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R Wen

Publications and source records attributed to R Wen.

At least 37 records · Page 2Linked to original sources
PubMed1997

The conventional CD4+ T cell response to staphylococcal enterotoxin B is modified by its superantigenic activity.

Because of the massive cytokine response elicited by superantigen exposure, it has been suggested that superantigens may act as adjuvants to boost conventional antigen responses. However, most previous studies have shown that in vivo exposure to superantigen suppressed subsequent T cell responses. Here we analyzed the effect of the superantigen Staphylococcal enterotoxin B (SEB) on a concurrent CD4(+) immune response to a conventional antigen, an I-Ab-restricted epitope derived from the same protein (SEB127-142). Heat-inactivated SEB, which had lost all superantigenic activity, was capable of eliciting a strong CD4(+) proliferative T cell response to SEB127-142. In contrast, native SEB was relatively nonimmunogenic, even when administered in association with complete Freund's adjuvant. High doses of native SEB coadministered with heat-inactivated SEB had no effect on the peptide response. However, low doses of native SEB were able to strongly enhance the ability of inactive SEB to prime CD4(+) T cells to SEB127-142. Thus, SEB is not always immunosuppressive, and low doses may actually enhance a concurrent immune response. Also, the contribution of Vbeta8(+)/CD4(+) T cells to peptide reactivity was not affected by the presence of low doses of native SEB, suggesting that the enhanced reactivity was not a Vbeta-specific effect of SEB, but was cytokine-mediated.

Adjuvants, Immunologic↗
PubMed1997

Carboxy-terminal residues of major histocompatibility complex class II-associated peptides control the presentation of the bacterial superantigen toxic shock syndrome toxin-1 to T cells.

Previous studies have shown that the presentation of some bacterial superantigens by major histocompatibility complex (MHC) class II molecules is strongly influenced by class II-associated peptides. For example, presentation of the toxic shock syndrome toxin-1 (TSST-1) superantigen by antigen-processing-defective T2-I-Ab cells (which expresses I-Ab that is either empty or associated with invariant chain-derived peptides) can be strongly enhanced by some, but not other, I-Ab-binding peptides. Here we investigate the contribution of I-Ab-associated peptides in the presentation of TSST-1 to T cells. The data show that overlapping peptides expressing the same core I-Ab-restricted epitope, but with various N and C termini, can differ profoundly in their ability to promote TSST-1 presentation to T cells. Analysis of altered and truncated peptides indicates that residues at the C-terminal end of the peptide have a dramatic effect on TSST-1 presentation. This effect does not involve a cognate interaction between the peptide and the TSST-1 molecule, but appears to depend on the length of the C-terminal region. These data are consistent with crystallographic studies suggesting that TSST-1 may interact with the C-terminal residues of MHC class II-associated peptides. We also examined the capacity of naturally processed peptides to promote TSST-1 binding using a superantigen blocking assay. The data demonstrated that a naturally processed epitope is dominated by peptides that do not promote strong TSST-1 binding to I-Ab. Taken together, these data suggest that TSST-1 binding to MHC class II molecules is controlled by the C-terminal residues of the associated peptide, and that many naturally processed peptide/class II complexes do not present TSST-1 to T cells. Thus, the peptide dependence of TSST-1 binding to class II molecules may significantly reduce the capacity of TSST-1 to stimulate T cells.

Amino Acid Sequence↗
PubMed1997

Mechanical injury increases bFGF and CNTF mRNA expression in the mouse retina.

