Biomedical subjects

J Plum

Publications and source records attributed to J Plum.

At least 73 records · Page 4Linked to original sources

PubMed1997

Osmotic agents and buffers in peritoneal dialysis solution: monocyte cytokine release and in vitro cytotoxicity.

Peritonitis remains a major problem in peritoneal dialysis. The incidence of peritonitis may be reduced by the use of more "biocompatible" peritoneal dialysis solutions that do not impair local host defense mechanisms, such as occurs with conventional lactate-buffered glucose solutions. In the present study, we investigated the use of bicarbonate and lactate as buffer systems and glucose, amino acids, and glucose polymer as osmotic agents on specific cellular functions of isolated fresh blood monocytes in vitro. The bicarbonate-buffered solutions had a physiologic pH (7.0 to 7.6). Lactate-buffered solutions were tested with a pH between 5.5 and 7.3. RPMI 1640 (Roswell Park Memorial Institute, supplied by Biochrom, Berlin, Germany) and phosphate-buffered saline were used as control mediums. The test solutions were incubated with 200,000 monocytes/mL for 45 minutes followed by a 1:1 mix with RPMI 1640 (with supplements) during a 24- or 4-hour tetrazolium bromide test (MTT test) recovery period. Constitutive and lipopolysaccharide (LPS)-stimulated release of interleukin-1beta (IL-1beta) and IL-6 in the supernatants as parameters of cellular host defense and lactate dehydrogenase concentrations and MTT-formazan production as parameters for cell cytotoxicity were measured. Significantly higher IL-6 and IL-1beta release was found in the bicarbonate-buffered solutions, both under basal conditions and after LPS stimulation, compared with the lactate-buffered solutions (LPS stimulation: 1% amino acids/34 mmol/L bicarbonate, IL-1beta: 1,166 +/- 192 pg/mL; 1.5% glucose/34 mmol/L bicarbonate, IL-1beta: 752 +/- 107 pg/mL; 1.5% glucose/35 mmol/L lactate/pH 5.5, IL-1beta: 174 +/- 51 pg/mL). Some of these differences could even be detected in spent dialysate after a 6-hour dwell in continuous ambulatory peritoneal dialysis patients (n = 10). A lower degree of cellular cytotoxicity (lactate dehydrogenase activity) and better-preserved metabolic activity (MTT test) also were found for the bicarbonate-buffered solutions. Amino acids (1%) proved to be comparable to glucose (1.5%) as an osmotic agent at a neutral pH with regard to LPS-stimulated cytokine release and cytotoxicity. The incubation with a glucose polymer solution (7.5% glucose polymer in phosphate-buffered saline, pH 7.3) resulted in a significantly lowered cytokine release (LPS stimulation: IL-1beta, 69 +/- 19 pg/mL) compared with the other solutions with neutral pH (P < 0.01). These results suggest that bicarbonate as a buffer provided better biocompatibility with regard to mononuclear cytokine release and viability compared with lactate. Amino acids and glucose were equivalent to these parameters at a physiologic pH. The glucose polymer solution, however, was associated with a marked depression of cytokine release.

Amino Acids↗

PubMed1997

In vivo and in vitro effects of amino-acid-based and bicarbonate-buffered peritoneal dialysis solutions with regard to peritoneal transport and cytokines/prostanoids dialysate concentrations.

