Biomedical subjects

E De Vries

Publications and source records attributed to E De Vries.

11 recordsLinked to original sources

PubMed1992

The CD27 membrane receptor, a lymphocyte-specific member of the nerve growth factor receptor family, gives rise to a soluble form by protein processing that does not involve receptor endocytosis.

CD27 is a transmembrane glycoprotein found exclusively on human T and B lymphocytes. It belongs to a recently identified receptor family, whose members are involved in cell differentiation and survival. This family includes the nerve growth factor receptor, two different types of tumor necrosis factor, receptors the Fas antigen, and the B cell-specific protein CD40. T cell activation via the antigen receptor strongly enhances CD27 membrane expression, suggesting a role for CD27 during T cell differentiation. A soluble form of CD27 (sCD27) is released into the supernatant of activated T cells, and detected in serum and urine of healthy individuals and patients. We have investigated the mechanism underlying the generation of sCD27. One mRNA encodes both the transmembrane receptor and sCD27, as shown by cDNA transfection. In line with this, only one CD27 precursor protein is found, that is processed to the mature receptor by extensive O-linked glycosylation. All newly synthesized protein is rapidly transported to the plasma membrane; no internal pool of mature protein is detectable. The transmembrane form gives rise to sCD27 after arrival at the cell surface, most likely via a proteolytic event, that does not involve receptor internalization.

Antigens, CD↗

PubMed1991

Enhancement of DNA replication by transcription factors NFI and NFIII/Oct-1 depends critically on the positions of their binding sites in the adenovirus origin of replication.

The origin of DNA replication of many human adenoviruses is composed of a highly conserved core origin and an auxiliary region, containing the binding sites for NFI and NFIII/Oct-1. We examined enhancement of DNA replication in vitro by the purified functional DNA-binding domains of NFI (NFI-BD) and NFIII/Oct-1 (the POU domain), using origins in which the positions of the binding sites for these proteins were transposed. Insertion or deletion of two or three base pairs between the core origin and the NFI binding site resulted in a 3-5-fold decrease of stimulation, whereas larger insertions gradually reduced the stimulation further. Mutants in which the NFI binding site was separated approximately one or two helical turns from the core origin by AT-rich sequences could still be stimulated by NFI. In contrast, insertion of two or more base pairs between the NFI and NFIII/Oct-1 binding sites abolished stimulation by NFIII/Oct-1 almost completely. Furthermore, stimulation by this protein was lost when the Ad2 NFIII/Oct-1 binding site was transposed to a position closer to the core origin, destroying the NFI binding site. This shows that the position of the NFIII/Oct-1 binding site is essential for stimulation. Models to explain these position-dependent effects on stimulation are discussed.

Adenoviridae↗

PubMed1989

Alternative molecular form of human T cell-specific antigen CD27 expressed upon T cell activation.

The CD27 membrane antigen is exclusively present on a large subset of human peripheral blood T lymphocytes and on mature thymocytes. Several observations point towards a specific role of this molecule on activated T cells. Upon T cell activation induced via the T cell receptor complex, CD27 expression greatly increases, while addition of anti-CD27 monoclonal antibodies amplifies the proliferative response. Within the CD4+ subset, only CD27+ T cells provide helper activity for B cell differentiation. Interestingly, CD27 expression differs not only quantitatively, but also qualitatively between resting and activated T cells. On resting cells, CD27 is a disulfide-linked homodimer with subunits of 55 kDa molecular mass. Upon activation, also a 55-kDa monomer seems to occur, while in addition a 32-kDa component is found. The relationship between these two proteins has been investigated. The 55-kDa and 32-kDa molecules do not seem to be physically associated. The two CD27 components are structurally highly homologous as determined by two-dimensional mapping of tryptic peptides. They both express the epitopes recognized by anti-CD27 antibodies, indicating that the 32-kDa molecule is also T cell specific. Both 55-kDa and 32-kDa molecules carry N-linked carbohydrate groups. However, they differ in other, not yet specified, post-translational modifications, and do not arise from a common precursor simply by alternative N-glycosylation. The 32-kDa form may be derived by proteolytic processing from the 55-kDa protein, but most likely not from a larger (common) precursor. Alternatively, both molecules may arise from a common gene by alternative mRNA splicing, or be derived from highly homologous genes. The dramatic change in molecular composition of CD27 suggests a newly acquired function for CD27 on activated T cells.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1989

Non-random expression of T cell receptor gamma and delta variable gene segments in functional T lymphocyte clones from human peripheral blood.