We characterized the survival-factor response of the normal mouse retina to mechanical injury by examining the expression of mRNAs for basic fibroblast growth factor (bFGF), ciliary neurotrophic factor (CNTF), and their receptors, FGF receptor-1 (FGFR-1) and CNTF receptor alpha (CNTFR-alpha). The retina was injured by making an incision through the choroid and retinal pigment epithelium that penetrated the subretinal space of each eye of an adult BALB/c mouse. Retinas were taken 6 hr, 12 hr, 1, 2, 4, 7, 10 and 16 days post-injury. Control animals were without injury. Northern blot analysis was performed to determine bFGF, CNTF and their receptor mRNA levels. A significant increase in bFGF and CNTF mRNAs was observed after injury, along with an increase in glial fibrillary acidic protein (GFAP) expression. More than 2-fold of upregulation of bFGF mRNA was seen as early as 6 hr after injury. This increase reached a maximum of more than 5-fold at day 2 post-injury and then declined slowly, and was still about 2.5-fold of the control level by day 16. Expression of CNTF showed a small increase of about 1.6-fold at 6 hr after injury. The upregulation reached a peak level of about 2.7-fold at day 4 after injury, then declined to control level by day 16. There was only a very small increase in FGFR-1 at 6, 12 and 24 hr after injury, and no significant increases in FGFR-1 at time points longer than 1 day post-injury. Expression of GFAP followed a time course similar to that of bFGF. We conclude that mechanical injury induces bFGF, CNTF, and GFAP expression in the mouse retina with time courses similar to the upregulation of these molecules in rat retina. Compared to the upregulation in rat retina, however, the injury-induced upregulation of bFGF and GFAP is much less in the mouse retina. In addition, there was only a very small induction of FGFR-1 expression in the mouse retina. These findings may explain, at least in part, the lack of injury-induced photoreceptor protection in the mouse retina.

Animals↗
PubMed1997

Induction of basic fibroblast growth factor mRNA by basic fibroblast growth factor in Müller cells.

PURPOSE: To investigate the induction of basic fibroblast growth factor (bFGF) gene expression in cultured rat Müller cells by bFGF and to study the mechanism of induction. METHODS: Müller cells from 1- to 3-day-old Sprague-Dawley rats were isolated and cultured with Dulbecco's modified Eagle's medium with 10% fetal calf serum. Cultured cells were identified by immunocytochemistry using antibodies against vimentin, carbonic anhydrase II, and glutamine synthetase. Cells of passages 1 through 4 were treated with bFGF, the protein kinase C (PKC) inhibitor, H-7; calphostin C, or the PKC activator, PMA; and protein kinase A (PKA) inhibitor, H-89; as well as the adenylate cylase activator, forskolin; or the adenylate cyclase inhibitor, SQ22536. Northern blot analysis was performed to determine the mRNA expression of bFGF, ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF). RESULTS: Addition of bFGF to culture medium induced bFGF gene expression in a dose- and time-dependent manner. Induction of bFCF mRNA started at a bFGF concentration of 0.1 ng/ml. The bFGF mRNA level was elevated by 2-fold at 1 ng/ml of bFGF, 2.8-fold at 5 ng/ml, and reached a peak of 4-fold at 10 ng/ml and 3.7-fold at 50 ng/ml. At 10 ng/ml of bFGF, induction of bFGF mRNA was observed as early as 2 hours (2-fold) after treatment. The bFGF mRNA level continued to increase to 3.7-fold by 4 hours, and reached a maximum of 4.4-fold by 8 hours. A slow decline of the bFGF mRNA level was observed after 8 hours of bFGF treatment (3.5-fold by 12 hours, and 3-fold by 24 hours). This induction of bFGF gene expression was blocked by PKC inhibitors H-7 (30 microM). The PKC activator PMA (0.1 microM) also upregulated bFGF gene expression, but the effects of bFGF and PMA were not additive. An adenylate cyclase inhibitor, SQ22536 (100 microM), did not inhibit bFGF-induced bFGF gene expression. Although forskolin (5 microM), an adenylate cyclase activator, also upregulated the level of bFGF mRNA, the effects of forskolin and bFGF were additive. In addition, no inhibitory effect on bFGF-induced expression of bFGF mRNA was found using H-89 (1 microM). Exogenous bFGF did not alter the mRNA levels of CNTF and BDNF. CONCLUSIONS: These results indicate that bFGF induces bFGF gene expression in cultured rat Müller cells through PKC activation. The authors' findings raise the possibility that Müller cells in vivo also respond to available bFGF (for example, that released from the endogenous reservoirs in the case of injury) or to exogenous bFGF by producing more bFGF, which could in turn promote photoreceptor survival.