BACKGROUND: Increasing evidence suggests that conventional PD solutions are detrimental to host defence mechanisms of peritoneal cells. We tested a new amino-acid-based and bicarbonate-buffered PD solution under in vivo and in vitro conditions. METHODS: During a prospective, cross-over randomized, intraindividual study 10 CAPD patients were investigated with three different solutions: Amino/Bic, 1% amino acid, 34 mmol/l bicarbonate; Glu/Bic, 1.5% glucose, 34 mmol/l bicarbonate; and Glu/Lac, 1.5% glucose, 35 mmol/l lactate. A PET was performed and transport properties (clearance, D/P ratio, MTAC) were calculated. Prostanoid and cytokine concentrations were measured in serum and the 6 h effluent. Using an in vitro model, mononuclear leukocytes of healthy donors were also incubated with the test fluids. In vivo results. Peritoneal clearance and MTAC of small solutes (creatinine, urea) were not significantly altered by amino acids or bicarbonate. Peritoneal permeability and transperitoneal excretion of higher-weight protein molecules (beta 2-microglobulin, albumin, IgG) were increased with Amino/Bic compared to Glu/Lac (P < 0.05) (D/P ratio albumin: Amino/Bic, 0.027 +/- 0.003; Glu/Bic, 0.023 +/- 0.003; Glu/Lac, 0.022 +/- 0.002). Application of Amino/Bic was accompanied by an increased effluent concentration of Il-6, Il-8, TNF alpha, PGE2, and 6-keto-PGF1a (P < 0.05). Dialysate nitrite/nitrate and cGMP concentrations (as indicators of NO generation) did not differ between the solutions. In vitro results. Both bicarbonate fluids demonstrated a better preservation of the mitochondrial dehydrogenases activity (MTT assay) compared to Glu/ Lac (P < 0.01) (Amino/Bic: 80.6 +/- 3.2%; Glu/Bic: 86.0 +/- 1.8%; Glu/Lac, 64.9 +/- 2.3%, referred to RPMI as control). Constitutive and LPS stimulated release of Il-1 beta and Il-6 was less suppressed with both bicarbonate fluids (P < 0.05) (LPS-stim. Il-6 release: Amino/Bic, 33.0 +/- 6.6%; Glu/Bic, 65.5 +/- 10.3%; Glu/Lac, 1.5 +/- 0.7% referred to RPMI). CONCLUSION: Application of an amino-acid/bicarbonate solution resulted in a small but significant increase in peritoneal permeability. Also increased concentrations of various cytokines/prostanoids were measured in the effluent. According to in vitro testing with mononuclear phagocytes both bicarbonate-buffered fluids were to the same extent less inhibitory to certain cell functions than lactate-buffered solution.

Adult↗

PubMed1997

BSE: can we predict the future?

Prion diseases are transmissible neurodegenerative disorders of humans and animals. The prion protein (PrPc) gene is expressed to some extent in many cell types but principally in neurons. Normal PrPc may contribute in the protection of neurons and are protease sensitive. Abnormal prions consist of a post-translationally modified form of PrP, PrPsc, which is partly protease resistant. PrPsc is a protein with high resistance to inactivation by irradiation, heat and harsh chemical treatments. It is currently proposed that PrPsc is an infectious protein that propagates by inducing the normal PrPc to become the abnormal PrPsc. PrPsc cause transmissible spongiform encephalopathies (TSE), an unusual group of degenerative brain diseases that can be transmitted by inoculation or ingestion of diseased brain or other tissues. The human diseases occur in an inherited, acquired and sporadic forms. Transmission of prion diseases between species is limited by a species barrier, determined in part by the degree of sequence homology between the host PrP and inoculated PrPsc. The epidemic of bovine spongiform encephalopathy (BSE) in the United Kingdom is a new disease that has affected over 160,000 cattle and has presumably arisen from dietary exposure to PrPsc from sheep with scrapie. Until shown otherwise we must assume that oral consumption of infectious BSE protein is a new factor for Creutzfeldt-Jakob (CJD) disease in man. This disease is a new variant of CJD (nvCJD) and has a different clinical picture. Early diagnostic markers to facilitate the diagnosis and screen blood and organ donors are not available. The control of the disease relies on the measures to eradicate the spread of BSE by banning the use of ruminant tissues in ruminant feed and slaughter and rendering procedures to ensure inactivation of prions of all infected animals. The control of nvCJD is based on reduction of exposure to BSE by banning a variety of tissues for consumption. A surveillance worldwide is increased for both BSE and nv-CJD and the WHO update regularly recommendations to limit the risk of transmitting the disease. The extent and size of the nvCJD will depend on different factors among others the dose of infectious material, the route of infection, the genetic susceptibility of the person. Therefore is not possible to predict how important the disease will be.

Animals↗

PubMed1997

BSE: can we predict the future?

