Biomedical subjects

Takashi Kamihira

Publications and source records attributed to Takashi Kamihira.

9 recordsLinked to original sources

PubMed2006

Autoreactive T-cell responses in primary biliary cirrhosis are proinflammatory whereas those of controls are regulatory.

BACKGROUND & AIMS: Autoreactive T cells that proliferate in response to autoantigens are found in both autoimmune disease and controls but have important qualitative differences in relative activation states, costimulation signal requirements, and pathogenetic significance. Understanding the mechanism for activation of autoreactive T cells will be critical in the treatment of autoimmune diseases. METHODS: To understand the differences between autoreactive T cells in primary biliary cirrhosis (PBC) versus controls, we have developed autoreactive T-cell clones (TCCs) from patients with PBC and healthy controls and have used a peptide corresponding to the CD4 major autoepitope to define the relative proliferative and cytokine response. RESULTS: Using an enzyme-linked immunosorbent spot assay, peripheral blood mononuclear cells (PBMCs) from PBC, but not from controls, produce interferon (IFN)-gamma regardless of whether costimulation-competent or -incompetent antigen-presenting cells (APC) were used. In contrast, a significant number of IFN-gamma-producing cells were found in PBMCs from controls but only if costimulation-competent PBMCs presented an autoantigenic peptide. In addition, costimulation-dependent autoreactive TCCs became anergic after a single round of stimulation in the presence of APC that did not provide a costimulatory signal, whereas some costimulation-independent autoreactive TCCs required repeated stimulation to become anergic and the others did not become anergic. Finally, anergic TCCs produced interleukin-10, but no IFN-gamma, and exhibited regulatory functions in an antigen-dependent, cell contact-independent, and partially interleukin-10-mediated manner. CONCLUSIONS: These data relate specifically to the functional characteristics of autoreactive T cells in PBC but are also generically important for understanding the mechanisms for generating pathogenetic autoreactive T cells.

Autoantigens↗

PubMed2006

Human intrahepatic biliary epithelial cells function in innate immunity by producing IL-6 and IL-8 via the TLR4-NF-kappaB and -MAPK signaling pathways.

BACKGROUND: Human intrahepatic biliary epithelial cells (HIBECs) may play active roles in both the innate and adaptive immune responses. Little is known, however, about the role of toll-like receptors (TLRs) on HIBECs in inflammatory cholangiopathies. METHODS: The expression of TLR1-9 and the biological responses to their ligands, lipopolysaccharide (LPS) or lipoteichoic acid (LTA), were studied in cultured HIBECs by reverse transcription-polymerase chain reaction, immunoblotting, and enzyme-linked immunosorbent assay. RESULTS: HIBECs constitutively expressed transcripts encoding TLR1-6 and 9, as well as myeloid differentiation factor 88 (MyD88), MD2, and CD14. Stimulation of HIBECs with LPS resulted in translocation of NF-kappaB subunits from the cytoplasmic to the nuclear fraction, followed by increased secretion of a variety of chemokines/cytokines, including interleukin-8 (IL-8), monocyte chemotactic protein-1 (MCP-1), and IL-6. Treatment with BAY11-7082 efficiently inhibited the LPS-induced transcription and secretion of these chemokines/cytokines. In HIBECs, the mitogen-activated protein kinases (MAPKs) were also activated by LPS stimulation. These results indicated that LPS activates HIBECs via a TLR4-MyD88-dependent pathway. Stimulation of HIBECs with LTA induced the secretion of a similar profile of cytokines/chemokines via a TLR2-MyD88-dependent pathway. CONCLUSIONS: In HIBECs, at least TLR2 and 4 are capable of mediating innate immune system function in vitro. This result, in conjunction with our recent finding that TLR4 expression is increased in biliary epithelial cells in primary biliary cirrhosis, suggests the involvement of TLRs in the development of chronic inflammatory cholangiopathies.

Bile Duct Diseases↗

PubMed2005

Increased expression of nuclear envelope gp210 antigen in small bile ducts in primary biliary cirrhosis.

The sustained antibody response to nuclear envelope gp210 antigen indicates a group of primary biliary cirrhosis (PBC) patients at high risk for the progression to end-stage hepatic failure. To address this issue, we immunohistochemically studied the expression of gp210 antigen in needle liver biopsy specimens from PBC patients using a monoclonal antibody specific for gp210 antigen. The specimens from autoimmune hepatitis (AIH), chronic viral hepatitis B (CHB) and C (CHC) patients served as disease controls. The expression of gp210 antigen was apparently increased on the nuclear envelope of biliary epithelial cells (BECs) of small bile ducts in almost all specimens from PBC. In contrast, the expression of gp210 antigen was negative in BECs of small bile ducts in normal liver, while relatively weak anti-gp210 immunostaining was observed in AIH, CHC and CHB. In addition, the degree of gp210 expression in BECs of small bile ducts was positively correlated to that of portal inflammation, interface hepatitis and lobular inflammation in PBC. These results indicate that the increased expression of gp210 in small bile ducts, which is probably associated with damage to BECs by inflammation, is possibly involved in autoimmune response to gp210 leading to the progression to end-stage hepatic failure in PBC.