Animals↗
PubMed1996

Alpha 2-adrenergic agonists induce basic fibroblast growth factor expression in photoreceptors in vivo and ameliorate light damage.

We observed an induction of basic fibroblast growth factor (bFGF) mRNA in the rat retina after systemic administration of the alpha 2-adrenergic agonists xylazine and clonidine. A single injection of xylazine or clonidine transiently increased bFGF mRNA. Preinjection of yohimbine, an alpha 2-adrenergic antagonist, completely inhibited this increase. Higher dosage of yohimbine inhibited the baseline expression of bFGF. Of particular interest is the finding that the induced bFGF expression occurred almost exclusively in the inner segment region of photoreceptors. No increase in bFGF mRNA was found in the brain after either xylazine or clonidine injection. Xylazine or clonidine given systemically before and during constant light exposure also reduces photoreceptor degeneration in albino rats. These results indicate that regulation of bFGF expression in photoreceptors is unique in the CNS and suggest that endogenous bFGF promotes photoreceptor survival.

Adrenergic alpha-Agonists↗
PubMed1996

Quantitative analysis of polymerase chain reaction products by dot blot.

Quantitative analysis of polymerase chain reaction (PCR) products is usually accomplished by gel electrophoresis and Southern blotting. We have developed an alternative technique that allows PCR products to be directly quantitated from unfractionated samples. The PCR was used to amplify genomic (endogenous) DNA sequences (actin) and exogenous DNA (herpes simplex virus-1 (HSV-1) ribonucleotide reductase) isolated from the trigeminal ganglia of rabbits to demonstrate the dot blot method of PCR product analysis. Two primer pairs (actin and ribonucleotide reductase) were coamplified, resulting in two different PCR products. Duplicate aliquots of the PCR products were applied to separate nylon membranes and hybridized with 32P-labeled oligonucleotide probes. Each radioactive probe was specific for target (HSV-1 DNA) or control (actin DNA) products. Quantitation using a laser scanning PhosphorImager and ImageQuant software demonstrated that the dot blot method can be used to rapidly analyze a large number of PCR samples.

Animals↗
PubMed1996

Major histocompatibility complex class II-associated peptides control the presentation of bacterial superantigens to T cells.

Recent studies have shown that only a subset of major histocompatibility complex (MHC) class II molecules are able to present bacterial superantigens to T cells, leading to the suggestion that class-II associated peptides may influence superantigen presentation. Here, we have assessed the potential role of peptides on superantigen presentation by (a) analyzing the ability of superantigens to block peptide-specific T cell responses and (b) analyzing the ability of individual peptides to promote superantigen presentation on I-Ab-expressing T2 cells that have a quantitative defect in antigen processing. A series of peptides is described that specifically promote either toxic shock syndrome toxin (TSST) 1 or staphylococcal enterotoxin A (SEA) presentation. Whereas some peptides promoted the presentation of TSST-1 (almost 5,000-fold in the case of one peptide), other peptides promoted the presentation of SEA. These data demonstrate that MHC class II-associated peptides differentially influence the presentation of bacterial superantigens to T cells.

Amino Acid Sequence↗
PubMed1996

Quantitation of herpes simplex virus type 1 DNA and latency-associated transcripts in rabbit trigeminal ganglia demonstrates a stable reservoir of viral nucleic acids during latency.