Prion diseases are transmissible neurodegenerative disorders of humans and animals. The prion protein (PRPc) gene is expressed to some extent in many cell types but principally in neurons. Normal PrPc may contribute in the protection of neurons and are protease sensitive. Abnormal prions consist of a post-translationally modified form of PrP, PrPsc, which is partly protease resistant. PrPsc is a protein with high resistance to inactivation by irradiation, heat and harsh chemical treatments. It is currently proposed that PrPsc is an infectious protein that propagates by inducing the normal PrPc to become the abnormal PrPsc. PrPsc cause transmissible spongiform encephalopathies (TSE), an unusual group of degenerative brain diseases that can be transmitted by inoculation or ingestion of diseased brain or other tissues. The human diseases occur in an inherited, acquired and sporadic forms. Transmission of prion diseases between species is limited by a species barrier, determined in part by the degree of sequence homology between the host PrPsc and inoculated PrPsc. The epidemic of bovine spongiform encephalopathy (BSE) in the United Kingdom is a new disease that has affected over 160,000 cattle and has presumably arisen from dietary exposure to PrPsc from sheep with scrapie. Until shown otherwise we must assume that oral consumption of infectious BSE protein is a new factor for Creutzfeld-Jakob (CJD) disease in man. This disease is a new variant of CJD (nVCJD) and has a different clinical picture. Early diagnostic markers to facilitate the diagnosis and screen blood and organ donors are not available. The control of the disease relies on the measures to eradicate the spread of BSE by banning the use of ruminant tissues in ruminant feed and slaughter and rendering procedures to ensure inactivation of prions of all infected animals. The control of nVCJD is based on reduction of exposure to BSE by banning a variety of tissues for consumption. A surveillance worldwide is increased for both BSE and nV-CJD and the WHO update regularly recommendations to limit the risk of transmitting the disease. The extent of the size of the nVCJD will depend on different factors among others the dose of infectious material, the route of infection, the genetic susceptibility of the person. Therefore is not possible to predict how important the disease will be.

Animals↗

PubMed1996

Interleukin-7 is a critical growth factor in early human T-cell development.

Highly purified human CD34+ fetal liver stem cells differentiate to mature T cells when seeded in vitro into isolated fetal thymic lobes of severe combined immunodeficient (SCID) mice followed by fetal thymus organ culture (FTOC). Here, this chimeric human-mouse FTOC was used to address the role of interleukin-7 (IL-7) and of the alpha chain of the IL-7 receptor (IL-7R alpha) in early human T-cell development. We report that addition of either the monoclonal antibody (MoAb) M25, which neutralizes both human and mouse IL-7, or the MoAb M21, which recognizes and blocks exclusively the human high-affinity alpha-chain of the IL-7R, results in a profound reduction in human thymic cellularity. Analysis of lymphoid subpopulations indicates that a highly reduced number of cells undergo maturation from CD34+ precursor cells toward CD4+CD3-CD1+ progenitor cells and subsequently toward CD4+CD8+ thymocytes. Our results reveal a critical role for IL-7 during early human thymocyte development, and may explain the absence or highly reduced levels of T cells in patients with X-linked SCID. The molecular defect in these patients has been shown to be a mutation in the gamma chain of the IL-2R. Although this gamma chain is not only present in the IL-2R, but also forms an essential part of other cytokine receptors, including IL-4, IL-7, IL-9, IL-13, and IL-15, the T-cell defect in these patients can be explained by the fact that IL-7 is not able to transduce its signal by the molecular defect of the common gamma (gamma c) chain and that IL-7 is indispensable for T-cell development.

Animals↗

PubMed1996

[Automatic peritoneal dialysis--an adequate therapy option for the treatment of terminal kidney failure. First experiences with a new, pneumatically operated cycler].

