Biomedical subjects

Lieping Chen

Publications and source records attributed to Lieping Chen.

At least 73 records · Page 4Linked to original sources

PubMed2003

Ligation of CD137 receptor prevents and reverses established anergy of CD8+ cytolytic T lymphocytes in vivo.

T-cell anergy is a tolerance mechanism defined as a hyporesponsive status of antigen-specific T cells upon prior antigen encounter and is believed to play a critical role in the evasion of tumor immunity and the amelioration of allogeneic transplant rejection. Molecular mechanisms in controlling T-cell anergy are less known. We show here that administration of an agonistic monoclonal antibody (mAb) to CD137, a member of the tumor necrosis factor receptor superfamily, prevents the induction of CD8+ cytolytic T-lymphocyte (CTL) anergy by soluble antigens. More importantly, CD137 mAb restores the functions of established anergic CTLs upon reencountering their cognate antigen. As a result, infusion of CD137 mAb inhibits progressive tumor growth that is caused by soluble tumor antigen-induced tolerance in a P815R model. CD137 mAb also restores proliferation and effector functions of anergic alloreactive 2C T cells in a bone marrow transplantation model. Our results indicate that ligation of CD137 receptor delivers a regulatory signal for T-cell anergy and implicate manipulation of the CD137 pathway as a new approach to break T-cell tolerance.

Animals↗

PubMed2003

Human muscle cells express a B7-related molecule, B7-H1, with strong negative immune regulatory potential: a novel mechanism of counterbalancing the immune attack in idiopathic inflammatory myopathies.

B7-H1 is a novel B7 family protein attributed to costimulatory and immune regulatory functions. Here we report that human myoblasts cultured from control subjects and patients with inflammatory myopathies as well as TE671 muscle rhabdomyosarcoma cells express high levels of B7-H1 after stimulation with the inflammatory cytokine IFN-gamma. Coculture experiments of MHC class I/II-positive myoblasts with CD4 and CD8 T cells in the presence of antigen demonstrated the functional consequences of muscle-related B7-H1 expression: production of inflammatory cytokines, IFN-gamma and IL-2, by CD4 as well CD8 T cells was markedly enhanced in the presence of a neutralizing anti-B7-H1 antibody. This observation was paralleled by an augmented expression of the T cell activation markers CD25, ICOS, and CD69, thus showing B7-H1-mediated inhibition of T cell activation. Further, we investigated 23 muscle biopsy specimens from patients with polymyositis (PM), inclusion body myositis (IBM), dermatomyositis (DM), and nonmyopathic controls for B7-H1 expression by immunohistochemistry: B7-H1 was expressed in PM, IBM, and DM specimens but not in noninflammatory and nonmyopathic controls. Staining was predominantly localized to areas of strong inflammation and to muscle cells as well as mononuclear cells. These data highlight the immune regulatory properties of muscle cells and suggest that B7-H1 expression represents an inhibitory mechanism induced upon inflammatory stimuli and aimed at protecting muscle fibers from immune aggression.

Antigens, CD↗

PubMed2003

Differential binding properties of B7-H1 and B7-DC to programmed death-1.

Programmed death-1 (PD-1) is a negative regulatory receptor expressed on activated T and B cells. Two ligands for PD-1, B7-H1 (PD-L1) and B7-DC (PD-L2), have been identified, but their binding properties have not been characterized yet. In this study, we generated soluble Ig fusion proteins of these molecules and examined the kinetics and relative affinities of the interactions between B7-H1 or B7-DC and PD-1 by flow cytometry and surface plasmon resonance. The interaction of B7-DC/PD-1 exhibited a 2-6-fold higher affinity and had different association/dissociation kinetics compared with the interaction of B7-H1/PD-1. Our results suggest that the differential binding properties of B7-H1 and B7-DC may be responsible for differential contributions of these two PD-1 ligands to immune responses.

Animals↗

PubMed2003

Cooperative B7-1/2 (CD80/CD86) and B7-DC costimulation of CD4+ T cells independent of the PD-1 receptor.

