Biomedical subjects

Zhe-Xiong Lian

Publications and source records attributed to Zhe-Xiong Lian.

At least 19 recordsLinked to original sources

PubMed2006

IL-2 receptor alpha deficiency and features of primary biliary cirrhosis.

Congenital immune deficiency states have often been valuable experimental models of nature that have significantly enhanced our understanding of the immune response. The relationship between CD4+, CD25+ and Treg cells in the induction of autoimmunity has attracted significant attention. We report herein a male child of consanguineous parents who developed at six months recurrent infections, and at age 5 years, liver dysfunction with serological expression of primary biliary cirrhosis (PBC), an autoimmune liver disease that usually affects middle-aged women. Histologically, there was intense mononuclear cell lymphoid infiltration of the intrahepatic portal tracts, CD3+CD4+T cell lymphopenia in blood and serum antibody to PDC-E2. Peripheral blood lymphocytes were completely deficient of the alpha subunit of the IL-2 receptor (IL-2Ralpha, CD 25), a marker for regulatory T cells (Tregs). Allogenic stem cell transplantation led to full recovery. This case illustrates the role of deficiency of CD4+CD25+ Treg cells in causing autoimmunity, and speaks to the potential use of allogenic stem cell transplantation for immunoreconstitution in adult PBC.

Autoimmunity↗

PubMed2006

Anti-mitochondrial antibodies and primary biliary cirrhosis in TGF-beta receptor II dominant-negative mice.

Primary biliary cirrhosis (PBC) is an autoimmune disease of the liver, characterized by lymphocytic infiltrates in portal tracts, selective destruction of biliary epithelial cells, and anti-mitochondrial Abs (AMAs). The elucidation of early events in the induction of tissue inflammation and autoimmunity in PBC has been hampered by the cryptic onset of the disease, the practical limitations in accessing the target tissue, and the lack of a suitable animal model. We demonstrate in this study that a mouse transgenic for directed expression of a dominant-negative form of TGF-beta receptor type II (dnTGFbetaRII), under the direction of the CD4 promoter, mimics several key phenotypic features of human PBC, including spontaneous production of AMAs directed to the same mitochondrial autoantigens, namely PDC-E2, BCOADC-E2, and OGDC-E2. The murine AMAs also inhibit PDC-E2 activity. Moreover, there is lymphocytic liver infiltration with periportal inflammation analogous to the histological profile in human PBC. Additionally, the serum cytokine profile of affected mice mimics data in human PBC. The concomitant presence of these immunopathological features in the transgenic mice suggests that the TGF-betaRII pathway is implicated in the pathogenesis of PBC. Finally, these data point away from initiation of autoimmunity by mechanisms such as molecular mimicry and more toward activation of an intrinsically self-reactive T cell repertoire in which necessary regulatory T cell influences are lacking.

Animals↗

PubMed2006

Increased killing activity and decreased cytokine production in NK cells in patients with primary biliary cirrhosis.

Although the pathogenesis of primary biliary cirrhosis (PBC) remains enigmatic, the immune system plays a key role in the initiation and subsequent development of pathology. Previous studies have indicated a critical role of the innate immune system. Importantly, natural killer (NK) cells are abundant in liver where they serve as sentinels of the immune system. In addition, NK cells have significant biologic activity based on their production of immunoregulatory cytokines. To address this issue, we have investigated several qualitative and quantitative activities of NK cells in patients with PBC as well as normal and liver diseased controls. We report herein a marked increase in the frequency and absolute number of blood and liver NK cells in PBC patients. Moreover, the cytotoxic activity and perforin expression by isolated NK cells were significantly increased in PBC patients associated with increased levels of plasma IL-8 and the expression of CD128a (IL-8 receptor) on NK cells. In contrast, the levels of IFN-gamma, IL-6 and IL-8 synthesized by NK cells were significantly decreased in PBC patients as compared to controls. In conclusion, data from this study provide compelling evidence supporting a biologic role of NK cells in the immunopathogenesis of PBC.

Adult↗

PubMed2006

B cells and autoimmune liver diseases.

Autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) are the three major autoimmune diseases affecting the liver. They are all characterized by the presence of a variety of autoantibodies, some of which are found in all three diseases, whereas others are restricted to one or two of them or are even specific for the particular disease. In this review we will first provide details of the serological features of these three autoimmune diseases that target the liver. In addition, we will highlight the possible pathogenic roles of autoreactive B cells, focusing on their immunological functions as autoantibody producing cells and as antigen-presenting cells for T cell priming. As well, we will describe the contribution of toll-like receptor (TLR) signaling to the activation of autoimmune B cells and the putative role of defects in regulatory T cell function in the development of autoimmune liver diseases.

Animals↗

PubMed2006

Liver-targeted and peripheral blood alterations of regulatory T cells in primary biliary cirrhosis.

CD4+CD25high regulatory T cells (Tregs) play a critical role in self-tolerance, as seen in murine autoimmunity. Studies on Tregs in human autoimmunity have focused primarily on peripheral blood samples. A study targeting diseased tissue should identify direct relationships between Tregs and autoimmunity. Peripheral blood samples were collected from 91 patients with primary biliary cirrhosis (PBC), 28 immediate relatives, and 41 healthy controls, and Treg frequencies were determined as a percentage of CD4+CD25high T cells in CD4+TCR-alphabeta+ T cells. A tissue-targeted determination of frequency and distribution of FoxP3+ Tregs was also performed on 90 different liver tissue specimens exhibiting PBC (n = 52), chronic hepatitis C (CHC) (n = 30), and autoimmune hepatitis (AIH) (n = 8). Treg suppression studies were performed on 50 PBC patients and 27 controls. Patients with PBC demonstrated a relative reduction of Tregs compared with controls (P < .0002). Interestingly, a deficiency in CD4+CD25+ Tregs was also found in the daughters and sisters of PBC patients compared with controls (P < .0007). However, functional studies did not reveal a global PBC Treg defect. The level of FoxP3-expressing Tregs was markedly lower in affected PBC portal tracts compared with CHC and AIH (P < .001). In addition, the CD8+T cell/FoxP3+ Treg ratio was significantly higher in livers of late-stage PBC compared with those of CHC (P < .001) and early-stage AIH (P < .001). In conclusion, these data provide support for a genetic modulation of Treg frequency and illustrate the role Tregs play in the loss of tolerance in PBC.

Autoimmunity↗

PubMed2006

IL-2 receptor alpha(-/-) mice and the development of primary biliary cirrhosis.

Recently, we identified a child born with a genetic deficiency of IL-2 receptor alpha (IL-2Ralpha, CD25) expression who had several clinical manifestations of primary biliary cirrhosis (PBC). In addition, there has been suggestive evidence in both patients with PBC and their first-degree relatives that a deficiency of regulatory T cells (Tregs) is an integral component for susceptibility to PBC. Based on these observations, we generated IL-2Ralpha/CD25 deficient (IL-2Ralpha(-/-)) mice and wild-type littermate controls and followed them longitudinally for the natural history of liver immunopathology and appearance of antimitochondrial antibodies (AMAs). The analyses included immunohistochemical staining of liver and portal tract infiltrates as well as FACS profiles of lymphoid subpopulations in liver and spleen. In addition, serum cytokine profiles were quantitated. Importantly, IL-2Ralpha(-/-), but not littermate controls, develop portal inflammation and biliary ductular damage similar to human patients with PBC. CD4(+) and CD8(+) T cells predominate among portal cell infiltrates and sera reflect a Th1 cytokine bias with increased levels of IFN-gamma, TNF-alpha, IL-2 and IL-12p40. Of importance is the finding that the IL-2Ralpha(-/-) mice not only develop significantly increased serum levels of IgG and IgA, but they also develop AMAs with specificity for PDC-E2, which maps to the inner lipoyl domain of the autoantigen, all characteristics which are hallmarks of human PBC. In conclusion, the IL-2Ralpha(-/-) mice should facilitate studies of the early events in PBC and especially the tantalizing connection between Treg deficiency and autoimmunity specifically directed to mitochondrially located PDC-E2 and subsequent biliary ductular cell damage.

Animals↗

PubMed2005

Plasmacytoid dendritic cells of different origins have distinct characteristics and function: studies of lymphoid progenitors versus myeloid progenitors.

