1998

Effects of the angiotensin II antagonist valsartan on blood pressure, proteinuria, and renal hemodynamics in patients with chronic renal failure and hypertension.

Angiotensin II receptor antagonists have become clinically available for the treatment of arterial hypertension. Presently, there is little information about their effects on BP, proteinuria, and renal function in patients with moderate or advanced renal failure. This study examines the effects of the angiotensin II antagonist Valsartan (80 mg/d) on proteinuria and glomerular permselectivity in patients with chronic renal failure during a 6-mo treatment, using a double-blind, randomized, placebo-controlled study (treatment group [V-group]: n = 5, age 57 +/- 7 yr, serum creatinine 365 +/- 122 micromol/L; placebo group [P-group]: n = 4, age 62 +/- 11 yr, serum creatinine 346 +/- 61 micromol/L). Study parameters included BP, 24-h proteinuria, GFR, and effective renal plasma flow (ERPF) as determined by inulin and para-aminohippurate clearance. Changes in glomerular permselectivity were assessed by measuring the fractional clearances of neutral dextrans by HPLC gel-permeation chromatography. Valsartan lowered the mean arterial pressure on average by 13 +/- 7 mmHg during the 6-mo treatment (P < 0.05). GFR and ERPF remained almost unchanged. However, after 6 mo of Valsartan treatment, proteinuria was reduced by 396 +/- 323 mg/24 h (26 +/- 18%) and albuminuria by 531 +/- 499 mg/24 h (41 +/- 21%) with regard to baseline values (P < 0.05). In the P-group, both proteinuria and albuminuria increased slightly with time (by 30 +/- 43% and 30 +/- 54%, respectively, NS). The fractional clearances of high molecular weight dextrans >66 A were significantly reduced after 6 mo of Valsartan treatment (P < 0.05), indicating a reduction of the glomerular shunt volume by 54 +/- 20% (P < 0.05) according to the model of Deen et al. (Am J Physiol 249: 347-389, 1985). The mean pore size radius of the glomerular membrane remained unchanged. This effect was independent of glomerular hemodynamic changes. Valsartan persistently lowered proteinuria in patients with chronic renal failure. Although GFR and ERPF remained nearly stable, this effect could be attributed to an improvement in glomerular permselectivity.

Aged↗
PubMed1998

The role of interleukin-7 in early T-cell development.

Interleukin-7 (IL-7) is a non redundant cytokine in thymic T-cell development. It binds to a dimeric receptor consisting of a specific IL-7Ralpha and a gamma-common subunit that it shares with the receptors for IL-2, 4, 9, 13 and 15. IL-7 is critical for early T-cell development but it also acts on immature B-cells and mature T-cells, and leads to secondary cytokine release. Its mechanisms of action in early T-cell development may be multiple. There is direct evidence to support a mechanistic involvement in TCR-gamma rearrangement that drives further TCR-gammadelta thymocyte commitment and maturation. There is indirect evidence for a role of IL-7 in TCR-beta rearrangement. It may however also act as a survival factor for TCR-beta rearranging thymocytes while the critical commitment selections are effected by other factors. The effects of IL-7 in fetal thymus organ culture are dose dependent, with a biphasic response: low doses of IL-7 are necessary for normal TCR-alphabeta thymocyte development but high doses block TCR-alphabeta maturation in favor of TCR-gammadelta development. A good understanding of the dose response of IL-7 in thymocyte development, mature T-cell stimulation, and of the release of secondary cytokines will be important for planning successful clinical trials with IL-7.

Antigen-Antibody Reactions↗
PubMed1998

CD34++ CD38- and CD34+ CD38+ human hematopoietic progenitors from fetal liver, cord blood, and adult bone marrow respond differently to hematopoietic cytokines depending on the ontogenic source.

CD34++ CD38- and CD34+ CD38+ hematopoietic progenitor cells (HPCs) from human fetal liver (FL), cord blood (CB), and adult bone marrow (ABM) were isolated and investigated for their growth characteristics, cytokine requirements and response to two modulators of early hematopoiesis, interferon (IFN)-gamma and macrophage inflammatory protein (MIP)-1alpha. We observed first that a significantly lower percentage of CD34++ cells were CD38- in ABM than in FL and CB. Second, the functional differences between CD34++ CD38- and CD34+ CD38+ cells were less pronounced in FL and CB than in their ABM counterparts. Third, an inverse correlation was found between growth factor response and the ontogenic age of HPCs, and a direct correlation was noted between cytokine requirements and the ontogenic age of HPCs. Fourth, spontaneous colony formation in a classic semisolid culture system was reproducibly obtained only in the ontogenically earliest cells, that is, in FL but not in CB and ABM, in which no such spontaneous colony formation was observed. Fifth, the modulatory effects of IFN-gamma and MIP-1alpha were qualitatively different depending on the ontogenic age of the progenitor source: whereas IFN-gamma was only a selective inhibitor of primitive CD34++ CD38- ABM progenitor cells, it inhibited both CD34++ CD38- and CD34+ CD38+ FL and CB cells to the same extent. In contrast to the effects of MIP-1alpha on ABM, we could not find any consistently stimulatory or inhibitory effects on FL and CB progenitors. In conclusion, important functional and biologic differences exist between FL, CB, and ABM progenitor cells, and these differences could have major implications for the use of these cell populations in preparative protocols of ex vivo expansion, transplantation strategies, or gene transfer experiments.