Human T cell receptor (TcR) gamma delta displays a variety of protein forms. Disulfide-linked (type 1) or non disulfide-linked (type 2) receptors occur, with gamma chains encoded by the C gamma 1 or the C gamma 2 gene segment, respectively. Exon 2 of C gamma 2 may either be duplicated or triplicated (type 2a or 2b receptors). TcR gamma chains differ in molecular mass and charge between type 1 and type 2 receptors. The delta chains as well as the gamma chains have different structural properties between receptor types. This cannot be due to the use of different C delta gene segments, since the genome encodes only one. To understand the genetic basis of this dichotomy in gamma/delta combinations, rearrangement and expression of V gamma, J gamma, C gamma and V delta gene segments were determined in TcR gamma/delta+ clones derived randomly from peripheral blood of normal donors. Most clones used C gamma 1, a minority C gamma 2. The different protein properties of receptor types could be explained by the non-random expression of V gamma (J gamma) and V delta gene segments. Type 1 receptors preferentially used gamma chains encoded by the V gamma 9 and J gamma 1.2 gene segments together with delta chains encoded by V delta 2. In type 2a receptors, V gamma 9 was not predominant; often other V gamma gene segments were employed, but then in high frequency in coordination with V delta 1. Reactivity of the clones with monoclonal antibodies anti-Ti gamma A, BB3 and delta-TCS-1 correlated with the expression of the V gamma 9, V delta 2 and V delta 1 gene segments, respectively. Therefore, V gamma and V delta use in TcR gamma/delta+ cells from peripheral blood of eight healthy individuals, including the two donors of the clones, could be determined tentatively by double immunofluorescence. Indeed, the V gamma 9-V delta 2 combination was predominant, while the V gamma 9-V delta 1 and particularly the V gamma 9-"V delta other" combination was rare. These data indicate that the TcR gamma delta repertoire in peripheral blood of normal individuals is largely dependent on junctional diversity and suggest that selection of receptors occurs.

Antibodies, Monoclonal↗

PubMed1986

Electronmicroscopical observations on monocyte-lymphocyte interactions upon stimulation with pokeweed mitogen latex conjugate.

In this study we report on the preparation and application of pokeweed mitogen (PWM) conjugated to latex particles. This conjugate (PWM-latex) was prepared by incubation of PWM with latex particles in the presence of glutaraldehyde. The effect of the addition of PWM-latex to human peripheral blood mononuclear cells (PBMC) was fully comparable to the addition of PWM alone i.e. differentiation of lymphocytes into blast cells followed by proliferation of these blast cells as measured by DNA synthesis and total cell number. Electronmicroscopically PWM-latex was found to be taken up by monocytes within the first 24 h after addition. Although no direct interaction could be observed between PWM-latex and lymphocytes, the latter were found to differentiate into blast cells. Due to interactions of these blast cells with latex-containing monocytes, latex particles were obviously released from the phagocytes and close contacts between latex particles and blast cells were regularly seen. In addition, it was found that blast cells of T cell origin, as judged by their positive reaction with anti-T cell monoclonal antibodies, had taken up latex particles. Based on enzyme-cytochemical, functional and light microscopical studies, monocytes could not be detected in the PWM-latex-driven PBMC stimulation after 6 days. At the electronmicroscopical level evidence was found that the inability to demonstrate macrophages could be due to the release of the lysosomal enzyme content and of parts of the cytoplasm.

Cell Communication↗

PubMed1984

Initiation of transcription in yeast mitochondria: analysis of origins of replication and of genes coding for a messenger RNA and a transfer RNA.

The initiation of transcription of the yeast mitochondrial genes coding for subunit I of cytochrome c oxidase (COX1) and for tRNA1Thr has been examined. COX1 messenger RNA synthesis is initiated in a conserved nonanucleotide sequence (ATATAAGTA) which we have previously found immediately upstream of ribosomal RNA genes at positions at which RNA synthesis starts. The 5'-end of the precursor of tRNA1Thr is located in a variant nonanucleotide motif (TTATAAGTA), which may be characteristic for tRNA genes. Using a partially purified fraction of mtRNA polymerase, we demonstrate that RNA synthesis is precisely initiated in vitro in nonanucleotide sequences preceding both ribosomal RNA-, tRNA- and messenger RNA-encoding genes and origins of replication.

Base Sequence↗

PubMed1984

Processing of yeast mitochondrial messenger RNAs at a conserved dodecamer sequence.