Plasmacytoid dendritic cells (pDCs) play a central role in host innate and adaptive immunity and are thought to be of lymphoid origin. However, in IL-7Ralpha-/- mice, which are deficient in T and B lymphocytes, pDCs are still found in lymphoid organs, which suggests that there is a lymphoid-independent pathway for the development of pDCs. Previous work has demonstrated that pDCs originate from both lymphoid and myeloid progenitors (MPs). However, it is not clear whether the function of pDCs is different relative to their origin. In an effort to compare the characteristics and functions between pDCs generated from different progenitors, we performed adoptive transfer studies using highly enriched populations of common lymphoid progenitors (CLPs) and MPs from the bone marrow of control mice and examined their potential and developmental kinetics for the generation of pDCs. Interestingly, although CLPs were polarized to generate pDCs, MPs were polarized to generate conventional dendritic cells and the kinetics of pDC generation from MPs was reached earlier than from CLPs. Furthermore, CLPs have the potential to generate more pDCs on a per cell basis. Moreover, MP-derived pDCs produce relatively higher levels of IFN-alpha than CLP-derived pDCs following CpG stimulation. These data indicate that MPs are multipotential and have the capacity to develop into not only myeloid cells, but also pDCs, which have distinct characteristics and function compared to that of lymphoid origin and, therefore, imply a more important role for MP-derived pDCs in conditions where the function of lymphoid progenitors is impaired or compromised.

Adoptive Transfer↗

PubMed2005

Increased levels of chemokine receptor CXCR3 and chemokines IP-10 and MIG in patients with primary biliary cirrhosis and their first degree relatives.

Infiltrating memory T cells play an important role in the destruction of the biliary tract in primary biliary cirrhosis (PBC) and inflammatory chemokines control lymphocyte traffic through their interactions with T cell chemokine receptors. In the present study, we measured plasma levels of chemokines interferon-gamma-inducible protein-10 (IP-10) and monokine induced by gamma interferon (MIG), and also studied the expression of CXCR3 chemokine receptors in 105 subjects, including 53 patients with PBC, 26 first degree relatives and 26 healthy controls. Interestingly, plasma IP-10 and MIG levels in PBC were increased significantly compared to controls and appeared to increase with disease progression. By immunohistochemistry, IP-10 and MIG expressions were evident in the portal areas in PBC. Further, the frequency of CXCR3-expressing cells in peripheral blood was also significantly higher in PBC, and CXCR3-positive cells were also found in the portal areas of diseased livers, primarily on CD4+ cells. Finally, the daughters and sisters of PBC patients also demonstrated increased plasma levels of IP-10 and MIG, but, in contrast, displayed normal frequency of CXCR3+ expressing peripheral blood lymphocytes. Our data imply a role for specific chemokine-chemokine receptor interactions in the pathogenesis of PBC and also highlight the familial risk factor.

Adult↗

PubMed2005

CD4- plasmacytoid dendritic cells (pDCs) migrate in lymph nodes by CpG inoculation and represent a potent functional subset of pDCs.

We have recently identified two groups of plasmacytoid dendritic cells (pDCs) isolated from murine liver based on the expression of CD4 and other cell surface markers uniquely expressed by pDCs. Herein, we describe the identification of both CD4+ and CD4- pDCs that clearly exist in lymph nodes (LNs), spleen, liver, thymus, bone marrow, and lung. Normally, CD4+ pDCs are enriched in LNs. However, after in vivo systemic injection with bacterial CpG, a larger number of CD4- pDCs are recruited to the LNs and local inoculation by CpG drives CD4- pDCs migrating into local sentinel LNs, suggesting that CD4- pDCs are the main subpopulation migrating to the peripheral LNs. Furthermore, although both freshly isolated CD4+ pDCs and CD4- pDCs appear as an immature plasmacytoid cell and develop into a DC morphology following activation, the two subsets have strikingly different immune features, including differences in the production pattern of cytokines stimulated with CpG and in T cell activation.

Animals↗

PubMed2005

Regulatory T cells: development, function and role in autoimmunity.

