Biomedical subjects

Y W He

Publications and source records attributed to Y W He.

At least 19 recordsLinked to original sources

PubMed2000

Down-regulation of the orphan nuclear receptor ROR gamma t is essential for T lymphocyte maturation.

Thymocyte development is a tightly regulated process. CD4+CD8+ double-positive (DP) immature thymocytes exhibit distinct phenotypic features from mature T cells; they express only 10% of surface TCR that are found on mature T cells and do not proliferate and produce IL-2 in response to stimulation. In this report we show that transgenic expression of the orphan nuclear receptor ROR gamma t in mature T cells down-regulates their surface TCR expression. The ROR gamma t transgene inhibits IL-2 production by mature T cells, and this inhibition may be partially due to the inhibitory effect of ROR gamma t on c-Rel transcription. Furthermore, ectopic expression of ROR gamma t inhibits the proliferation of mature and immature T cells. These results, together with its predominant expression in DP thymocytes, suggest that ROR gamma t controls these distinct phenotypic features of DP thymocytes. Our data suggest that down-regulation of ROR gamma t expression in thymocytes is essential for their maturation.

Animals↗

PubMed2000

The role of orphan nuclear receptor in thymocyte differentiation and lymphoid organ development.

T lymphocytes differentiate in the thymus through several phenotypically distinct stages that are tightly regulated by multiple nuclear transcription factors. Immature CD4+CD8+ double positive (DP) thymocytes make up a majority of the population in the thymus, and exhibit several phenotypic features distinct from mature T cells. DP thymocytes express only about 10% of surface TCR that are found on mature T cells and do not proliferate and produce IL-2 in response to stimulation. Several critical events of T lymphocyte maturation such as TCRalpha gene recombination, positive and negative selection, and CD4/CD8 lineage commitment occur around the DP stage. Recent studies from our group and others on the orphan nuclear receptor RORgamma and its thymus-specific isoform RORgammat support a critical role for this nuclear receptor in the regulation of DP thymocyte function. In addition, RORgamma is required for the development of lymph nodes and Peyer's patches.

Animals↗

PubMed1999

High level expression of CD43 inhibits T cell receptor/CD3-mediated apoptosis.

In a screen designed to identify genes that regulate T cell receptor (TCR)/CD3-mediated apoptosis, we found that high level expression of CD43 protected T cell hybridomas from activation-induced cell death. The protection appears to result from its capacity to block Fas-mediated death signals rather than from inhibition of the upregulation of Fas and/or Fas ligand after T cell stimulation. We found that peripheral CD4(+) T cells can be divided into two subsets based on the level of CD43 surface expression. The CD4(+)CD43(low) subset exhibits a naive T cell phenotype, being CD62L(high)CD45RB(high)CD44(low), whereas CD4(+)CD43(high) cells exhibit a memory phenotype, being CD62L(low)CD45RB(low)CD44(high). Recent studies have demonstrated that engagement of TCR and Fas induces naive CD4(+) T cells to undergo apoptosis, and the same treatment enhances the proliferation of memory CD4(+) T cells. We confirm here that peripheral CD4(+)CD43(high) T cells are resistant to TCR/CD3-mediated cell death. These results suggest that the expression levels of CD43 on naive and memory CD4(+) T cells determine their susceptibility to Fas-dependent cell death and that high level expression of CD43 may be used as a marker to define CD4(+) memory T cells. Expression of CD43 provides a novel mechanism by which tumor cells expressing abnormally high levels of CD43 may escape Fas-mediated killing.

Animals↗

PubMed1999

Multiple gamma c-dependent cytokines regulate T-cell development.

Mutations in the common gamma chain (gamma c) of cytokine receptors account for human X-linked severe combined immunodeficiency disease. gamma c contributes to ligand binding and signaling as a component of five cytokine receptors: interleukin-2-receptor (IL-2R), IL-4R, IL-7R, IL-9R and IL-15R. Here, Thomas Malek and colleagues discuss the contribution of individual gamma c-dependent cytokines in both conventional and intraepithelial T-cell development.

Animals↗

PubMed1998

Monoclonal antibodies to the common gamma-chain as cytokine receptor antagonists in vivo: effect on intrathymic and intestinal intraepithelial T lymphocyte development.

