Search PubMed⌕ Search

Biomedical subjects

R de Jong

Publications and source records attributed to R de Jong.

At least 55 records · Page 3Linked to original sources
PubMed1994

Influence of CD28 co-stimulation on cytokine production is mainly regulated via interleukin-2.

Interaction of CD28 with its ligand B7 plays an important role in the initiation of immune responses. The co-stimulatory signal generated by cross-linking of CD28 molecules results in enhanced T-cell proliferation and augmentation of cytokine production. In particular, mRNA levels of T-helper 1 (Th1)-type cytokines, such as interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) are reported to be strongly increased. We investigated the effect of CD28 co-stimulation on the production of Th2-type cytokines. CD28 mAb induced a strong augmentation of IL-2 secretion in activated T-cell clones. Production of IFN-gamma was also enhanced, but the increase in IL-4 secretion was generally moderate. Augmentation of IL-4 production by CD28 was most pronounced in clones that produced low amounts of IL-2, compared to clones producing high levels of IL-2. It was found that the up-regulation of IL-4 by CD28 co-stimulation was mainly controlled indirectly via an increase of IL-2. Some clones could produce IL-4 in an IL-2-independent manner; in these situations CD28 co-stimulation had no augmenting effect on the production of IL-4. The secretion of IL-4 by peripheral blood CD4+ T cells, that were activated with B7-expressing transfectants, was also found to be dependent on IL-2. Finally, Northern blot analysis confirmed that co-stimulation of CD28 primarily affected IL-2 production, and that inhibition of IL-2/IL-2 receptor interaction abolished the augmenting action of CD28 monoclonal antibody on the production of the Th2-type cytokines IL-4, IL-5 and IL-10 and of the Th1 cytokine IFN-gamma.

Blotting, Northern↗
PubMed1993

DNA-binding specificity of the S8 homeodomain.

The murine S8 homeobox gene is expressed in a mesenchyme-specific pattern in embryos, as well as in mesodermal cell lines. The S8 homeodomain is overall similar to paired type homeodomains, but at position 50, which is crucial for specific DNA recognition, it contains a Gln, as is found in Antennapedia (Antp)-type homeodomains. We determined the DNA-binding specificity of the purified S8 homeodomain by in vitro selection of random oligonucleotides. The resulting 11-bp consensus binding site, ANC/TC/TAATTAA/GC resembles, but subtly differs from, the recognition sequences of Antp-type homeodomains. Equilibrium binding constants of down to 6.0 x 10(-10) M were found for binding of the S8 homeodomain to selected oligonucleotides. Using specific antibodies and an oligonucleotide containing an S8-site, we detected by band-shift two abundant DNA binding activities in mesodermal cell lines that correspond to S8 and two more that correspond to its close relative MHox. These S8 protein forms are differentially expressed in retinoic acid-treated P19 EC cells.

Amino Acid Sequence↗
PubMed1993

Regulation of CD27 expression on subsets of mature T-lymphocytes.

CD27, a lymphocyte-specific member of the TNF/NGF-R family, is expressed on the majority of peripheral blood T cells. Activation of T cells via TCR/CD3 induces high CD27 surface expression and the release of a soluble extracellular part of the molecule. After prolonged activation in vitro, CD27 becomes gradually switched off. There is evidence that also in vivo, CD4+ cells that have persistently been stimulated by Ag, accumulate within the CD45RA-CD27- subset. In addition, an increase of CD27- T cells has been observed under certain immunopathologic conditions and during aging. This study was undertaken to analyze the regulation of CD27 on different T-cell subsets and to determine whether the loss of CD27 expression is an irreversible event and may thereby mark T-cell differentiation. In agreement with earlier findings, all CD4+CD45RA+CD45RO- T cells were found to express CD27, whereas a small fraction of the CD4+CD45RA-CD45RO+ subset lacks the molecule. In contrast, within the CD8+ compartment CD27- subsets were found both in the CD45RA+ and CD45RA- subpopulations. After stimulation with CD3 mAb, both CD27 membrane expression and release was equally up-regulated in CD4+ and CD8+ subpopulations. This stimulus, however, provoked a strikingly predominant up-regulation of membrane CD27 on CD45RO- cells as compared with CD45RA- cells. On CD4+CD45RA-CD27- T cells and long-term grown CD45RA-CD27- TLC, CD27 expression could not be reinduced after stimulation of the TCR/CD3 complex, neither at the protein nor at the mRNA level. Comparison of CD27 expression with its structural homologue FAS/APO-1 showed that down-regulation after prolonged activation is not a general feature of TNF/NGF-R family members. The CD27 ligand was recently identified and was shown to give a co-stimulatory signal to PHA-activated T cells. The restricted up-regulation of CD27 on CD45RA+ cells after T-cell stimulation may point at a discrete role of CD27-CD27 ligand interaction during transition of CD45RO- to CD45RA- T cells. In addition, the CD27 negative phenotype seems a stable reflection of differentiation rather than of activation.