OBJECTIVE: To determine whether (1) the recently developed pneumatic cycler for automatic peritoneal dialysis (APD) achieves individually adjustable adequate dialysis efficacy, and (2) changing from continuous ambulatory peritoneal dialysis (CAPD) to APD results in an appropriate increase of dialysis efficacy. PATIENTS AND METHODS: Between July 1994 and August 1995 dialysis treatment for chronic renal failure was performed in 17 patients (four women, 13 men: mean age 42.9 +/- 11.6 years). Ten patients decided primarily on APD, seven changed over from CAPD to APD because of inadequate dialysis efficacy. Adequacy of dialysis was judged by clinical criteria, weekly creatinine clearances (wCcr) and urea levels (urea elimination related to distribution volume [wKT/V]). RESULTS: Mean treatment period with APD was 7.9 +/- 0.3 hours, dialysate volume 19.4 +/- 2.3 1. An ultrafiltration of 1253 +/- 643 ml was achieved. Mean serum creatinine was 13.1 +/- 3.5 mg/dl, mean serum urea-nitrogen 61 +/- 15 mg/dl. wCcr was 78.6 +/- 27.2 1, wKT/V 2.21 +/- 0.33. All patients were adequately dialysed with various forms of APD. In those patients who changed from CAPD the dialysis efficacy, judged by weekly urea-nitrogen elimination, increased by 50% from 1.42 +/- 0.29 to 2.14 +/- 0.20 (P < 0.05). With the pneumatic cycler the different dialysis modes were achieved without problem. CONCLUSION: APD with the new pneumatic cycler provided an adequate and attractive option, from both medical and psychosocial aspects, in the dialysis of patients in chronic renal failure. Changing from CAPD to APD in certain patient groups clearly increased dialysis efficacy so that changing over to haemodialysis can often be avoided.

Adult↗

PubMed1996

Differential effects of interleukin-15 and interleukin-2 on differentiation of bipotential T/natural killer progenitor cells.

Bipotential T/natural killer (NK) progenitor cells are destined to differentiate mainly into T cell receptor (TCR) alpha beta and TCR gamma delta cells in a thymic microenvironment, whereas extrathymically they selectively develop into NK cells. The exact environmental conditions that are required for differentiation into these three leukocyte populations are largely unknown. In this report, we have investigated and compared the effect of interleukin (IL)-15 and IL-2 in this process. The IL-15 receptor is composed of the gamma and beta chains of the IL-2 receptor (IL-2R gamma and IL-2R beta) and of a specific alpha chain (IL-15R alpha). Here, it is shown that IL-15 mRNA is mainly expressed in thymic epithelial stromal cells, whereas IL-2 mRNA is exclusively expressed in thymocytes. IL-2R beta-expressing cells were present in the fetal thymus with a CD25-CD44+Fc gamma R+HSA-/low TCR- phenotype, which is characteristic of progenitor cells. These cells also expressed IL-15R alpha messenger RNA. Sorted IL-2R beta + TCR- cells differentiated into TCR alpha beta and TCR gamma delta cells after transfer to alymphoid thymic lobes, whereas culture of the same sorted cells in cell suspension in the presence of IL-15 resulted in the generation of functional NK cells. This shows that IL-2R beta +TCR- cells of the fetal thymus contain bipotential T/NK progenitors. Addition of low concentrations of IL-15 to fetal thymic organ culture (FTOC) resulted in an increase of all T cell subpopulations. The largest expansion occurred in the TCR gamma delta compartment. In contrast, low concentrations of IL-2 did not result in a higher total cell number and did not induce outgrowth of TCR gamma delta cells. High concentrations of IL-15 blocked TCR alpha beta development and shifted differentiation towards NK cells. Differentiation towards TCR gamma delta cells still proceeded. High concentrations of IL-2 similarly induced development into NK cells, but the cell number was fourfold lower than in IL-15 cultures. Importantly, blocking of IL-2R alpha in IL-2-treated FTOC resulted in a drastic increase in cell number, indicating that IL-2R alpha negatively regulates cell expansion. Collectively, these experiments provide direct evidence that IL-15 and IL-2 differentially affect the differentiation of bipotential T/NK progenitors.

Animals↗

PubMed1996

Thymic development of V gamma 3 cells.