The crucial role of regulatory cells in self-tolerance and autoimmunity has been clearly established in numerous types of regulatory cells, the majority of which are CD4(+) T cells. Much focus has been placed on thymically derived CD4(+)CD25(+) regulatory T cells, given that the depletion of this subset in murine models results in the spontaneous development of autoimmune diseases. These naturally occurring regulatory T cells are found to be functionally mature in the thymus, and exert suppression in a contact-dependent manner. Another important category of immunosuppressive cells consists of conditionally induced regulatory T cells such as Tr1, Th3, and various other CD4(+) lymphocytes. Understanding the development and regulatory functions of immunoregulatory cells may elucidate the etiology for loss of self-tolerance. This review will summarize the characteristics, developmental pathways, and functions of regulatory T cells, as well as their role in human autoimmune diseases including multiple sclerosis, rheumatoid arthritis, Myasthenia Gravis, Kawasaki disease, autoimmune polyglandular syndrome type II, type 1 diabetes, autoimmune lymphoproliferative syndrome, and systemic lupus erythematosus.

Autoimmune Diseases↗

PubMed2005

Altered monocyte responses to defined TLR ligands in patients with primary biliary cirrhosis.

The role of the adaptive immune response, with regard to the development of autoantibodies, has been extensively studied in primary biliary cirrhosis (PBC). However, the importance of innate immunity has been noted only recently. Based on the proposed role of microorganisms in the pathogenesis of the disease, we hypothesize that patients with PBC possess a hyper-responsive innate immune system to pathogen-associated stimuli that may facilitate the loss of tolerance. To address this issue, we isolated peripheral blood monocytes from 33 patients with PBC and 26 age-matched healthy controls and stimulated such cells in vitro with defined ligands for toll-like receptor (TLR) 2 (lipoteichoic acid; LTA), TLR3 (polyIC), TLR4 (lipopolysaccharide; LPS), TLR5 (flagellin), and TLR9 (CpG-B). Supernatant fluids from the cultures were analyzed for levels of 5 different pro-inflammatory cytokines, interleukin (IL)-1beta, IL-6, IL-8, IL-12p70, and TNF-alpha. After in vitro challenge with TLR ligands, PBC monocytes produced higher relative levels of pro-inflammatory cytokines, particularly IL-1beta, IL-6, IL-8, and TNF-alpha, compared with controls. In conclusion, monocytes from patients with PBC appear more sensitive to signaling via select TLRs, resulting in secretion of selective pro-inflammatory cytokines integral to the inflammatory response that may be critical in the breakdown of self-tolerance.

Adult↗

PubMed2005

Genetic polymorphisms of toll-like receptor 9 influence the immune response to CpG and contribute to hyper-IgM in primary biliary cirrhosis.

The serum hallmark of primary biliary cirrhosis (PBC) is the presence of anti-mitochondrial antibodies (AMA), found in 95% of patients. However, nearly every patient with PBC, including those who are AMA-negative, has an elevation in serum IgM. This hyper-IgM is neither representative of other Ig isoforms, nor is due to the levels of AMA. In fact, we have recently reported that the hyper-IgM is an innate immune response and can be induced with CpG-B with concurrent up-regulation of toll-like receptor 9 (TLR9). Based on these observations, we performed a two-tier study. First, we quantitated TLR9 genotypes in patients with PBC and controls and correlated these data with the B cell response to CpG-B. Second, based on these data, we performed an extensive TLR9 genotyping in a large cohort of patients and controls. We report herein that the 2848 AA TLR9 genotype is associated with enhanced gene expression and higher frequency of intracellular IgM(+) B cells following CpG stimulation. Interestingly, however, despite the functional association, there is no difference in the distribution of TLR9 genotypes between patients and controls. Our data emphasize the importance of dissecting the innate immune response in PBC.

Adult↗

PubMed2005

Bacterial CpG induces hyper-IgM production in CD27(+) memory B cells in primary biliary cirrhosis.