Antigens, CD↗
PubMed1993

Development of human Th1 and Th2 cytokine responses: the cytokine production profile of T cells is dictated by the primary in vitro stimulus.

Regulation of interleukin (IL)-4 production, but not IL-2 production, was found to be quite different in either freshly isolated T cells or T cell clones. Both fresh T cells and T helper 2-like clones produced IL-4 when stimulated with anti-CD2 in combination with anti-CD28. However, whereas T cell clones showed enhanced IL-4 production when phorbol 12-myristate 13-acetate (PMA) was used in addition to anti-CD2 and anti-CD28, IL-4 production by fresh T cells was inhibited by the presence of PMA. Prestimulation of fresh T cells led to the following observations: (a) activation in the absence of PMA led to a reversal of the PMA effect and (b) within 2 days these cells resembled T cell clones in that IL-4 production was no longer inhibited by PMA. When prestimulation was carried out in the presence of PMA, the inhibition of IL-4 production seemed irreversible. Removal of PMA after 3 days did not lead to renewed capability of IL-4 production, whereas IL-2 production was unimpaired. Our data show that the capacity of cultured T cells to produce IL-4 is determined and fixed during the first 2-3 days of stimulation.

Antigens, CD↗
PubMed1993

The homeobox gene S8: mesoderm-specific expression in presomite embryos and in cells cultured in vitro and modulation in differentiating pluripotent cells.

The S8 gene of the mouse contains a paired-like homeobox and is expressed during organogenesis in a complex pattern in mesenchyme. Here we show that S8 is first expressed in extraembryonic mesoderm of primitive streak stage embryos and that it is strongly expressed in mesoderm of early-headfold/neural plate stage embryos. It is, however, absent from the primitive streak and its immediately adjacent areas. Early after initial mesoderm formation, this expression domain defines a specific region of the mesoderm that, to some extent, foreshadows the later S8 expression pattern. The pattern at this stage is roughly complementary to that of the brachyury (T) gene. Expression in cell lines was studied both at the level of RNA and protein. Mesoderm specificity of S8 expression was confirmed in terminally differentiated cell lines. S8 is activated by retinoic acid in certain embryonal carcinoma cells, embryonic stem cells, and neural crest cell lines, and also during spontaneous differentiation in embryonic stem cells.

Animals↗
PubMed1992

Maturation- and differentiation-dependent responsiveness of human CD4+ T helper subsets.

The human CD45R0+ (memory) CD4+ T cell population can be subdivided into a large (82%) CD27+ and a small (18%) CD27- subset. Within the CD45R0+CD27- subset, cells accumulate that have been persistently stimulated by Ag in vivo. As an apparent consequence, TLC with a differentiated functional phenotype, producing either high levels of IFN-gamma (Th1-like), high levels of IL-4 (Th2-like) or high amounts of both these cytokines (here referred to as Thx) can primarily be generated from the CD27- memory CD4+ T cell subset. In this study we examined the requirements for induction of proliferation of distinct CD4+CD45R0+ Th subsets. Immobilized CD3 mAb induced proliferation with comparable magnitude and kinetics in all types of TLC. However, interference with intracellular signaling pathways in this activation system, resulted in a strong inhibition of proliferation in TLC derived from CD27+ cells whereas, in contrast, TLC from CD27- cells were relatively resistant to elevation of [cAMP]i, inhibition of protein kinase C activation and the immunosuppressive effects of cyclosporin A. Stimulation with CD3 mAb in soluble form resulted in Il-4 secretion by Th2-like and Thx-type TLC but did not induce IFN-gamma or Il-2 secretion in any Th subset. Interestingly, Th2-like cells but not Thx-type cells were able to use endogenously produced Il-4 for proliferation. These data demonstrate a differential sensitivity of CD45R0+CD4+ Th subsets for immune activation and suppression, which correlated with their maturation stage, as reflected by CD27 membrane expression, as well as with their effector phenotype.