Several characteristics of V gamma 3 cells are clearly different from those of other T cells. V gamma 3 thymocytes mainly originate from fetal precursor cells and only differentiate efficiently in a fetal thymic environment. Evidence is discussed that the early appearance of V gamma 3 cells is probably due to differential gene accessibility which regulates gene rearrangement. Another characteristic of V gamma 3 cells is the canonical sequence of their T-cell receptor (TCR), which seems to be mainly shaped intracellularly by the combination of targeted gene rearrangement, homology-directed recombination and the absence of terminal deoxynucleotidyl transferase, rather than by cellular selection. Contrary to alpha beta cells, V gamma 3 cells express the Fc epsilon RI gamma chain in their TCR complex and other protein tyrosine kinases are important for their thymic differentiation. Also, expression of several cell surface markers is regulated differently on V gamma 3 cells as compared to alpha beta cells. Collectively, these findings show that V gamma 3 cells are a separate lineage of T cells with unique requirements for proper thymic differentiation and survival.

Animals↗

PubMed1996

Isolation of HIV-1 RNA from plasma: evaluation of eight different extraction methods.

The efficacy of eight different methods for the extraction of HIV-1 RNA from plasma was compared. The RNA preparation method that gave the best results by RT-PCR was the one described by Chomczynski and Sacchi (1987, Anal. Biochem. 162, 156-159). This method consists of a guanidine thiocyanate treatment followed by three phenol-chloroform-isoamylalcohol extractions and an ethanol precipitation. The disadvantage of this method is that it is time consuming and less suitable for the extraction of large series of samples. Moreover, due to the large number of procedural steps, there is a greater risk of sample mix-up or contamination. Of the single-step RNA purification methods, good results were obtained with the TRIzol method (Gibco Life Technologies, Paisley, UK) and with the extraction method offered by the NASBA kit (Organon Teknika, Turnhout, Belgium). The above single-step methods are recommended since both are sensitive enough to detect low copy numbers of HIV-RNA in the plasma of asymptomatic patients, and require only 2 h for completion. For most of the methods evaluated the inter-test variability was acceptable (mean variation coefficient between duplicate extraction varied between 17.3 and 47.3%). Inter-laboratory reproducibility was evaluated only for the TRIzol-method and found to be low (mean variation coefficient 63.4).

Evaluation Studies as Topic↗

PubMed1996

Atrial natriuretic peptide in renal transplantation.

Factors related to atrial natriuretic peptide (alpha-ANP) regulation and its potential impact on excretory transplant function were examined in a prospective cohort study of 20 patients with end-stage renal disease over 21 days after allogenic kidney transplantation. Depending on posttransplant graft function, patients were separated into those with primary renal function (PF group, n = 10) and posttransplant acute renal failure (ARF group, n = 10). ANP concentrations were markedly elevated in both PF and ARF immediately after renal transplantation, even when compared with the pretransplant dialysis phase (PF group: 939 +/- 467 pg/ml; ARF group: 648 +/- 306 pg/ml, on 3rd postoperative day; "normals': 72 +/- 35 pg/ml). Whilst ANP levels were persistently elevated in patients with acute renal failure, there was a steady decrease in plasma concentrations in patients with primary renal function (PF: 270 +/- 122 pg/ml on 21st day). ANP concentration correlated with endogenous creatinine clearance (rz = 0.56, p < 0.01, PF group). Moreover, there was a greater correlation between ANP levels and postoperative hydration status, measured as central venous pressure or the difference from predialysis dry weight (rz = 0.79 and rz = 0.74, p < 0.01, PF group). Systolic blood pressure was also positively correlated with ANP concentrations. Together, these factors accounted for a total correlation coefficient of r = 0.87 (p < 0.001) in multiple regression analysis. No significant relation was found between plasma ANP levels and total or fractional sodium excretion or free water clearance. With the restoration of renal function most vasoactive hormones (renin-aldosterone system, catecholamines, vasopressin) decreased towards normal values, whilst ANP plasma concentrations remained elevated.

Adult↗

PubMed1996

Atrial natriuretic peptide, sodium retention, and proteinuria in nephrotic syndrome.