Mice lacking a functional gamma c subunit of cytokine receptors exhibit profound defects in the development of multiple lymphoid lineages. To investigate the role of gamma c-dependent cytokines in T cell development, the phenotype of developing T cells was compared in interleukin (IL)-7Ralpha-deficient mice and anti-gamma c mAb-treated chimeric mice reconstituted with adult bone marrow cells or subsets of pro-T cells. These studies indicate that gamma c contributes to T cell development at multiple stages of pro-T cell maturation and that IL-7/IL-7R is the primary cytokine for thymic-dependent T cell development. However, our data also implicate other gamma c-dependent cytokines during thymic T cell development. By contrast, substantial intestinal intraepithelial lymphocytes (IEL) development was observed in the intestinal intraepithelium in both types of mice. Analysis of IL-7Ralpha-deficient mice indicates that the IL-7/IL-7R system is critical only for the development of TCR gammadelta+ IEL. However, the inhibitory activity of the anti-deltac mAb in the chimeric mouse model suggests that additional gamma cutilizing cytokines regulate the development of the remaining subsets of IEL.

Animals↗

PubMed1998

Correlating notch signaling with thymocyte maturation.

The Notch receptor and its ligands are involved in many developmental processes. They are highly expressed in the thymus and have been implicated in the CD4 versus CD8 lineage decision. We identified the constitutively active intracellular fragment of murine Notch-1 as capable of rendering thymomas resistant to glucocorticoid-induced apoptosis. This effect was confirmed in other T cell lines and in CD4+ CD8+ DP thymocytes. Activation of the Notch signaling pathway also upregulated a number of other markers that, like steroid resistance, correlate with DP maturation into both the CD4 and CD8 lineages. These results suggest that Notch signaling is critically involved in the maturation of DP thymocytes into both CD4+ and CD8+ SP thymocytes.

Animals↗

PubMed1998

RORgamma t, a novel isoform of an orphan receptor, negatively regulates Fas ligand expression and IL-2 production in T cells.

We have identified RORgamma t, a novel, thymus-specific isoform of the orphan nuclear receptor RORgamma that is expressed predominantly in CD4+ CD8+ double-positive thymocytes. Ectopic expression of RORgamma t protects T cell hybridomas from activation-induced cell death by inhibiting the upregulation of Fas ligand. Following hybridoma stimulation, RORgamma t also inhibits IL-2 production but does not affect the induction of Nur-77 and Egr-3 nor the upregulation of CD69. Both the ligand-binding and DNA-binding domains of RORgamma t are required for this effect. We propose that the role of RORgamma t expression in immature thymocytes is to inhibit Fas ligand expression and cytokine secretion following engagement of their TCR during positive or negative selection.

Amino Acid Sequence↗

PubMed1998

The structure and function of gamma c-dependent cytokines and receptors: regulation of T lymphocyte development and homeostasis.

Five cytokines, IL-2, IL-4, IL-7, IL-9, and IL-15, form one group that is characterized by utilizing the common gamma chain (gamma c) as a receptor subunit. Examination of the phenotype of various cytokine or cytokine receptor "knockout" mice demonstrates that these cytokines are critical for normal lymphocyte development and subsequent functional activity of the peripheral immune compartment. This review summarizes the structural and functional properties of each of these five cytokines and their receptors, including the known redundant pathways for each cytokine or receptor. The contribution of these cytokines and receptors will then be considered in detail with respect to regulation of T lymphocyte development and homeostasis of the peripheral T cell compartment.

Animals↗

PubMed1997

The common gamma-chain of cytokine receptors regulates intrathymic T cell development at multiple stages.