BACKGROUND AND AIMS: Sera from patients with primary biliary cirrhosis (PBC) are characterized by the presence of antimitochondrial antibodies and elevated levels of immunoglobulin (Ig) M. We hypothesized that the increase in serum IgM is the result of chronic B-cell activation induced via the Toll-like receptor (TLR) signaling pathway. METHODS: We analyzed peripheral blood mononuclear cells (PBMCs) from patients with PBC and controls following incubation with CpG, a natural ligand for TLR9, and determined the basal and stimulated levels of intracellular IgM, the density of TLR9, and the contribution of specific B-cell subpopulations. RESULTS: Our data demonstrate uniquely that in vitro incubation of PBMCs from PBC with CpG-B, but not CpG-A, led to a markedly high frequency of intracellular IgM-positive B cells, associated with high levels of synthesized IgM and identified to be a function of CD27(+) memory B cells. This memory B-cell subset also expressed higher densities of TLR9 as compared with naive B cells. These results were not due to increased proliferation, as defined by 5-carboxyfluoresein diacetate succinimidyl ester labeling, or an increase in the life span of B cells, as defined by Bcl-2 expression. CONCLUSIONS: These findings for the first time identify a major role for innate immune mechanisms in the induction and persistence of abnormal humoral immune responses in PBC.

Antigens, CD↗

PubMed2005

Prss16 is not required for T-cell development.

PRSS16 is a serine protease expressed exclusively in cortical thymic epithelial cells (cTEC) of the thymus, suggesting that it plays a role in the processing of peptide antigens during the positive selection of T cells. Moreover, the human PRSS16 gene is encoded in a region near the class I major histocompatibility complex (MHC) that has been linked to type 1 diabetes mellitus susceptibility. The mouse orthologue Prss16 is conserved in genetic structure, sequence, and pattern of expression. To study the role of Prss16 in thymic development, we generated a deletion mutant of Prss16 and characterized T-lymphocyte populations and MHC class II expression on cortical thymic epithelial cells. Prss16-deficient mice develop normally, are fertile, and show normal thymic morphology, cellularity, and anatomy. The total numbers and frequencies of thymocytes and splenic T-cell populations did not differ from those of wild-type controls. Surface expression of MHC class II on cTEC was also similar in homozygous mutant and wild-type animals, and invariant chain degradation was not impaired by deletion of Prss16. These findings suggest that Prss16 is not required for quantitatively normal T-cell development.

Animals↗

PubMed2004

Expansion of bone marrow IFN-alpha-producing dendritic cells in New Zealand Black (NZB) mice: high level expression of TLR9 and secretion of IFN-alpha in NZB bone marrow.

Patients with systemic lupus erythematosus have elevated IFN-alpha production. Furthermore, sera IFN-alpha levels correlate with disease activity. We have focused our attention on whether this phenotype is also seen in the New Zealand Black (NZB) mice and simultaneously addressed the underlying mechanisms. Specifically, we analyzed: 1) levels of sera IFN-alpha after type A CpG ODN 2216 injection in autoimmunity-prone NZB and control mice, and 2) levels of IFN-alpha synthesized by IFN-alpha-producing dendritic cells (IPDCs) using highly enriched populations of CD11c+B220+ IPDCs derived from NZB and control mice; IPDCs are divided into two subpopulations (CD4+CD11c+B220+ and CD4-CD11c+B220+). Our data demonstrate that NZB mice produced higher levels of sera IFN-alpha after type A CpG ODN 2216 injection when compared with control mice (p < 0.01). In addition, the cell numbers, frequency, and TLR9 mRNA levels of CD4+ and CD4- IPDC were markedly increased in the bone marrow (BM) of NZB mice. Upon in vitro stimulation with TLR9 ligand-CpG ODN 2216, higher levels of IFN-alpha were synthesized by IPDCs from the BM of NZB. The major contributor of IFN-alpha was the CD4-CD11c+B220+ IPDC subpopulation. Furthermore, NZB BM IPDCs manifest impaired expression of homing chemokine CCR7 and CD62L, and IL-12 production. These data on the functional characteristics of the IPDC lineages explain in part the mechanism of hyper-IFN-alpha production and help clarify the mechanism for the expansion of NZB BM IPDCs.

Animals↗

PubMed2003

Heterogeneity of dendritic cells in the mouse liver: identification and characterization of four distinct populations.