BACKGROUND: Oedema formation in the nephrotic syndrome is primarily due to tubular sodium retention. The pathogenetic role of alpha atrial natriuretic peptide (ANP), a hormonal promoter of natriuresis is unknown. METHODS: In 31 patients (aged 35+/-11 years) with nephrotic syndrome and histopathological evidence of primary glomerulonephritis, we investigated plasma ANP concentration and its influence on renal haemodynamics, natriuresis, and proteinuria (total protein, albumin, IgG excretion). Patients with a compensated treated form of nephrotic syndrome due to primary glomerulonephritis were included in the study. Serum creatinine levels were <=1.4 mg/dl. Diuretic medication was discontinued at least 24 h before the investigation was started. Patients were randomly assigned to ANP infusion (0.005 microg/kg*min; group II, n=15) or received placebo (group III, n=16). Ten healthy subjects (group I) served as normal controls. RESULTS: In normal subjects (group I), ANP caused an increase in natriuresis from 14.5+/-4.2 mmol/h to 26.4+/-11.1 mmol/h (P<0.01). In patients with nephrotic syndrome (group II), baseline sodium excretion of 10.5+/-6.0 mmol/h was increased to 19.6+/-14.8 mmol/h with ANP infusion (P<0.01). No changes were seen in the placebo group III. The absolute increase in ANP induced natriuresis was not significantly different between group I and II. However, plasma ANP levels were significantly higher in patients with nephrotic syndrome (166+/-87 pg/ml vs. 74+/-21 pg/ml, P<0.05) and also reached higher levels after ANP infusion (P<0.01). Therefore, natriuresis was significantly reduced when circulating ANP levels were taken into account (P<0.05). ANP administration resulted in an increase of total protein excretion in patients with the nephrotic syndrome (group II, from 219+/-277 mg/h to 264+/-268 mg/h). Albumin elimination rose from 128+/-151 mg/h to 167+/-170 mg/h (P<0.05) and IgG excretion from 4.91+/-6.67 mg/h to 9.27+/-10.78 mg/h (P<0.05). Healthy subjects also showed a small but significant increase in albuminuria (48+/-38%, P<0.05). Low-dose ANP infusion did not, however, induce any significant alteration in GFR, ERPF and blood pressure. CONCLUSION: ANP plasma concentrations in the steady state are elevated in patients with the nephrotic syndrome. The natriuretic effect of ANP is reduced when referring to circulating ANP plasma levels. Elevated ANP levels enhance urinary protein excretion in the nephrotic syndrome. This is not due to modulation of GFR or FF, but is most probably attributable to increased glomerular permeability.

Adult↗

PubMed1996

Thymic and extrathymic T cell development.

The majority of T cells located in peripheral blood, spleen and lymph nodes are dependent on the thymus for proper differentiation and function. Only a minority of T lymphocytes located in these lymphoid organs is thymic-independent. In contrast, a large number of thymus-independent T cells is present in the gut epithelium. This review deals with phenotypic and functional characteristics of T cell development, summarizes the knowledge on the cytokine requirement in this process and describes positive and negative selection. The differences between thymic-dependent and thymic-independent T cells are emphasized, including selection processes, CD4-CD8 expression and the composition of the CD3 complex.

Animals↗

PubMed1995

Differentiation to T helper cells in the thymus. Gradual acquisition of T helper cell function by CD3+CD4+ cells.

We investigated at which point during thymocyte differentiation functions were acquired that are characteristic for mature Th cells. Differentiation from CD3+CD69-, CD4+CD8+ double-positive (DP) cells to terminally differentiated CD3+, CD4+CD8- single-positive (SP) cells was broken down into six discrete stages that were purified by four-color sorting: CD69-CD3+DP (stage 0), CD69+CD27-DP (stage 1), CD69+CD27-CD4+SP (stage 2), CD27+CD1+CD4+SP (stage 3), CD1-CD45RO+CD4+SP (stage 4), and CD1-CD45RO-CD4+SP cells (stage 5). Phenotypically, these stages seem to describe consecutive steps in differentiation from immature stage 0 to the terminally matured stage 5. Functionally, the capacity to proliferate on IL-2 after stimulation was absent in CD69- stage 0 cells, but was acquired gradually during stages 1 to 4. Clonal expandability and the capacity to respond to stimulation with the production of cytokines were acquired later and rather abruptly by CD1- stage 4 and 5 cells. Activation markers such as CD69 expression and in vivo IL-2 gene transcription came up simultaneously at the DP stage and peaked at stage 3 to 4. These data suggest that functional maturation of Th cells occurs over an extended period in differentiation, stages 1 to 4, and coincides with a gradual increase in activation markers. After completion of functional differentiation, at stage 5, in vivo IL-2 mRNA transcription and CD69 expression are down-regulated, and the cells become functionally resting naive T cells expressing CD45RA+.