Adult↗

PubMed2005

Biliary epithelial cells regulate autoreactive T cells: implications for biliary-specific diseases.

The biliary epithelial cell (BEC) is the target for several human immune mediated liver diseases, including primary biliary cirrhosis, but it is not always clear whether the BEC functions as an accessory cell or an antigen presenting cell, although it is well documented that BECs express high levels of human leukocyte antigen Class II, intercellular adhesion molecule-1, and lymphocyte function-associated antigen-3. To examine this issue, we established autoreactive T-cell clones from human leukocyte antigen-DR53 patients with primary biliary cirrhosis and characterized BEC function as a function of the ability of BECs to regulate T-cell activation. We report herein that BEC-mediated T-cell activation occurs partially via programmed death 1 ligands in a cell-contact-dependent manner. Further, such activation occurs via prostaglandin E2 production in a cell-contact-independent fashion. Moreover, the production of prostaglandin E2 was partially controlled by interleukin-1beta and tumor necrosis factor alpha. In conclusion, the regulatory activities of BECs are important for the maintenance of peripheral immune tolerance. Further, modulation of BEC function may be used for therapeutic modulation.

Antigen-Presenting Cells↗

PubMed2005

Fractalkine and CX3CR1 are involved in the recruitment of intraepithelial lymphocytes of intrahepatic bile ducts.

Fractalkine is a chemokine with both chemoattractant and cell-adhesive functions, and in the intestine it is involved with its receptor CX3CR1 in the chemoattraction and recruitment of intraepithelial lymphocytes. We examined the pathophysiological roles of fractalkine and CX3CR1 in normal and diseased bile ducts. Expression of fractalkine and CX3CR1 were examined in liver tissues from patients with primary biliary cirrhosis (17 cases) and controls (9 cases of primary sclerosing cholangitis, 10 cases of extrahepatic biliary obstruction, 20 cases of chronic viral hepatitis C, and 18 cases of histologically normal livers). Expression of fractalkine in biliary epithelial cells (BECs) in response to cytokine treatments was examined using a human cholangiocarcinoma cell line (HuCC-T1) and human intrahepatic BEC line. The chemotaxis of CX3CR1-expressing monocytes (THP-1) toward fractalkine was assayed using chemotaxis chambers. Fractalkine messenger RNA/protein were expressed on BECs of normal and diseased bile ducts, and their expression was upregulated in injured bile ducts of primary biliary cirrhosis. CX3CR1 was expressed on infiltrating mononuclear cells in portal tracts and on CD3(+), CD4(+), and CD8(+) intraepithelial lymphocytes of injured bile ducts in primary biliary cirrhosis. Fractalkine messenger RNA expression was upregulated in two cultured BECs on treatment with lipopolysaccharide and Th1-cytokines (interleukin 1beta, interferon gamma, and tumor necrosis factor alpha). THP-1 cells showed chemotaxis toward fractalkine secreted by cultured cells. In conclusion, Th1-cytokine predominance and lipopolysaccharide in the microenvironment of injured bile ducts resulting from primary biliary cirrhosis induce the upregulation of fractalkine expression in BECs, followed by the chemoattraction of CX3CR1-expressing mononuclear cells, including CD4(+) and CD8(+) T cells, and their adhesion to BECs and the accumulation of biliary intraepithelial lymphocytes.

Aged↗

PubMed2005

Th1 cytokine-induced downregulation of PPARgamma in human biliary cells relates to cholangitis in primary biliary cirrhosis.

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is known to inhibit the production of proinflammatory cytokines. In Th1-predominant diseases, PPARgamma ligands can ameliorate clinical severity by downregulating the expression of proinflammatory cytokines. Primary biliary cirrhosis (PBC) is characterized by chronic destructive cholangitis with a Th1-predominant cytokine milieu. Unusual immune responses to infectious agents are suspected to underlie its etiopathogenesis. We examined the significance of PPARgamma in biliary inflammation in connection to PBC. To this end, we performed immunohistochemistry, quantitative polymerase chain reaction, and nuclear factor-kappaB (NF-kappaB) DNA-binding assays to clarify the intrahepatic distribution of PPARgamma and the regulation of PPARgamma by inflammatory cytokines and PPARgamma ligand in five cultured biliary cell lines including one derived from PBC liver. In liver specimens from patients with PBC, PPARgamma protein was ubiquitously expressed in intrahepatic biliary epithelium, whereas the expression of PPARgamma protein and mRNA was reduced in damaged bile ducts. PPARgamma expression in cultured cells was upregulated by interleukin-4 (IL-4; Th2-type), but downregulated by IFN-gamma (Th1-type). PPARgamma ligand negatively modulated lipopolysaccharide-induced NF-kappaB activation. Moreover, this inhibitory effect of PPARgamma ligand was attenuated by pretreatment with IFN-gamma. In conclusion, PPARgamma may be important to maintain homeostasis in the intrahepatic biliary epithelium, and its reduction in the bile ducts of PBC liver may be associated with the Th1-predominant milieu and with the development of chronic cholangitis in PBC. Immunosuppression using PPARgamma ligands may be of therapeutic benefit to attenuate biliary inflammation in PBC.