Liver dendritic cells (DC) are believed to play important roles in liver immunity, autoimmunity, and in the regulation of hepatic allograft acceptance. However, limited information is available on the phenotypes and functions of DC in the liver. To address this issue, we isolated DC from murine liver using procedures that do not involve collagenase, and characterized the freshly isolated DC population that had not been subjected to in vitro expansion. Thence, based on the expression of CD4, B220, and CD11b, four subsets or groups of hepatic NK1.1(-)CD11c(+) DC were identified with the following phenotypes: B220(+)CD4(+), B220(+)CD4(-), B220(-)CD11b(+), and B220(-)CD11b(-). Each subset was further characterized both phenotypically and functionally. In addition to unique phenotypic expression, each subset displayed different allostimulation capability in mixed lymphocyte reaction assays. All four groups developed DC morphology following in vitro culture with activation agents and synthesized distinct patterns of cytokines in response to different stimuli. Taken together, our results suggest that groups I and II are IFN-alpha-producing plasmacytoid DC, group III cells are myeloid-related DC, while group IV is a heterogeneous population containing both myeloid- and lymphoid-related DC. Our results demonstrate the highly heterogeneous nature of hepatic DC, which is in agreement with the unique requirements for APC in the complex liver environment.

Animals↗

PubMed2003

Murine thymic plasmacytoid dendritic cells.

We report herein heterogeneous murine thymic cell subsets expressing CD11c and B220 (CD45R). The CD11c(+)B220(+) subset expresses Ly6C(high) and MHC class II(low) in contrast with previously described thymic DC (CD11c(+)B220(-) cells). Freshly isolated thymic CD11c(+)B220(+) cells show typical plasmacytoid morphology which differentiates to mature DC, in vitro with CpG oligodeoxynucleotides (ODN) 2216; we term this subset thymic plasmacytoid DC (pDC). These thymic pDC are highly sensitive to spontaneous apoptosis in vitro and induce low T cell allo-proliferation activity. Thymic pDC express low TLR2, TLR3 and TLR4 mRNA, normally found on human immature DC, and high TLR7 and TLR9 mRNA, normally found on human pDC. Thymic pDC also produce high amounts of IFN-alpha following culture with CpG ODN 2216 (TLR9 ligands) as compared with the previously defined thymic DC lineage which expresses low TLR9 mRNA and produce high IL-12 (p40) with CpG ODN 2216. These results indicate that thymic pDC are similar to IFN-producing cells as well as human pDC. The TLR and cytokine production profiles are consistent with a nomenclature of pDC. The repertoire of this cell lineage to TLR9 ligands demonstrate that such responses are determined not only by the quantity of expression, but also cell lineage.

Animals↗

PubMed2003

Proteasome is required for class I-restricted presentation by Fcgamma receptor-mediated endocytosis in primary biliary cirrhosis.

There is a considerable database on the effector mechanisms for CD8 recognition of PDC-E2 in primary biliary cirrhosis (PBC). In particular, the specific roles of MHC class I, the mitochondrial autoepitope, and the liver-specific T cell precursor frequency, are defined for HLA-A2.1 patients. There is evidence for a role of MHC class I-mediated presentation of exogenous antigens, or cross-presentation, in the development of the antimitochondrial response and a contributory role of Fcgamma receptor-mediated uptake of autoantigen-autoantibody complexes for the induction of a PDC-E2 specific autoreactive CTL response. Based on this background, we examined potential intracellular pathways for processing the immunodominant mitochondrial autoantigen, PDC-E2, by dendritic cells (DC). In particular, we studied the effects of the proteasome inhibitor lactacystin and the endosomal acidification inhibitor bafilomycin on the induction of PDC-E2-specific CTL response in PBC. Importantly, our data indicate that pre-treatment with either lactacystin or bafilomycin inhibits the PDC-E2 immune complex-induced CTL response. The processing and presentation of PDC-E2 by CD8(+)T cells is mediated by proteasomes and facilitated by Fcgamma receptor-mediated endocytosis. This data reflects another layer of interaction between components of the immune system in the development of autoimmunity. Further characterization of autoantigen uptake and processing may lead to potential therapeutic intervention.

Acetylcysteine↗