Antigens, CD↗

PubMed1995

Characterization of distinct stages during the differentiation of human CD69+CD3+ thymocytes and identification of thymic emigrants.

During thymocyte development, CD69 expression is induced at an early stage of positive selection. To examine the differentiation of human CD69+CD3+ thymocytes, discrete phenotypes were defined by the relative expression of CD69, CD27, CD1, and CD45RA/RO: CD3+CD69- thymocytes were CD27-CD1+CD45RA-/RO+ (phenotype I), whereas the CD3+ CD69+ population could be subdivided into CD27-CD1+CD45RA-/RA+ (phenotype II), CD27+CD1+CD45RA-/RO+ (phenotype III), CD27+CD1-CD45RA-/dull/RO+ (phenotype IV), and CD27+CD1-CD45RA+/ROdull (phenotype V) thymocytes. Phenotype I thymocytes were CD4+CD8 alpha beta + double positive (DP). Phenotype II thymocytes contained DP and CD4+CD8 alpha dullCD8 beta- cells, whereas phenotype III thymocytes were DP and mostly CD4dullCD8 alpha beta+, indicating that CD27 on DP cells may be a marker for CD8-committed cells. Results obtained with SCID-hu mice, transplanted with human fetal thymus and liver, showed that immature human CD69-CD3+ thymocytes were corticosteroid-sensitive, whereas essentially all CD69+CD3+ cells were resistant. During differentiation of one cohort of corticosteroid-resistant CD69+CD3+ thymocytes, phenotype II and III thymocytes, disappeared within a week, whereas the percentage of phenotype IV and especially V thymocytes increased, suggesting that the latter represent the end stages in differentiation. Recent thymic emigrants in SCID-hu mice were identified as CD69-CD27+CD1-CD45RA-/dull/RO+ or CD45RA+/ROdull cells. Because phenotype IV and phenotype V thymocytes rapidly lose CD69 expression in cell culture, these thymocytes are probably the cells that are exported from the thymus. In conclusion, after the acquisition of CD69, thymocyte differentiation appears to continue in an ordered pattern, and cells that eventually leave the thymus are CD69-CD1-CD45RA+ or CD45RA-/dull.

Animals↗

PubMed1995

Influence of TGF-beta on murine thymocyte development in fetal thymus organ culture.

TGF-beta is a multifunctional growth regulator that can either inhibit or stimulate the growth and differentiation of lymphocytes. For several cell types the effect of TGF-beta was found to correlate with the differentiation stage of the cells. We have studied the influence of TGF-beta on the differentiation of murine thymocytes by evaluating the effect of TGF-beta on the generation of thymocyte subpopulations in fetal thymus organ culture. TGF-beta inhibited the growth and differentiation of CD4-CD8- double-negative thymocytes. In the CD4-CD8- double-negative cell population, most cells remained CD44+CD25-, with CD44+CD25+ and CD44-CD25- subpopulations dramatically decreased in cell numbers. The accumulation of cells with a phenotype characteristic of cells in early stage of differentiation suggests a block at very early transition steps. These observations were confirmed in experiments with precursor cells from fetal liver transferred to 2-deoxyguanosine-treated alymphoid thymic lobes, inasmuch as addition of TGF-beta caused a complete inhibition of T cell development. Differentiation into CD4+CD8+ double-positive thymocytes and CD4+ single-positive thymocytes was impaired because these cell numbers were greatly reduced. In contrast, the CD8+ single-positive subpopulation retained normal cell numbers. This CD8+ population had characteristics of a mature subset as the cells expressed CD8 beta and high levels of TCR-alpha beta and CD3. This TCR-alpha beta + cell population was not actively dividing, suggesting that these cells arise de novo by differentiation.