The yeast mitochondrial genes coding for cytochrome c oxidase subunit I ( COX1 ) and the ATPase subunits 8 and 6 are organized in one transcription unit. Precise mapping of RNA termini with S1 nuclease and primer extension analysis shows that the 3' end of the COX1 mRNA and the 5' end of the ATPase precursor RNA are juxtaposed within a conserved dodecamer sequence (5'- AAUAAUAUUCUU -3'). Sequence comparison reveals that this motif is present downstream of nearly all protein-encoding genes, including extragenic unassigned reading frames ( URFs ) and two URFs located within introns. Also the 3' terminus of an RNA species derived from the URF -containing intron of the large rRNA gene maps within such a dodecamer sequence. It is likely, therefore, that this motif serves as a processing point in the generation of mature mRNA. From a comparison of the various transcription units, we infer that RNAs that originate from an endonucleolytic cleavage at this sequence have stable 3' termini, while further processing of the 5' ends occurs. The efficiency of the initial cleavage varies between the different positions at which the motif is present.

Adenosine Triphosphatases↗

PubMed1984

C3 receptors on granulocytes from patients with rheumatoid arthritis and Felty's syndrome.

The expression of receptors for the third component of complement (C3R) on polymorphonuclear cells (PMN) from patients with rheumatoid arthritis (RA) or Felty's syndrome (FS) and healthy controls (HC) was studied by means of a rosetting technique using ox erythrocytes coated with rabbit IgM and mouse complement. The percentage of rosette forming PMN (RF-PMN) was found to be increased in patients with FS (59%) and patients with RA (47%) compared to HC (18%), when measured directly after cold isolation of PMN. Incubation at 37 degrees C of cold isolated cells increased the percentage of RF-PMN in all three groups, although the values were significantly higher during the first 45 min of incubation in both patient groups. When incubated with serum from patients with FS at 37 degrees C, cold isolated donor PMN formed significantly more rosettes than after incubation with donor serum. This increase was shown to be due to the presence of circulating immune complexes in the patient sera and could be mimicked by incubating donor PMN with aggregated human IgG. As a result of these experiments it was demonstrated that the increased percentages of PMN with C3R in patients with FS or RA are most likely caused by a previous in vivo activation of PMN by immune complexes. The possible effect of such an increase in C3R expression in relation to PMN function in these patients is discussed.

Antigen-Antibody Complex↗

PubMed1978

PH-dependent behavior of erythrocyte membrane elevations. II Occurrence in moderate acidemic and alkalemic conditions.

Changes of the number of red cell membrane elevations revealed by freeze-etch electron microscopy are pH-dependent in vitro and in vivo. In healthy volunteers a decrease of the number of red cell surfaces with elevations was observed under moderate acidemic and alkalemic conditions. These changes were different in patients with Huntington's chorea and affective psychotic disorders. Elevations of the red cell membrane with the same diameter can be demonstrated in ultrathin sections, if sodium azide is added during the fixation procedure.

Erythrocyte Membrane↗

PubMed1978

pH-dependent behaviour of erythrocyte membrane elevations.

Freeze-etch electron microscopy of human erythrocytes from heparinized normal blood reveals membrane elevations. These elevations disappear at low pH values and reappear under normal pH conditions in vitro, both in the absence and the presence of plasma. This pH-dependent behaviour is discussed as an intrinsic membrane event.

Anticoagulants↗

PubMedDate not supplied

Concentration dependency of cyclosporin and chloroquine as inhibitors of cell proliferation and immunoglobulin production upon mitogen stimulation of mononuclear cells.

The effects of the drugs cyclosporin (Cs) and chloroquine (Chl) on the pokeweed mitogen (PWM)-induced immunoglobulin (Ig) production of peripheral blood mononuclear cells (PBMC) of blood donors, were investigated. A significant inhibition of the Ig production was found at concentrations of 0.001-0.025 microgram Cs/ml and 0.1-2.5 microgram Chl/ml of culture medium respectively, while no effect was found on cell proliferation at these concentrations. The combination of various concentrations of Cs with a constant amount of Chl (0.5 microgram/ml) and various concentrations of Chl with a constant amount of Cs (0.005 microgram/ml culture medium), resulted in a reduction of the Ig content in supernatants which was not different from the calculated sum of the effects of the individual drugs at the respective concentrations. It was concluded that both drugs exerted an effect on the PWM-driven stimulation of PBMC, depending on the concentrations used, which might be of interest in the treatment of rheumatoid arthritis.

Arthritis, Rheumatoid↗