In this investigation we determined the dynamics of herpes simplex virus type 1 (HSV-1) DNA and latency-associated transcripts (LAT) in the latently infected rabbit trigeminal ganglion. Rabbit eyes were infected with either the McKrae strain or the l7Syn+ strain of HSV-1. Rabbits were sacrificed between 5 and 360 days after infection and their trigeminal ganglia were analyzed for the number of HSV DNA genomes and the number of neuronal cells expressing LAT. There was no statistically significant change in the number of HSV genomes or the number of neuronal cells expressing LAT in these ganglia between 20 and 360 days after infection. For both strains, the amount of HSV DNA averaged 16.8 genomes per 100 cells, and 9.2% of the neurons expressed LAT. There were 17 to 34 HSV genomes per LAT-expressing neuronal cell. The number of LAT-expressing neurons did not change over the 360 days. Spontaneous reactivation (HSV-1 recovery in tear film) and recurrence (HSV-1-specific epithelial lesions) occurred during the period of this study; however, these events did not alter the quantity of HSV-1 DNA or the number of LAT-expressing cells. These results suggest that after the latent infection is established, the viral DNA in the ganglia does not replicate to any measurable extent over long periods of latency, since no significant change in the number of HSV genomes occurs. The results also suggest that only a very small number of latently infected neuronal cells are needed to produce infectious HSV-1 during reactivation.

Actins↗
PubMed1996

[Level and significance of the soluble interleukin-2 receptor expression in serum of patients with bladder cancer].

The results of a dynamic study of the soluble interleukin-2 receptor (SIL-2R) expression, interleukin-2 (IL-2) production and natural killer cell factor (NKCF) activity before and after operation in 24 bladder carcinoma patients were reported. The SIL-2R expression level in the patients was significantly higher, the IL-2 production and NKCF activity were remarkably lower than those of controls. Furthermore, the higher the stage of the tumor, the higher the level of the SIL-2R. There was a period of immune suppression after operation. The results suggest that the changes of the SIL-2R expression level, IL-2 production and NKCF activity are closely related to the prognosis of patients with bladder carcinoma.

Aged↗
PubMed1996

[Soluble interleukin-2 receptor in patients with urinary bladder cancer].

Soluble interleukin-2 receptor (sIL-2R) levels in the serum and the effect of the sIL-2R on the natural killer cell factor (NKCF) activity were studied in 31 patients with transitional cell cancer of the urinary bladder. The results showed that serum levels of sIL-2R in the patients were significantly higher than those of controls. sIL-2R level correlated with the stage of the disease. Furthermore, sIL-2R was able to suppress NKCF activity. The results suggest that the sIL-2R may reflect the status of anti-tumor immunity.

Aged↗
PubMed1995

Variable influence of MHC polymorphism on the recognition of bacterial superantigens by T cells.

Superantigen recognition by some T cells is strongly influenced by polymorphic residues of the MHC class II molecule, suggesting that the TCR contacts the class II molecule during superantigen engagement. However, the degree of MHC preference varies with V beta expression. For example, the recognition of staphylococcal enterotoxin B (SEB) by murine V beta 14+ T cell hybridomas is strongly influenced by MHC polymorphism, whereas the recognition of SEB by V beta 8.2+ hybridomas appears to be independent of MHC polymorphism. One possible explanation for this difference is that V beta 14+ TCR may have a lower avidity for SEB such that the stability of the TCR/SEB/MHC complex is more strongly influenced by potential TCR/MHC interactions. To investigate this possibility, we examined the MHC preference of SEB recognition by murine V beta 8.2+/CD4+ T cell hybridomas in which we altered the strength of SEB recognition. First, we compared the recognition of wild-type SEB and mutant SEB, which only weakly activates T cells. Second, we compared recognition of SEB presented by I-E and I-A molecules, which differ in their affinity for SEB. In both cases, the degree of MHC preference was significantly increased when the strength of SEB recognition was reduced. Furthermore, we used mutant MHC class II molecules to show that the degree of MHC preference was controlled by residues of the class II molecule predicted to interact with the TCR during SEB recognition. Taken together, these data support the idea that there is a TCR/MHC interaction during SEB recognition, and the influence of this interaction varies with the overall avidity of the TCR/SEB/MHC complex.