Antibodies, Monoclonal↗
PubMed1992

DNA-binding activity of the murine homeodomain protein Hox-2.3 produced by a hybrid phage T7/vaccinia virus system.

Homeobox-containing genes encode transcription factors that, via the homeodomain, bind specifically to DNA. To study the DNA-binding properties of the murine homeodomain-containing protein, Hox-2.3, a hybrid expression system was used, combining gene expression by recombinant vaccinia virus (reVV) with bacteriophage T7 transcription. Expression was achieved by co-infecting HeLa cells with two reVVs, one expressing the T7-RNA polymerase-encoding gene directed by the VV promoter, P7.5, and another containing the Hox-2.3 coding sequence under control of a T7 promoter [Fuerst et al., Mol. Cell. Biol. 7 (1987) 2538-2544]. Co-infected HeLa cells produced large amounts of full-length Hox-2.3 protein. Cytoplasmic and nuclear extracts from these cells were used to examine DNA-binding specificity in vitro. reVV-produced Hox-2.3 protein bound to oligos that contained one or several copies of the common homeodomain-binding site, 5'-TCA-ATTAAAT, and to a lesser extent to multiple (TAA) repeats. Using Southwestern blot analysis, no Hox-2.3-binding sites were detected in a region of the Hox-2 cluster containing the Hox-2.3, Hox-2.4 and Hox-2.5 genes.

Animals↗
PubMed1992

Towards a sustainable livestock production in developing countries and the importance of animal health strategy therein.

Livestock and animal health development projects have not always led to substantial increases in animal productivity or in farmers' welfare. Some have even resulted in unsustainable systems, when they were not based on an understanding of (livestock) production systems. The multipurpose functions of livestock and complex relationships between the biological, technical and social components require a systems approach, whereby nutrition, animal health, breeding, biotechnology knowhow, inputs and technologies are used to optimise resource use. The challenge for developed and developing countries is to reverse the current degradation of the environment, and arrive at sustainable increases in crop and livestock production to secure present and future food supplies. For rural development, governments should show long term commitment and political will to support the rural population in development programmes, because smallholders (including women and landless livestock keepers) represent a large labour force in developing countries. Different systems need different approaches. Pastoral systems must focus on effective management of grazing pressure of the rangelands. Communal rangelands management involves not only the development and application of technologies (e.g. feedlots, vaccination campaigns), but also land tenure policies, institutional development, economic return and a reduction in the number of people depending upon livestock. Smallholder mixed farms must aim at intensification of the total production system, in which external inputs are indispensable, but with the emphasis on optimum input-output relationships by reducing resource losses due to poor management. Resource-poor farming systems must aim at the improved management of the various livestock species in backyards and very small farms, and proper packages for cattle, buffaloes, sheep, goats, rabbits and poultry should be developed. Specialised commercial livestock farming systems (poultry, pigs, dairy or meat) can only be sustainable with adequate marketing, supply of quality feed, veterinary services, labour, management and control of pollution. Animal health programmes play a keyrole in the proposed system approach.

Agriculture↗
PubMed1991

A soluble form of the human T cell differentiation antigen CD27 is released after triggering of the TCR/CD3 complex.

The human T cell Ag CD27 belongs to a recently defined family of cell surface receptors, including the nerve growth factor receptor, two distinct tumor necrosis factor receptors, and the B cell specific molecule CD40. On resting T cells, CD27 is a transmembrane homodimer with subunits of 50 to 55 kDa (p55). T cell activation via the TCR/CD3 complex causes a strong enhancement of p55 expression. Concomitantly, an alternative form of the CD27 molecule with a molecular mass of 28 to 32 kDa (p32) appears at the cell surface. With the use of ELISA, we here show that a soluble form of CD27 (sCD27) can be detected in the supernatant of T cells activated with anti-CD3 or combinations of anti-CD2 mAb. Moreover, sCD27 is found in both serum and urine from healthy donors. sCD27, purified from either culture supernatant or urine, has a molecular mass of 28 to 32 kDa and is, according to peptide mapping, structurally homologous to the p55 membrane form of CD27. Quantification of sCD27 levels may be used as a marker for T lymphocyte activation in vivo.

Antigens, CD↗
PubMed1991

Regulation of expression of CD27, a T cell-specific member of a novel family of membrane receptors.

