Biomedical subjects

R Van Lier

Publications and source records attributed to R Van Lier.

3 recordsLinked to original sources

PubMed1995

Comparison of the response to T-cell activation by integrated HIV-1 and HTLV-1 LTR-lacZ vectors.

Human Jurkat T-cell clones containing stably integrated HIV-1 LTR or HTLV-1 LTR/lacZ vectors were studied to compare the responses of integrated LTRs to T-cell activation. Responses were compared also with those obtained in parallel with Jurkat cells stably expressing lacZ under the control of the cellular enhancer element NF-AT of the IL-2 promoter. Activation induced via the cell surface TCR/CD3 complex or the CD28 receptor elicited responses from the LTR of HIV-1; however, HTLV-1 LTR-directed expression was not observed following triggering of these cell surface pathways. Mitogenic activation by elevation of intracellular calcium (Ca2+) levels along with protein kinase C (PKC) signals was required for optimal expression of the HIV-1 LTR and the NF-AT element; however, increased intracellular Ca2+ was inhibitory to PKC-mediated expression from the HTLV-1 LTR. Time course experiments revealed a sustained PKC-mediated response by the HTLV-1 LTR, which was detectable in the absence of Ca2+ as early as 6 hr following stimulation. In contrast to the HTLV-1 LTR, in time course experiments the HIV-1 LTR responded to stimulation by mitogenic activation of PKC in the absence and presence of Ca2+ and by antiCD3 with lacZ expression beginning as early as 3 hr poststimulation. These results suggest that the HTLV-1 LTR appears to be refractory to several cellular pathways which are upregulatory to the HIV-1 LTR.

Cell Line↗

PubMed1994

Regulation of NF-kappa B nuclear activity in peripheral blood mononuclear cells: role of CD28 antigen.

The NF-kappa B/rel family of transcription factors regulates the expression of a number of genes, including interleukin 2 (IL-2), IL-2 receptor alpha chain (Tac), and others, controlling T lymphocyte activation. The CD28 antigen is involved in regulation of T cell activation. To investigate whether CD28 antigen regulates NF-kappa B factors, we analyzed the effect of an anti-CD28 monoclonal antibody (mAb), CLB-CD28/1, on the nuclear activity of NF-kappa B complexes in resting and CD3-activated peripheral blood mononuclear cells (PBMC) of 11 donors. Cells were incubated with or without the anti-CD3 mAb OKT3 and/or the mAb CLB- CD28/1. Then nuclear extracts were obtained and analyzed for their binding to a 32P-labeled oligonucleotide, corresponding to the NF-kappa B 5'-CAACGGCAGGGGAATCTCCCTCTCCTT-3' consensus sequence in electrophoretic mobility shift assays. PBMC incubated with control medium did not appear to contain significant levels of NF-kappa B nuclear activity. The anti-CD28 mAb did not induce any detectable NF-kappa B nuclear activity in PBMC when used alone, except for two cases. However, cells incubated with the anti-CD3 mAb displayed NF-kappa B nuclear activity in 7 of the 11 cases. The addition of anti-CD28 to the anti-CD3 mAb-stimulated cells enhanced the levels of NF-kappa B activity in eight PBMC, while it did not modify PBMC in one sample and partially inhibited the induction of NF-kappa B in the remaining two samples. The stimulatory effect of anti-CD28 mAb on NF-kappa B nuclear activity was detected also on CD3-stimulated purified T lymphocytes. By analysis with antisera recognizing the p50 and p65 components of the NF-kappa B/rel family, NF-kappa B complexes of CD3+CD28-stimulated PBMC were found to contain both p50 and p65 proteins. An enhanced production of IL-2 was detected in cultures of CD3+CD28-stimulated PBMC. Our results indicate that CD28 triggering can modulate the activity on NF-kappa B nuclear complexes in T lymphocytes stimulated via CD3. Such an effect appeared not to require the presence of accessory cells (AC) or AC-derived cytokines.

Antibodies, Monoclonal↗

PubMed1994

From geons to structure. A note on object representation.

Two models of object perception are compared: recognition by components (RBC), proposed by Biederman, and structural information theory (SIT), initially proposed by Leeuwenberg. According to RBC a complex object is decomposed into predefined elementary objects, called geons. According to SIT, the decomposition is guided by regularities in the object. It is assumed that the simplest of all possible interpretations of any object is perceptually preferred. The comparison deals with two aspects of the models. One is the representation of simple objects--various definitions of object axes are considered. It is shown that the more these definitions account for object regularity and thus the more they agree with SIT, the better the object representations predict object classification. Another topic concerns assumptions underlying the models: the identification of geons is mediated by cues which are supposed to be invariant under varying viewpoints of objects. It is argued that such cues are not based on this invariance but on the regularity of actual objects. The latter conclusion is in line with SIT. An advantage of RBC, however, is that it deals with the perceptual process from stimulus to interpretation, whereas SIT merely concerns the outcome of the process, not the process itself.

Attention↗