B7-DC is a recently discovered member of the B7 family that binds to PD-1 and is selectively expressed by dendritic cells (DCs). It has been shown to either costimulate or inhibit T cell responses. To assess the role of B7-DC in DC-T cell interactions, DCs from B7-DC knockout (KO) mice were generated and compared with DCs from wild-type (WT) and B7-1/B7-2 double KO mice. B7-1/B7-2-deficient DCs, while strongly diminished in their ability to stimulate naive CD4+ T cells, nonetheless retain partial activity. DCs from B7-DC KO mice are diminished in their ability to activate CD4+ T cells, demonstrating that DC-expressed B7-DC serves a predominantly stimulatory rather than inhibitory function in the initiation of T cell responses. B7-DC costimulates expression of CD40L with faster kinetics than B7-1 and displays potent synergy with B7-1 and B7-2 for T cell proliferation and cytokine production, indicating that these B7 family members work in concert to stimulate T cells. Finally, costimulation with B7-DC alone or in conjunction with B7-1 is PD-1 independent, indicating that B7-DC costimulates T cells via a second receptor.

Animals↗

PubMed2003

Characterization of antigen processing machinery and Survivin expression in tonsillar squamous cell carcinoma.

BACKGROUND: There is a statistically significant association between human leukocyte antigen (HLA) Class I antigen expression and improved prognosis for some patients. This association reflects the control of tumor growth by HLA Class I antigen-restricted, tumor-associated antigen-specific cytolytic T cells. However, progression of other malignant diseases is not associated with the loss of HLA expression. These observations show that the poor prognosis of a subset of tumors, despite high HLA Class I antigen expression, may reflect the development of alternative mechanisms utilized by tumor cells to escape from immune recognition and destruction. METHODS: The authors evaluated the possible correlation between the expression of the antiapoptosis gene, Survivin, HLA Class I, and progression of tonsillar squamous cell carcinomas (TSCC) lesions. Tissue microarrays were constructed from primary TSCC, metastatically involved lymph nodes, adjacent normal mucosa, and tonsillar parenchyma excised for nonmalignant conditions. RESULTS: Immunoperoxidase staining of tissue sections demonstrated that Survivin expression is significantly higher (P < 0.001) in malignant tumors than in normal tissue samples. In addition, Survivin expression is significantly higher (P = 0.05) in metastatic than in primary lesions. Survivin expression in primary lesions correlated positively with delta (P = 0.025), tapasin (P = 0.028), and HLA Class I antigen (P = 0.006) expression. The expression patterns of delta, tapasin, HLA Class I antigen, beta-2-microglobulin, and Survivin did not demonstrate any significant association with the clinical course of disease. CONCLUSIONS: For TSCC that maintain the expression of HLA Class I antigen, overexpression of Survivin may provide an alternative explanation for tumor progression.

Antigen Presentation↗

PubMed2003

A simple and rapid vortex method for preparing antigen/adjuvant emulsions for immunization.

The sustained release of antigen over a period of time is necessary to stimulate the immune system and generate a high titer of antibody. The use of adjuvants in water-in-oil emulsions has long been the favored method of prolonging the exposure time of antigens to enhance the immune response. Routine methods for preparation of this emulsion are repeated mixing of the materials in a "two-syringe" method that is labor-intensive and unreliable. The method we describe here is to use a common vortex (i.e. Vortex Genie 2, VWR) to prepare water-in-oil antigen/adjuvant emulsions. This method has been routinely used in our laboratory for many years and demonstrates its consistency with reliability for immunization of mice, hamsters, and rats and subsequently generation of hybridomas.

Adjuvants, Immunologic↗

PubMed2003

B7-H1 pathway and its role in the evasion of tumor immunity.

B7-H1 is a recently identified member of the B7 family molecules. Upon ligation to its receptors on T cells it regulates activation and differentiation of T cells. B7-H1 preferentially costimulates IL-10 production in resting T cells and further induces the apoptosis of activated T cells. PD-1 is a receptor of B7-H1 and is shown to mediate the inhibition of activated T cell response, presumably by inhibiting cell cycle progression. The expression of B7-H1 protein is limited to macrophage lineage of cells in normal tissues, although its mRNA transcription is found in a broad range of tissues. In contrast, B7-H1 is abundant in various human cancers. The tumor-associated B7-H1 increases apoptosis of antigen specific T cells, leading to growth of immunogenic tumor growth in vivo. Current data suggest that B7-H1 regulates the organ-specific tolerance in normal tissue and may contribute to immune evasion by cancers. Selective manipulation of B7-H1 pathway thus aids in the design of new regimens in the treatment of human autoimmune disease and the control of malignant cancers.

Antigens, CD↗

PubMed2003

Molecular modeling and functional mapping of B7-H1 and B7-DC uncouple costimulatory function from PD-1 interaction.