Animals↗
PubMed1995

Injury-induced upregulation of bFGF and CNTF mRNAS in the rat retina.

Focal mechanical injury to the retina has been shown to slow or prevent photoreceptor degeneration near the lesion site in two animal models of retinal degeneration, inherited retinal dystrophy in the Royal College of Surgeons (RCS) and light damage in albino rats. Thus, when injured, the rat retina activates a self-protective mechanism to minimize damage. To identify injury responsive factors and cells, we examined the mRNAs for the following factors and some of their receptors: basic and acidic fibroblast growth factors (bFGF, aFGF) and FGF receptor-1 (FGFR1); ciliary neurotrophic factor (CNTF) and CNTF receptor alpha (CNTFR alpha); brain-derived neurotrophic factor (BDNF) and its receptor trkB; and insulin-like growth factor-1 (IGF-1) and IGFR-1 receptor (IGF-1R). After a single mechanical lesion to the subretinal space and retina, there was a substantial increase in bFGF and CNTF expression that persisted for the entire 10 d period of study. The increase in bFGF mRNA after injury was prompt and great in amplitude, while the elevation of CNTF mRNA was relatively slower. In addition, there was a transient increase in FGFR1 mRNA. In situ hybridizations showed that the elevation of bFGF and CNTF was localized to the vicinity of the lesion. The expression of GFAP (glial fibrillary acidic protein) mRNA also increased in response to injury. These findings strongly suggest that increases in endogenous bFGF and/or CNTF play key roles in injury-induced photoreceptor rescue.

Animals↗
PubMed1994

Expression of a tetrodotoxin-sensitive Na+ current in cultured human retinal pigment epithelial cells.

We observed a tetrodotoxin (TTX)-sensitive Na+ current in cultured fetal and adult cells of the human retinal pigment epithelium (RPE), but not in any freshly isolated fetal (n = 54) or adult (n = 47) cells, using the whole-cell version of the patch-clamp technique. A similar current was found in cultured, but not in freshly isolated, adult monkey RPE cells. The rapid activation and inactivation of this current resembled that of the voltage-dependent Na+ current of excitable cells. The voltage dependence of inactivation followed a Boltzmann function with half-maximal inactivation at -52.1 +/- 4.8 mV (n = 9), thus classifying this current as 'neuronal' in type. Recovery from inactivation followed a single exponential function with a time constant of 12.0 +/- 1.4 ms (n = 5) at -100 mV. The current was very sensitive to the Na+ channel blocker TTX, with a half-inhibition concentration of 1.87 +/- 0.37 nM (n = 5). Of special interest are the findings that current density was high when cells were rapidly proliferating and had lost their melanin pigment, and that the density declined after the cells reached confluence and repigmented. This pattern of current expression was consistently found in cells cultured with three different protocols, including a serum-free medium, indicating that serum was not necessary for its expression. We hypothesize that expression of this Na+ current in culture is regulated by an intrinsic programme related to cell differentiation. It may represent a tendency of proliferating RPE cells to dedifferentiate towards a more embryonic and neuroepithelial phenotype. Similar expression of Na+ current might occur in vivo when RPE cells proliferate, as in wounding.

Animals↗
PubMed1993

Major histocompatibility complex-specific recognition of Mls-1 is mediated by multiple elements of the T cell receptor.