Signaling through the common gamma chain (gamma c), a subunit of the receptors for IL-2, -4, -7, -9, and -15, is critical for lymphocyte development, with the IL-7/IL-7R representing one important interaction. To investigate the stages of intrathymic T cell development that are dependent on gamma c and to determine whether gamma c controls T cell development solely as a component of the IL-7R, intrathymic T cell development was compared in IL-7R alpha-deficient mice and anti-gamma c-treated chimeric mice reconstituted with bone marrow and purified pro-T cells. In the presence of anti-gamma c, each of four phenotypically distinguishable stages of CD4- CD8- thymocytes failed to reconstitute T cell development, suggesting that each of these subsets of pro-T cells required gamma c for their differentiation and/or growth. Reconstitution of anti-gamma c-treated chimeric mice with bone marrow from IL-7R alpha-deficient mice indicated that IL-7R only partially contributed to intrathymic T cell development. Furthermore, when compared with IL-7R-deficient mice, anti-gamma c chimeric and gamma c-deficient mice exhibited a distinct phenotypic pattern of pro-T cell development. Collectively, these results indicate that several gamma c-sharing cytokines may contribute to T cell development in the thymus and suggest that one of these cytokines may be novel.

Animals↗

PubMed1997

Rotavirus RNA polymerase requires the core shell protein to synthesize the double-stranded RNA genome.

Rotavirus cores contain the double-stranded RNA (dsRNA) genome, RNA polymerase VP1, and guanylyltransferase VP3 and are enclosed within a lattice formed by the RNA-binding protein VP2. Analysis of baculovirus-expressed core-like particles (CLPs) has shown that VP1 and VP2 assemble into the simplest core-like structures with replicase activity and that VP1, but not VP3, is essential for replicase activity. To further define the role of VP1 and VP2 in the synthesis of dsRNA from viral mRNA, recombinant baculoviruses containing gene 1 (rBVg1) and gene 2 (rBVg2) of SA11 rotavirus were generated and used to express recombinant VP1 (rVP1) and rVP2, respectively. After purification, the proteins were assayed individually and together for the ability to catalyze the synthesis of dsRNA in a cell-free replication system. The results showed that dsRNA was synthesized only in assays containing rVP1 and rVP2, thus establishing that both proteins are essential for replicase activity. Even in assays containing a primer-linked mRNA template, neither rVP1 nor rVP2 alone directed RNA synthesis. Characterization of the cis-acting replication signals in mRNA recognized by the replicase of rVP1 and rVP2 showed that they were the same as those recognized by the replicase of virion-derived cores, thus excluding a role for VP3 in recognition of the mRNA template by the replicase. Analysis of RNA-protein interactions indicated that the mRNA template binds strongly to VP2 in replicase assays but that the majority of the dsRNA product neither is packaged nor stably associates with VP2. The results of replicase assays performed with mutant VP2 containing a deletion in its RNA-binding domain suggests that the essential role for VP2 in replication is linked to the protein's ability to bind the mRNA template for minus-strand synthesis.

Animals↗

PubMed1996

Interleukin-7 receptor alpha is essential for the development of gamma delta + T cells, but not natural killer cells.

Mice that lack a functional gamma c subunit of the receptors for interleukin (IL)-2, IL-4, IL-7, IL-9, and IL-15 display profound defects in lymphoid development. The IL-7/IL-7R system represents a critical interaction for conventional T and B cell development. In this report, the role of IL-7R alpha in the development of lymphoid lineages other than conventional T and B cells was examined. We demonstrate that gamma delta + T cells were absent in IL-7R alpha-deficient mice, whereas the development and function of natural killer cells were normal. Thus, IL-7R alpha function is required for the development of gamma delta + T cells but not natural killer cells.

Animals↗

PubMed1995

The IL-2 receptor gamma c chain does not function as a subunit shared by the IL-4 and IL-13 receptors. Implication for the structure of the IL-4 receptor.

The IL-2 receptor (IL-2R) gamma c subunit is also a component of the receptors for IL-4, IL-7, IL-9, and IL-15. The IL-4R and IL-13R appear to share a common subunit, and gamma c was proposed to be this shared subunit. In this study, we have assessed the relative contribution of gamma c to the mouse IL-4R and IL-13R. The MC/9 mast cell line constitutively expresses gamma c and proliferates to IL-4 and IL-13, but only the response to IL-4 was blocked by anti-gamma c mAbs. After transfection of the IL-4- and IL-13-responsive gamma c-negative B9 plasmacytoma with full length (m gamma) or cytoplasmic-tailless gamma c cDNA (m gamma t), only the proliferative response to IL-4 was affected by the surface expression of these gamma c molecules. The inability of m gamma or m gamma t expression to affect IL-13-induced proliferation by B9 indicates that gamma c does not obviously contribute to the IL-13R and does not function as the shared subunit of the IL-4R and IL-13R. This study suggests that there are two distinct IL-4R, one of which is independent of gamma c.