ADP-ribosyl Cyclase↗
PubMed1997

Human thymocytes become lineage committed at an early postselection CD69+ stage, before the onset of functional maturation.

Mature functional CD4 or CD8 single positive (SP) thymocytes differentiate from immature CD4+ 8+ double positive (DP) precursors through a process of positive selection and terminal differentiation. To study CD4/CD8 lineage commitment, human postselection CD69+ thymocytes were separated into distinct subpopulations based on the differential expression of CD27, CD1, and CD45RA/RO. We demonstrate that these CD69+ subpopulations represent transitional stages of a common differentiation pathway during which CD69+ thymocytes that are initially CD27- CD1+ CD45RA- will sequentially up-regulate CD27, down-regulate CD1, and eventually acquire CD45RA upon maturation. Examination of CD4 and CD8 expression on these CD69+ subsets identified an early postselection CD69+ CD27- CD4SP population that gives rise to both CD4SP and CD8SP mature T cells when cultured in mouse thymus organs. In addition, a CD4+ 8+ DP population was identified that is CD69+ and CD27+, which only gives rise to CD8SP progeny upon culture. Although these results suggest that development of CD4SP and CD8SP cells may proceed through distinct intermediates, examination of active biosynthesis of CD4 and CD8 by the various subsets demonstrated that cells that have selectively terminated CD4 synthesis are already present in the CD27- CD4SP and CD27+ DP populations before culture. These data support a model of thymocyte differentiation whereby the decision of thymocytes to differentiate into one or the other lineage occurs concomitantly with, or very soon after, acquisition of CD69 and before the cells acquire CD27, down-regulate CD1, or acquire functional properties.

Animals↗
PubMed1997

Phenotypic and functional maturation of TCR gammadelta cells in the human thymus.

In contrast to thymic differentiation of TCR alphabeta cells, differentiation stages of TCR gammadelta cells are largely unknown. This report shows that CD1, a known marker of immature TCR alphabeta thymocytes, was expressed on some postnatal TCR gammadelta thymocytes. Only CD1+ TCR gammadelta thymocytes expressed recombination-activating gene-1 mRNA, and they were shown to differentiate into CD1- TCR gammadelta thymocytes. Functionally, sorted CD1- TCR gammadelta thymocytes proliferated in the presence of immobilized anti-CD3 Ab plus exogenous rIL-2 or rIL-15. Interestingly, in contrast to CD1- TCR alphabeta cells, CD1- TCR gammadelta thymocytes also proliferated extensively when cultured with exogenous rIL-2 or rIL-15 alone. FACS analysis as well as reverse transcription-PCR analysis showed that only CD1- TCR gammadelta thymocytes expressed IL-2Rbeta protein and mRNA. The differential expression of maturation markers, such as CD27, CD45RO, and CD45RA, as a function of expression of CD1 was similar in TCR gammadelta and TCR alphabeta thymocytes. An important exception is the expression of CD4 and CD8. Whereas TCR alphabeta thymocytes are mainly CD4-CD8 double positive at the immature CD1+ stage and CD4 or CD8 single positive at the mature CD1- stage, CD1(bright) TCR gammadelta thymocytes all expressed CD4, but only some of them expressed CD8. Some CD1- TCR gammadelta thymocytes also expressed CD8, but were negative for CD4. Collectively, our data clearly show that CD1 is a useful marker to distinguish immature human TCR gammadelta thymocytes from functional mature gammadelta cells based on recombination-activating gene-1 expression, in vitro differentiation, and phenotypic and functional characteristics.

Antigens, CD1↗
PubMed1997

MHC class II molecules are required for initiation of positive selection but not during terminal differentiation of human CD4 single positive thymocytes.

Positive selection of T cell precursors is an MHC dependent, multistep process by which functionally mature CD4+8- helper and CD4-8+ cytotoxic single positive (SP) T cells are generated from immature CD4+8+ double positive (DP) thymocytes. We investigated the requirement for TCR/MHC class II interactions during different stages of positive selection of human CD4 SP thymocytes. We show that sorted CD69- CD4+8+ DP preselection thymocytes cultured in fetal thymus lobes of normal mice were subject to positive selection and differentiated to CD3(high) CD69+, mature CD8 SP, and CD4 SP cells. When cultured in thymus lobes from MHC class II-deficient mice, these precursors failed to develop into mature CD4 SP T cells, indicating that in the hybrid cultures, murine MHC class II molecules are required for the development of mature human CD4 SP T cells. We have previously identified CD4 SP intermediate thymocytes that have received at least some of the signals involved in positive selection, since these cells are CD69+, CD3/TCR(high), and CD8beta- but that are still phenotypically and functionally immature. Here we demonstrate that in contrast to preselection thymocytes, these CD4 SP intermediate thymocytes can give rise to phenotypically mature and functionally CD4 SP progeny both in normal and in MHC class II-deficient thymus lobes. These results suggest that TCR/MHC interactions are required for the initial stages of positive selection, but are not essential during terminal differentiation to functionally mature CD4 SP T cells.

Animals↗