Animals↗

PubMed1995

Stimulation of TCR V gamma 3 cells by gram-negative bacteria.

A distinct feature of most murine TCR-gamma delta cells is that they localize in epithelial tissues that cover the internal and external surface of the body. Therefore, TCR-gamma delta cells have been hypothesized to represent a first line of defense against invading pathogens. In this study, it is shown that TCR V gamma 3 cells are activated to produce cytokines upon interaction with Gram-negative bacteria, whereas Gram-positive bacteria have no effect. Accessory cells are not required. LPS of Gram-negative bacteria is shown to be the stimulating structure for TCR V gamma 3 cells, as the stimulation is inhibited by addition of polymyxin B or anti-LPS Ab and as purified LPS stimulates V gamma 3 T cells. Blocking of the V gamma 3 TCR does not inhibit stimulation by Gram-negative bacteria, whereas suboptimal triggering of the TCR is synergistic. These results demonstrate that LPS is an important stimulus for TCR V gamma 3 cells. This indicates that skin-located V gamma 3 T cells might play a role in the defense against Gram-negative bacteria.

Animals↗

PubMed1995

Cytokine dependence of V gamma 3 thymocytes: mature but not immature V gamma 3 cells require endogenous IL-2 and IL-7 to survive--evidence for cytokine redundancy.

It has previously been described that V gamma 3 cells can proliferate extensively in vitro in the presence of different cytokines. Here, the role of cytokines in the maintenance of V gamma 3 cells in the thymus has been determined. Culture of fetal thymocytes in cell suspension for 24 h showed that, whereas immature TCRlowHSAhigh V gamma 3 cells remained viable, all mature TCRhighHSAlow V gamma 3 cells died. These cells died by apoptosis since protein synthesis was required and flow cytometric analysis as well as DNA gel electrophoresis showed that the DNA was degraded to oligonucleosomal bands. Addition of IL-2, IL-4 or IL-7 to suspension cultures of fetal thymocytes rescued V gamma 3 cells from dying. Addition of IL-1, IL-3, IL-5, IL-6, IL-9, TNF-alpha or IFN-gamma was without effect. Phenotypic analysis showed that the alpha-chain of the IL-2 receptor (IL-2R alpha) was expressed by part of the immature V gamma 3 thymocytes, all mature V gamma 3 cells expressed the beta-chain of the IL-2 receptor (IL-2R beta). Addition of anti-IL-2R beta mAb to fetal thymic organ culture (FTOC) resulted in a moderate reduction of the cell number of mature V gamma 3 thymocytes. Addition of anti-IL-2R alpha, anti-IL-4 or anti-IL-7 mAb had no effect. The cell number of mature V gamma 3 cells was highly reduced when both anti-IL-2R beta and anti-IL-7 mAb were added to FTOC.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Expression and function of Fc receptors in the thymus.

In this review, the expression and function of Fc receptors (FcRs) in the thymus is discussed. In the murine thymus, Fc gamma RII and Fc gamma RIII are expressed on early thymocyte precursors, which can differentiate in both T and NK cells. TCR alpha beta thymocytes that are differentiating along the CD4-CD8 pathway do not express Fc gamma Rs any longer. Mature CD4-CD8 double negative TCR alpha beta and TCR V gamma 3 cells, however, constitutively express Fc gamma RII/III. The generation of gene-deficient mice has shown that neither Fc gamma Rs nor Fc epsilon RII are indispensable for murine thymus-dependent T cell development, whereas normal development of thymus-independent peripheral T cells is dependent on the presence of the FcR gamma chain. In the human thymus, a low number of CD3-CD4-CD8 triple negative cells expresses Fc gamma RIII, but these cells are mainly NK cells. Fc epsilon RII is expressed on human thymic epithelial cells. Although the unaltered thymic development of T cells in FcR-deficient mice argues against a fundamental role of FcRs in this process, recent demonstration of FcR ligands of non-immunoglobulin nature in the thymus indicates that the interaction between FcRs and their ligands in the thymus might influence T cell development.

Animals↗