Animals↗

PubMed1995

Blockade of T- and B-lymphocyte development by antibody to the gamma c subunit of the receptors for interleukins 2, 4, and 7.

Cytokines are important regulators of hematopoesis. Mutations in gamma c, which is a subunit shared by the receptors for interleukin (IL) 2, IL-4, and IL-7, have been causally associated with human X chromosome-linked severe combined immunodeficiency disease. This finding indicates a mandatory role for cytokine receptor signaling at one or more stages of lymphocyte development. To evaluate the cellular level at which gamma c is critical for lymphopoiesis, the effect of monoclonal antibodies to gamma c on the capacity of syngeneic bone marrow cells to reconstitute the hematopoietic compartment of lethally irradiated recipient mice was examined. We show that monoclonal antibody to gamma c blocked lymphocyte development at or before the appearance of pro-B cells and prior to or at the seeding of the thymus by precursor cells while erythromyeloid cell development was normal. These results suggest that one level of lymphocyte development that requires gamma c is a point in hematopoietic cell differentiation near the divergence of lymphopoiesis and erythromyelopoesis.

Animals↗

PubMed1995

Expression and function of the gamma c subunit of the IL-2, IL-4, and IL-7 receptors. Distinct interaction of gamma c in the IL-4 receptor.

IL-2R, IL-4R, and IL-7R share a common subunit referred to as gamma c and the IL-13R has been proposed to contain gamma c as a subunit. In this report we have used two novel mAbs (3E12 and 4G3) to distinct epitopes of mouse gamma c to determine its lymphoid cell distribution and to examine whether gamma c uses similar epitopes to interact with different cytokines and cytokine receptors. FACS analysis revealed that gamma c is expressed in most lymphocytes, myeloid cells, embryonic thymocytes, and lymphoid cell lines. Results from radiolabeled ligand binding studies, biochemical analysis of ligand-receptor cross-linked complexes, and cytokine bioassays indicate that the epitope defined by mAb 4G3 closely defines the IL-7 binding region of gamma c and overlaps the IL-2 binding region of gamma c. These studies also indicate that gamma c interacts with IL-4 in the context of the IL-4R in a manner that is distinct from its role in the IL-2R and IL-7R and suggest that the 3E12 epitope defines a region of gamma c that intimately interacts with the IL-4R. The B9 plasmacytoma, which proliferates in response to IL-4 and IL-13, was shown to not express gamma c. Thus, at least in some circumstances, gamma c is dispensable for signaling via the IL-4R and is not a required subunit of the IL-13R.

Animals↗

PubMed1995

Detection of replicative form of HCV RNA in peripheral blood leukocytes and its clinical significance.

Nested RT-PCR, done by using degenerated primer pair, was used to detect hepatitis C virus RNA (HCV RNA) in serum, plasma, liver and peripheral blood mononuclear cells (PBMC) of 30 patients with acute and chronic posttransfusion hepatitis C and 7 asymptomatic anti-HCV positive subjects. The results showed that the percentages of both the plus and minus strands of HCV RNA in PBMC of the patients with chronic hepatitis C was significantly higher than that with acute hepatitis C and asymptomatic anti-HCV positive subjects (P < 0.05-0.001). In 17 patients who were subjected to biopsy, the positive rate of the both strands of HCV RNA in PBMC of the patients with AH was lower than that of CAH (P < 0.05). In serum and plasma of all 37 cases, the minus strand of HCV RNA was not detected. Both plus and minus strands in liver of one patient with AH were positive, but the minus strand in PBMC negative. In 6 patients with CAH whose both strands in liver were positive, both strands in PBMC in 5 patients were also found. The present data confirmed that PBMC of the patients with hepatitis C were infected by HCV and the longer the infection time, the bigger the possibility of PBMC infection by HCV. The patients with active liver disease (CAH) had higher positive rate of minus strands of HCV RNA in PBMC. The results suggested that HCV may not only infect PBMC but also replicate in PBMC, and that the occurrence of minus strand of HCV RNA is associated with activity of liver disease.