CD27 belongs to a newly defined family of transmembrane R, including the nerve growth factor R, two distinct TNF R and CD40. The function of CD27 is unknown, but on the basis of structural and functional properties, we postulate that it plays a role in the events subsequent to T cell activation, possibly as a cytokine R. We have analyzed the mechanisms underlying the regulation of CD27 protein expression. Membrane expression of CD27 strongly increases after T cell activation via the TCR/CD3 complex or the CD2 molecule. In contrast, direct stimulation of protein kinase C by phorbol esters markedly down-regulates CD27 surface expression. This down-regulation most likely does not result from CD27 phosphorylation, because both anti-CD3 mAb and PMA induce hyperphosphorylation of CD27 on serine residues. Rather, membrane expression seems to be regulated primarily at the RNA level. Stimulation of T cells with anti-CD3 mAb strongly increases steady state CD27 mRNA levels, whereas PMA treatment greatly reduces these transcript levels. Dissection of the TCR/CD3-induced signaling pathways showed that cytoplasmic cAMP as well as Ca2+ concentrations contribute to the increase of CD27 expression. These data indicate that upon Ag-specific T cell stimulation, membrane expression of CD27 is regulated at the RNA level through the joint action of distinct TCR/CD3-associated signaling pathways.

Antibodies, Monoclonal↗
PubMed1991

Human CD8+ T lymphocytes can be divided into CD45RA+ and CD45RO+ cells with different requirements for activation and differentiation.

The functional distinction between CD45RA+ and CD45RO+ cells within the human CD4+ T cell subset is well established. This study was undertaken to investigate whether a similar division can be made within the CD8+ T cell population. A quantitative comparison was made of the requirements for activation and differentiation of CD8+CD45RA+ and CD8+CD45RO+ cells. Stimulation of T lymphocytes with anti-CD3 mAb immobilized at high-density induced strong proliferation and CTL activity in both CD45RA+ and CD45RO+ cells. Suboptimal TCR/CD3 triggering, in contrast, induced substantially higher levels of proliferation and CTL activity in CD8+CD45RO+ cells compared with their CD45RA+ counterparts. Lymphokine secretion (i.e., Il-2 and TNF-alpha) was under any condition more readily induced in CD8+CD45RO+ cells. Markedly, proliferation of both CD8+CD45RA+ and CD8+CD45RO+ T cells initiated by anti-CD3 mAb immobilized at high densities was not inhibited by addition of anti-CD25 mAb, in contrast to proliferation induced by suboptimal anti-CD3 mAb concentrations. These findings show that a functional division between CD45RA+ and CD45RO+ T cells with distinct requirements for activation and differentiation may also be made in the CD8+ subset.

Antigens, CD↗
PubMed1991

Regulation of T-cell differentiation by CD2 and CD28 accessory molecules.

It was analysed to what extent the functional T-cell responses that result from T-cell receptor (TcR)/CD3 triggering differ from responses that are induced after simultaneous ligation of CD2 and CD28 accessory molecules. To allow a quantitative comparison of these activation pathways, purified lymphocytes were stimulated with either graded densities of immobilized anti-CD3 monoclonal antibodies (mAb) or with increasing amounts of anti-CD28 mAb in the presence of a constant concentration of anti-CD2 mAb. Both activation systems were sensitive to the regulatory properties of CD11a/CD18 molecules. T-cell stimulation via CD2/CD28 molecules induced a more potent release of interleukin-2 (IL-2) and more pronounced T helper (Th) cell responses than T-cell stimulation via the TcR/CD3 complex, whereas CD25 expression was more readily initiated after T-cell activation via the TcR/CD3 complex. Optimal Th cell differentiation was detected under conditions of suboptimal receptor occupancy whereas, in contrast, optimal cytolytic T lymphocyte (CTL) differentiation required optimal TcR/CD3 or CD2/CD28 engagement. The findings indicate that T-cell differentiation can be influenced in a qualitative manner by the strength of the activation signal provided, and suggest that antigen-specific T-cell responses might be regulated in a quantitative manner through CD2 and CD28 accessory molecules.

Antigens, CD↗
PubMed1990

99mTc-human immunoglobulin (HIG)--first results of a new agent for the localization of infection and inflammation.