We have recently shown that recognition of the mouse mammary tumor virus 9-associated superantigen (vSAG-9) by murine V beta 17+ T cells is strongly influenced by the major histocompatibility complex (MHC) class II haplotype of the presenting cells, resulting in a form of MHC-restricted recognition. This finding was unexpected, because T cell recognition of another well-characterized retroviral superantigen, minor lymphocyte-stimulating antigen 1 (Mls-1), had been shown to be independent of the MHC haplotype of the presenting cell. To determine whether recognition of vSAG-9 and Mls-1 is fundamentally different, we undertook an extensive analysis of MHC haplotype influences on vSAG-9 and Mls-1 recognition by panels of T cell hybridomas. Our results show that, although most hybridomas recognized Mls-1 regardless of the MHC haplotype of the presenting cells, as previously described by others, some hybridomas exhibited unique patterns of MHC fine specificity. Thus, T cell recognition of vSAG-9 and Mls-1 is not fundamentally different, but the apparent differences can be explained in terms of frequency. The MHC fine specificity of individual Mls-1-reactive hybridomas was influenced by both V beta and non-V beta T cell receptor (TCR) elements. First, the influence of the V beta element was apparent from the observation that V beta 8.2+ hybridomas were significantly more MHC specific in their recognition of Mls-1 than V beta 8.1 hybridomas. Second, a role for the TCR alpha chain was implicated from the distinct patterns of fine specificity of Mls-1 reactivity among a panel of transgenic hybridomas that expressed an identical beta chain (V beta 8.1D beta 2J beta 2.3C beta 2). Sequence analysis revealed that junctional residues of the TCR alpha chain and/or V alpha/J alpha combinations influenced the MHC haplotype fine specificity for Mls-1. Third, D beta J beta influences were implicated, in that the transgenic hybridomas expressed distinctive patterns of Mls-1 fine specificity not represented among V beta 8.1+ nontransgenic hybridomas. The findings that T cell recognition of endogenous superantigen is MHC specific, and that this specificity correlates with non-V beta elements of the TCR, support the hypothesis that there is a direct interaction between the TCR and either polymorphic residues of the MHC class II molecule or haplotype-specific dominant peptides presented by class II.

Animals↗
PubMed1993

Ocular antivirals.

Explore the source record for details and available documents.

Antiviral Agents↗
PubMed1993

Whole-cell K+ currents in fresh and cultured cells of the human and monkey retinal pigment epithelium.

1. Whole-cell potassium currents of freshly isolated human (adult and fetal) and monkey (adult) retinal pigment epithelial (RPE) cells, as well as cultured human and monkey RPE cells were studied using the patch-clamp technique. 2. In freshly isolated adult cells of both species, two currents were observed in the voltage range from -150 to +50 mV: an outwardly rectifying current and an inwardly rectifying current. These currents were also found in cultured cells of both species. 3. The outwardly rectifying current in freshly isolated adult human and monkey cells and some cultured cells was evoked by depolarizing voltage pulses more positive that -30 mV. The current activated with a sigmoidal time course after a brief delay, and was virtually non-inactivating. The conductance associated with the current was half-maximal at -16.4 mV for fresh human cells and -13.5 mV for fresh monkey cells, but was shifted 16.0 and 17.7 mV in the positive direction in cultured human and monkey cells, respectively. The reversal potential of the current in both human and monkey cells matched the potassium equilibrium potential (EK) over a wide range of external potassium concentrations. This current was blocked by 20 mM tetraethylammonium. 4. A membrane current that exhibited inward rectification was observed with hyperpolarizing voltage pulses. The zero-current potential of this current was close to EK. This current was blocked by 2 mM Ba2+ and 2 mM Cs+. In cultured human and monkey cells, but not in fresh cells, this current exhibited an inactivation when voltage pulses were more negative than -120 mV. External Na+ was responsible for the inactivation, as the inactivation was removed in a Na(+)-free solution. 5. Membrane currents in freshly isolated fetal human RPE cells were remarkably different from those in adult cells. A transient outward current resembling the A-type potassium current was observed as the dominant membrane current in freshly isolated fetal human cells. This current activated when voltage pulses were more positive than -30 mV. It inactivated rapidly after reaching a maximal level. Application of 5 mM 4-aminopyridine (4-AP) completely blocked this current. Although this current was never observed in fresh adult cells, it was found in 33% of the cultured adult cells with similar kinetics, ion selectivity, and pharmacological properties. 6. In about 26% of the freshly isolated fetal human cells, a more slowly activating outward current, which resembled the delayed rectifier, was found to co-exist with the transient outward current.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