Adult↗

PubMed1995

Biochemical identity and characterization of the mouse interleukin-2 receptor beta and gamma c subunits.

Although the mouse IL-2 receptor (IL-2R) beta and gamma c subunits have been identified by molecular cloning, the biochemical identity of these subunits has not yet been established. In the present study, the mouse IL-2R was biochemically characterized from cell lines expressing normal and aberrant IL-2R. Using novel monoclonal antibodies specific for the beta or gamma c subunits, we established that the M(r) of the beta chain is 90,000-100,000 and that of the gamma c subunit is 75,000-80,000. Analysis of transfected EL4 cells that expressed alpha, gamma c, and truncated beta subunits or mutant EL4 cells, which selectively lacked cell surface gamma c, revealed that no other material migrated to a position on SDS-PAGE characteristic of IL-2/IL-2R beta and IL-2/IL-2R gamma c cross-linked complexes, respectively. Thus, the beta and gamma c subunits appear to be the sole IL-2R constituents of these IL-2 cross-linked complexes. The IL-2/IL-2R gamma c, but not the IL-2/IL-2R beta, complex exhibited enhanced mobility after SDS-polyacrylamide gel electrophoresis under nonreducing conditions, suggesting a more compact structure for gamma c as a result of intrachain disulfide bonds. The primary posttranslational modification of the mouse beta and gamma c subunits is N-linked glycosylation. These biochemical studies reconcile past uncertainties concerning the subunit composition of the mouse IL-2R and are consistent with a model of the IL-2R containing only three subunits.

Amidohydrolases↗

PubMed1994

A research on DLA-DRB1 genotyping by PCR-RFLP. I. To select a appropriate oligonucleotide primer pair.

In order to study the DLA (Dog Leucocyte Antigen) class II region we utilized the polymerase chain reaction based restriction fragment length polymorphism (PCR-RFLP) method, which has been reported previously as an efficient and simple technique for accurate definition of the HLA class II alleles. To search for a appropriate primer pair a series of amplifications with 4 different primer pairs DLA-DR-SP/Stop, DLA-DR-SP/P3, HLA-DRB-GH46/50 and HLA-DRB-AMP-A/B were provided. Only one satisfactory amplification was obtained with the primer pair HLA-DRB-AMP-A/B. The analogous sequences of the primer pair are found in the sequence of HLA-DRB-cDNA. The amplification region of the primer pair includes also the three hypervariable regions (HVR) in the sequence of DLA-DRB cDNA. Southern blot hybridization analysis confirmed the specificity of the primer pair HLA-DRB-AMP-A/B. The results of Hae III and Hinfl digestion show high polymorphism in DLA-D region and allele specific polymorphic patterns. Therefore, it is suggested that the primer pair HLA-DRB-AMP-A/B is at present the only available and usefull primer pair in PCR-RFLP study of DLA-DRB1 gene.

Alleles↗

PubMed1994

Researches on DLA-DRB1 genotyping by PCR-RFLP. II. A study of serology and cellularly defined DLA haplotypes and their segregation.

The polymerase chain reaction based restriction fragment length polymorphism (PCR-RFLP) method was used to study DLA class II gene in dogs. Genomic DNA from 11 DLA homozygous reference dogs representing 8 different haplotypes and 2 families with a total of 16 animals were amplified by the oligonucleotide primer pair (HLA-DRB-AMP-A/B) cross-hybridizing HLA-DRB specific and fit for the amplification of DLA-DRB1 gene. The corresponding amplified DNA products were 235 base pairs. Amplified DNA was digested by 32 different restriction endonucleases, which could recognize allelic variations within DLA-DRB. After digesting only with Hae III, Hha I, Hinf I, Rsa I and Sau96 I high polymorphism was revealed respectively and 9 distinct RFLP pattern were shown, which could be correlate to the DLA haplotypes studied. The 8 cellular established DLA-D specificities present in the reference panel were defined unequivocally by PCR-RFLP and correlated with DLA-Dw5 and Dw6 two subtypes. The segregation pattern of four different DLA-DRB types could be demonstrated in two families. Based on these data we conclude that PCR-RFLP typing utilizing the above mentioned primer pair and endonucleases is a valuable tool to define DLA class II types in the dog.

Alleles↗