B7-H1 and B7-DC are ligands for PD-1, a receptor implicated in negative regulation of T and B cell functions. These ligands, however, also costimulate T cell responses. It remains elusive whether or not costimulation is mediated through PD-1. By comparative molecular modeling and site-directed mutagenesis, we found that nonconserved residues between these ligands on the A'GFCC'C" face mediate interaction with PD-1. This indicates significant structural heterogeneity of the interactions between PD-1 and its ligands. Importantly, ligand mutants with abolished PD-1 binding capacity could still costimulate proliferation and cytokine production of T cells from normal and PD-1-deficient mice. Our results reveal unique binding characteristics of B7-H1 and B7-DC and provide direct evidence for an independent costimulatory receptor other than PD-1.

Amino Acid Sequence↗

PubMed2003

Blockade of B7-H1 improves myeloid dendritic cell-mediated antitumor immunity.

Suppression of dendritic cell function in cancer patients is thought to contribute to the inhibition of immune responses and disease progression. Molecular mechanisms of this suppression remain elusive, however. Here, we show that a fraction of blood monocyte-derived myeloid dendritic cells (MDCs) express B7-H1, a member of the B7 family, on the cell surface. B7-H1 could be further upregulated by tumor environmental factors. Consistent with this finding, virtually all MDCs isolated from the tissues or draining lymph nodes of ovarian carcinomas express B7-H1. Blockade of B7-H1 enhanced MDC-mediated T-cell activation and was accompanied by downregulation of T-cell interleukin (IL)-10 and upregulation of IL-2 and interferon (IFN)-gamma. T cells conditioned with the B7-H1-blocked MDCs had a more potent ability to inhibit autologous human ovarian carcinoma growth in non-obese diabetic-severe combined immunodeficient (NOD-SCID) mice. Therefore, upregulation of B7-H1 on MDCs in the tumor microenvironment downregulates T-cell immunity. Blockade of B7-H1 represents one approach for cancer immunotherapy.

Animals↗

PubMed2003

Naturally occurring human IgM antibody that binds B7-DC and potentiates T cell stimulation by dendritic cells.

A human IgM Ab, serum-derived human IgM 12 (sHIgM12), is identified that binds mouse and human dendritic cells (DC), inducing dramatic immunopotentiation following treatment of the mouse DC in vitro. Competition, transfection, and knockout studies identified the ligand on mouse DC as the costimulatory molecule family member B7-DC. Potent T cell responses are stimulated by Ag-pulsed DC treated with the sHIgM12 Ab in vitro and upon adoptive transfer of Ab-treated Ag-pulsed DC into animals. The multivalent structure of pentameric IgM provides the potential for cross-linking cell surface targets, endowing the soluble Abs with biological potential not normally associated with immune function. The ability of the sHIgM12 Ab to potentiate the immune response is dependent on the multimeric structure of IgM, as bivalent monomers do not retain this property. Furthermore, pretreatment of DC with IgM monomers blocks subsequent potentiation by intact IgM pentamers, an indication that cross-linking of B7-DC on the cell surface is critical for potentiation of Ag presentation. These findings imply that, in addition to known costimulatory roles, B7-DC can function as a receptor for signals delivered by cells expressing B7-DC ligands.

Adjuvants, Immunologic↗

PubMed2003

Immunology of B7-H1 and its roles in human diseases.

B7-H1 was originally identified by homology analysis in comparison with B7-1 and B7-2, two molecules with important immunoregulatory functions. B7-H1, however, was broadly induced in the majority of peripheral tissues as well as hematopoietic cells. Upon binding to an as yet unidentified costimulatory receptor on primed T-cells, B7-H1 costimulates T-cell proliferation and preferentially induces interleukin 10 and interferon gamma. The costimulatory function of B7-H1 may be critical for enhancing maturation and differentiation of T-cells in lymphoid organs. Conversely, by binding to programmed death 1 receptors on activated T-cells and B-cells, B7-H1 may inhibit ongoing T-cell responses in peripheral tissues by inducing apoptosis and arresting cell-cycle progression. Although a positive regulatory role of B7-H1 has been demonstrated in vitro and in various animal models, a negative regulatory role of B7-H1 has also been documented in human diseases, including cancer, rheumatoid arthritis, and human immunodeficiency virus infection. Delineation of the complex interactions between B7-H1 and its receptors as well as its interplay with other ligands is critical for understanding this new immunoregulatory system. Precise manipulation of B7-H1 and its receptors may provide unique opportunities for designing new disease treatments.