Bile Ducts↗

PubMed2003

Distinct costimulation dependent and independent autoreactive T-cell clones in primary biliary cirrhosis.

BACKGROUND & AIMS: Previous work has suggested that CD4+ CD28- or costimulation-independent T cells are increased in autoimmune diseases. In this study, we compared frequency and qualitative characteristics of autoreactive costimulation-independent or CD4+ CD28- T cells in primary biliary cirrhosis (PBC) by taking advantage of the well-defined immunodominant autoepitope of the E2 component of pyruvate dehydrogenase (PDC-E2). METHODS: We determined the frequency of costimulation-independent autoreactive T cells that respond to PDC-E2 163-176 and the frequency of CD4+ CD28- T cells. Finally, we determined the role of biliary epithelial cells (BEC) as both an antigen-presenting cell or, alternatively, as a target cell for T-cell-mediated cytotoxicity. RESULTS: The precursor frequency of costimulation-independent CD4+ T cells that respond to PDC-E2 163-176 and the frequency of CD4+ CD28- T cells were dramatically elevated in PBC. Furthermore, 2 types of T-cell clones that respond to PDC-E2 163-176 emerged from this study. One type was costimulation dependent and the other costimulation independent. Both types of clones lyse BEC in a similar effector target (E/T) ratio distribution. However, BEC did not help the proliferation of any T-cell clones. Furthermore, costimulation-independent T-cell clones do not become anergic by BEC. CONCLUSIONS: In PBC, costimulation-independent autoreactive T cells, which do not become anergic, increase and maintain the autoimmune response. In controls, although autoantigens are expressed on BEC and autoantigen-reactive T cells exist around BEC, autoantigen-reactive T cells are costimulation dependent and will become anergic and maintain peripheral tolerance.

Antigen-Presenting Cells↗

PubMed2003

Molecular mimicry of mitochondrial and nuclear autoantigens in primary biliary cirrhosis.

BACKGROUND & AIMS: The mechanism for development of primary biliary cirrhosis (PBC) remains enigmatic, but molecular mimicry has been implicated because of well-known cross-reactivity of human mitochondrial autoantigens and equivalent bacterial antigens. Virtually all patients with PBC have antimitochondrial autoantibodies (AMA), but, interestingly, approximately 50% also manifest antinuclear antibodies (ANA). METHODS: To determine whether generation of ANA are due to molecular mimicry of mitochondrial peptides, we established 6 T-cell clones selected by a peptide corresponding to the E2 subunit of mitochondrial pyruvate dehydrogenase complex and analyzed for reactivity to mimicry peptides derived from mitochondrial and nuclear autoantigens, including control sequences. RESULTS: For mitochondrial autoantigens, 1 peptide from the E2 subunit of the pyruvate dehydrogenase complex, 1 peptide from the E2 subunit of the oxo-glutarate dehydrogenase complex, 1 peptide from the E2 subunit of the branched-chain 2-oxoacid dehydrogenase complex, and 1 peptide from the E3-binding protein cross-reacted with these T-cell clones. For the nuclear autoantigens, 5 peptides from gp210 and 1 from Sp100 cross-reacted with these clones. Furthermore, 1 of 3 T-cell clones selected by recombinant gp210 protein reacted with a mimicry peptide corresponding to amino acids 188-201 of gp210, indicating that this part of the protein is a naturally processed immunodominant T-cell epitope. CONCLUSIONS: These results demonstrate molecular mimicry between mitochondrial and nuclear autoantigens in PBC and that a mimicry peptide may become an immunodominant T-cell epitope. These data have significance not only for PBC but also for the production of ANA in other disease processes.

Amino Acid Sequence↗

PubMed2003

Promiscuous T cells selected by Escherichia coli: OGDC-E2 in primary biliary cirrhosis.

The etiology of primary biliary cirrhosis (PBC) remains enigmatic. One theory that has attracted attention proposes that PBC is induced via molecular mimicry with Escherichia coli. If molecular mimicry is responsible for the immunogenic response in PBC, then T cell clones specific for E. coli antigens should stimulate and be cross-reactive with peptides specific for the human immunodominant autoepitopes. To address this issue, we developed T cell clones specific for E. coli OGDC-E2 peptide. Importantly, we demonstrate the presence of T cell clones specific for E. coli OGDC-E2 that react promiscuously with the human mitochondrial equivalents. Indeed, there was a significant increase in the liver derived T cell precursor frequency of such reactivity and such liver clones were only found in patients with PBC. In conclusion, these data suggest that PBC is a multi-hit disease involving a genetic predisposition, a mucosal response, and activation of promiscuous T cells; such activation may occur either directly from bacterial antigens, or indirectly through chemically-modified bacterial antigens. Dissection of the mechanisms involved will lead not only to understanding the immunogenetic basis of PBC, but likely its pathogenic etiology.

Acyltransferases↗