Technetium (99mTc) labelled, polyclonal human immunoglobulin (HIG) is a new agent that detects focal infection and inflammation. This new agent was compared in 40 patients with the accepted standard, namely 111In-oxine-labelled leucocytes. This comparison resulted in a sensitivity of 94% and a specificity of 96% for 99mTc-HIG when 111In-oxine leucocytes were defined as giving the true result. The new agent was shown to localize both sepsis and active inflammatory bowel disease (IBD). There was 100% concordance in the 16 patients with IBD who were imaged with both 99mTc-HIG and 111In-oxine leucocytes. Discordant results were obtained in one case of suspected osteomyelitis, which was false-positive on the 99mTc-HIG scan, and one case of pyrexia of unknown origin when the 99mTc-HIG was false-negative and the 111In-oxine leucocyte scan demonstrated accumulation of tracer in the caecum at 24 h post-injection. Normal distribution for 99mTc-HIG demonstrated activity in the kidneys and bladder and that 50% of the tracer is cleared through the kidneys during the first 24 h post-injection. There were no major or minor side-effects.

Bacterial Infections↗
PubMed1990

Influence of gastro-intestinal nematodes on the productivity of dairy cattle in the wet highlands of Sri Lanka.

To study the response and economics of nematode control in cattle, trials with anthelmintics were carried out in the wet season at New Zealand farm in the highlands of Sri Lanka. Three age groups were used: stall fed yearlings, grazing heifers and lactating cows. Groups were treated with ivermectin or febantel and monitored along with control groups for faecal egg counts, growth and milk production. Treatment reduced the trichostrongylid faecal egg counts in yearlings, heifers and cows for six to 10 weeks, for more than 10 weeks and for 140 days respectively. The growth rate of treated yearlings did not increase significantly while treated heifers did grow significantly faster. Treated cows produced an average of 115 kg more milk over 133 days (P less than 0.05). The economic gains in reducing the age at first service and in terms of milk yield far outweighed the cost of anthelmintics used.

Animals↗
PubMed1988

Transcription of T cell receptor beta-chain genes is controlled by a downstream regulatory element.

To characterize cis-acting elements controlling the expression of T cell receptor beta-chains we generated a number of transgenic mouse lines harboring a rearranged T cell receptor beta-chain with different extensions of 5' and 3' flanking sequences. Transcriptional analysis of transgenic mice carrying these clones showed that sequences located downstream of the polyadenylation signal of the C beta 2 region are indispensable for expression in transgenic mice. The sequences conferring enhancer activity in this fragment were further defined by transient CAT assays. Strong enhancer activity was found to reside in a 550 bp fragment located 5 kb downstream from C beta 2. The nucleotide sequence of this fragment revealed a number of oligonucleotide motifs characteristic for enhancer elements.

Animals↗
PubMed1988

The influence of antihistamines on human performance.

We have studied the effects of three antihistamines on task performance in two separate experiments. Healthy subjects were tested at weekly intervals in a double-blind, Latin square design. In Experiment I the subjects were treated orally with loratadine 10 mg, clemastine 1 mg, terfenadine 60 mg, or placebo. In Experiment II 5 mg diazepam was given orally with each of the four treatments used in Experiment I. In both experiments subjects' performance was evaluated in reaction time and tracking tasks after treatment. In both experiments, the tracking task initially was performed alone and then simultaneously with a continuous memory task; the subject also graded their mental status on visual analogue rating scales. In both experiments task performance was not generally impaired after treatment with loratadine or terfenadine. The concomitant administration of diazepam in Experiment II appeared not to affect subjects' performance. However, clemastine caused a decay in subjects' performance in both Experiments I and II, but only on the tracking task. At the conclusion of both experiments, sleepiness was reported by more subjects when treated with clemastine than when treated with loratadine, terfenadine, or placebo.

Administration, Oral↗
PubMed1988

Use of partial stimulus information in response processing.

We examined the reaction time benefit that is obtained when salient features of the stimulus set and response set correspond. Components of the event-related brain potentials were used to measure the timing of stimulus-related and response-related processes in order to determine the locus of this effect. Of particular importance was the development of a new index of selective response preparation, the corrected motor asymmetry (CMA). We found no evidence for the use of preliminary, partial stimulus information in response preparation. These results suggest that the benefit is located primarily in response selection processes and probably reflects a more efficient algorithm for stimulus-response translation. Also, we found trial-to-trial variability in the duration of response selection to be the major determinant of variability in reaction time, whereas the durations of subsequent response-related processes were relatively invariant. Implications of these results for discrete and continuous models of choice reaction performance are discussed.

Adult↗