Animals↗

PubMed2003

CD137 signaling interferes with activation and function of CD4+CD25+ regulatory T cells in induced tolerance to experimental autoimmune thyroiditis.

Experimental autoimmune thyroiditis (EAT), a model for Hashimoto's thyroiditis, is a T cell-mediated disease inducible with mouse thyroglobulin (mTg). Pretreatment with mTg, however, can induce CD4+ T cell-mediated tolerance to EAT. We demonstrate that CD4+CD25+ regulatory cells are critical for the tolerance induction, as in vivo depletion of CD25+ cells abrogated established tolerance, and CD4+CD25+ cells from tolerized mice suppressed mTg-responsive cells in vitro. Importantly, administration of an agonistic CD137 monoclonal antibody (mAb) inhibited tolerance development, and the mediation of established tolerance. CD137 mAb also inhibited the suppression of mTg-responsive cells by CD4+CD25+ cells in vitro. Signaling through CD137 likely resulted in enhancement of the responding inflammatory T cells, as anti-CD137 did not enable CD4+CD25+ T cells to proliferate in response to mTg in vitro.

Animals↗

PubMed2003

B7-H4, a molecule of the B7 family, negatively regulates T cell immunity.

We identify a B7 family molecule, B7-H4, by protein sequence analysis and comparative molecular modeling. While B7-H4 mRNA is widely distributed in mouse and human peripheral tissues, cell surface expression of B7-H4 protein is limited and shows an inducible pattern on hematopoietic cells. Putative receptor of B7-H4 can be upregulated on activated T cells. By arresting cell cycle, B7-H4 ligation of T cells has a profound inhibitory effect on the growth, cytokine secretion, and development of cytotoxicity. Administration of B7-H4Ig into mice impairs antigen-specific T cell responses whereas blockade of endogenous B7-H4 by specific monoclonal antibody promotes T cell responses. B7-H4 thus may participate in negative regulation of cell-mediated immunity in peripheral tissues.

Amino Acid Sequence↗

PubMed2003

Autoimmune diabetes in HLA-DR3/DQ8 transgenic mice expressing the co-stimulatory molecule B7-1 in the beta cells of islets of Langerhans.

The major predisposing genetic component in type 1 diabetes (T1D) maps to the MHC locus in both mice and humans. To better understand the HLA class II association with disease pathogenesis, we bred mice expressing HLA-DQ8 and -DR3, either alone or in combination, to transgenic mice expressing the co-stimulatory molecule B7-1 in the beta cells of islets of Langerhans. Spontaneous diabetes occurred only in RIP-B7-1 transgenic mice expressing transgenic HLA-DR3 or -DQ8 molecules and the incidence of diabetes was comparable between the two (approximately 30% in either sex up to 50 weeks of age). Presence of DR3 and DQ8 together only marginally elevated the overall incidence of spontaneous disease (38%). Non-specific activation of T cells by superantigen and provision of concomitant co-stimulation through 4-1BB (CD137) by an agonistic antibody did not accelerate the incidence of diabetes over a short period of time. Neither the antibody-mediated depletion of CD25+ T cells nor sublethal, whole-body irradiation of young, naive HLA transgenic mice expressing RIP-B7-1 resulted in diabetes. However, administration of only two doses of the beta cell toxin streptozotocin (STZ; 40 mg/kg) induced autoimmune diabetes in 85% of mice within 7 weeks after STZ treatment only when B7-1 was expressed on the pancreatic beta cells. This effect was HLA dependent as none of the STZ-treated RIP-B7-1 transgenic mice lacking HLA class II developed diabetes. In conclusion, this study confirmed the diabetogenic potential of HLA-DQ8 and established the role of HLA-DR3 in the pathogenesis of T1D.

Animals↗

PubMed2003

Expression of the costimulatory molecule B7-H2 (inducible costimulator ligand) by human airway epithelial cells.

Tissue structural cells are known in some situations to play a role in the presentation of antigen and in immunoregulation. We assessed the expression of B7 homologs, known to be involved in antigen presentation and lymphocyte costimulation, in human airway epithelial cells. Flow cytometry performed on the airway epithelial cell line BEAS-2B, as well as primary bronchial epithelial cells (PBEC), showed that B7-H2 was constitutively expressed on both BEAS-2B and PBEC, whereas B7-1 and B7-2 were undetectable on either epithelial cell type. B7-H2 expression was confirmed by Western blot using a specific antibody. Stimulation with various cytokines, including tumor necrosis factor-alpha, interferon-gamma, and interleukin-4, slightly downregulated B7-H2 expression detected by flow cytometry, but did not significantly alter the apparent level of protein as assessed by Western blotting. Northern blotting detected mRNA for B7-H2 and B7-1, but not B7-2. B7-H2 was cloned from BEAS-2B cells and the sequence verified. Expression of B7-H2 mRNA was detected by real-time reverse transcriptase-polymerase chain reaction in PBEC from three independent donors. Immunohistochemical analysis of airway derived from autopsies revealed expression of B7-H2 in human airway epithelial cells. These results demonstrate that airway epithelial cells express the costimulatory molecule B7-H2, and suggest the possibility that B7-H2 may participate in antigen presentation by epithelial cells.

Antigens, CD↗

PubMed2003

Costimulating aberrant T cell responses by B7-H1 autoantibodies in rheumatoid arthritis.

A pathogenic hallmark of rheumatoid arthritis (RA) is persistent activation of self-reactive CD4(+) T cells. The cause of this aberrant activity remains elusive. We report here detection of autoantibodies against B7-H1, a recently described member of the B7 family, in 29% of patients with RA versus 4% of healthy donors. High-level expression of cell surface B7-H1 are found on activated human CD4(+), CD8(+), and CD45RO(+) T cells. Immobilized autoantibodies to B7-H1 are capable of costimulating the proliferation of CD4(+) T cells in vitro, and the presence of these autoantibodies correlates with active disease status. Using immobilized B7-H1 mAb's and programmed death 1Ig, we demonstrate that engagement of B7-H1 on CD4(+) T cells costimulates proliferation and secretion of IL-10, and subsequently leads to programmed cell death, accompanied with upregulated expression of TNF-related apoptosis-inducing ligand and activation of caspase-3. Taken together with our previous findings, these data indicate a bidirectional signaling role of B7-H1 in T cell costimulation and apoptosis and implicate B7-H1 autoantibodies as contributing to the progression of RA by inducing aberrant T cell responses.

Adolescent↗

PubMed2003

Cancer therapeutic monoclonal antibodies targeting lymphocyte co-stimulatory pathways.

Monoclonal antibody (mAb) targeting to tumor antigen is an important therapeutic approach for the treatment of a variety of cancers. Both positive and negative co-stimulatory pathways are critical components for the control and fine-tuning fo immune responses and recently mAb targeting of lymphocyte co-stimulatory pathways has been investigated. With the development of agonistic and antagonistic mAbs, both positive and negative pathways can be regulated and the potent therapeutic efficacy of this method has been demonstrated in experimental models. With high affinity and selectivity, as well as humanization technology for mAbs, there is little doubt that this new approach alone, or in combination with other therapeutic modalities, will play an important role in immunotherapy for cancers in the near future.

Animals↗

PubMed2002

B7-H1 is up-regulated in HIV infection and is a novel surrogate marker of disease progression.

The ligation of programmed death-ligand 1 (B7-H1) to T cells results in the preferential production of interleukin 10 (IL-10). We investigated if B7-H1 would be up-regulated in HIV infection, a disease characterized by increased IL-10 production, by measuring B7-H1, B7-1 (CD80), and B7-2 (CD86) expression and mRNA in 36 HIV-infected patients and in 22 healthy controls (HCs). Results showed that (1) B7-H1 expression and mRNA are augmented in cells of HIV patients; (2) increased IL-10 production in these patients is largely induced by B7-H1-expressing CD14(+) cells; (3) an inverse correlation is detected between B7-H1 expression and CD4 counts, whereas the up-regulation of B7-H1 is directly associated with HIV plasma viremia; (4) antiviral therapy results in the parallel down modulation of IL-10 production and B7-H1 expression/synthesis; and (5) B7-H1/CD80 and B7-H1/CD86 mRNA ratios are increased in peripheral blood mononuclear cells (PBMCs) of HIV patients compared with HCs. B7-H1 synthesis and expression are up-regulated in HIV infection, and the degree of dysregulation correlates with the severity of disease. Aberrant antigen presentation by antigen-presenting cells (APCs) that exhibit increased B7-H1 expression and IL-10 production in HIV infection could be responsible for T-lymphocyte unresponsiveness and loss of protective immunity. B7-H1 is a surrogate marker potentially involved in AIDS disease progression.

Antigens, CD↗