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Biomedical subjects

G Gerken

Publications and source records attributed to G Gerken.

At least 199 records · Page 11Linked to original sources
PubMed1993

Low frequency of cytotoxic liver-infiltrating T lymphocytes specific for endogenous processed surface and core proteins in chronic hepatitis B.

To investigate the role of hepatitis B virus (HBV)-specific CD8+ T cells in chronic hepatitis B, the lytic activity of peripheral blood mononuclear cells (PBMC) and liver-infiltrating T cell clones and cytotoxic T cell (CTL) lines stimulated by recombinant vaccinia virus-infected cells were analyzed. Autologous and allogeneic Epstein-Barr virus-transformed B cells infected with vaccinia vectors (VAC) that contain sequences of the surface (S), secretory core (E), cytoplasmatic core (C) VAC antigen of HBV, or the wild-type (WT) VAC served as target cells. ELISA and immunoblotting showed HBV antigen expression in infected cells. Neither PBMC nor C- or E-VAC-stimulated CTL lines showed specific lytic activity. However, S-VAC stimulated blood- and liver-derived CTL from 2 patients with hepatitis B lysed autologous S-VAC but not WT-VAC-infected target cells. One of 158 CD8+ T cell clones from 6 patients with active hepatitis B lysed autologous, but not allogeneic, S-VAC-infected targets. Thus, CTL are present among liver-infiltrating T cells in chronic hepatitis B that recognize endogenously processed hepatitis B surface antigen but not HBc or HBe antigen. The lack of core-specific CTL may contribute to failure in virus elimination in chronic inflammation.

B-Lymphocytes↗
PubMed1993

[Infiltrating T-cells in primary biliary cirrhosis recognize mitochondrial epitopes].

The primary biliary cirrhosis (PBC) is characterized by lymphoid infiltrates in the portal tracts of the liver and occurrence of antimitochondrial autoantibodies (AMA) in serum directed against the pyruvate dehydrogenase complex or other enzyme complexes that are located on the inner mitochondrial membranes. The destruction of the biliary tracts is thought to be mediated by autoreactive liver infiltrating T-cells. In this study we demonstrate the reactivity of peripheral and liver-infiltrating T-cells against a crude preparation of human liver subcellular fractions measured by the tritium-thymidine uptake. Peripheral blood mononuclear cells (PBMC) from 13 of 15 patients with PBC and from 3 of 9 patients with chronic autoimmune hepatitis recognized human liver mitoplasts, i.e. mitochondria depleted of their outer membranes. PBMC from patients with chronic viral hepatitis B and C or with extrahepatic cholestatic icterus and PBMC from healthy controls did not recognize this antigen. Monoclonal antibodies against HLA-class II molecules blocked this proliferative response. Clonal analysis of 115 liver-infiltrating T-cells derived from two diagnostic liver biopsies of patients with PBC revealed a predominance of activated CD4+CD8- T helper cells. Six CD4- positive T-cell clones were reactive to the HLM preparation when the antigen was presented by autologous B cell lines. MAb against HLA-class II or HLA-DR inhibited the response whereas mAb against HLA-DP did not. These clones did not respond to other subcellular fractions of human liver tissue. We conclude that among liver-infiltrating T-cells in PBC autoreactive T-cells exist that recognize some epitopes on the inner mitochondrial membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigen-Presenting Cells↗
PubMed1993

Lack of surface expression for the B-cell autoepitope of cytochrome P450 IID6 evidenced by flow cytometry.

The major target antigen of LKM-1 autoantibodies in chronic active hepatitis is cytochrome P450 IID6. The role of LKM-1 autoantibodies in the pathogenesis of the disease is not clear. A crucial point is the expression of the target epitope on the hepatocyte membrane. Cultured rat hepatocytes were used in this study. Time dependent analysis of cytochrome P450 IID6 specific RNA-level revealed a constant decrease in culture. A high amount of the specific RNA-level was present after culturing the hepatocytes for 24 hours at the time of the membrane studies. To investigate membrane surface expression, we used recombinant human cytochrome P450 IID6 to affinity purify the specific autoantibody from patients sera. Indirect immunofluorescence studies and flow cytometry analysis were performed with viable, unfixed rat hepatocytes. As positive control, a monoclonal antibody against rat MHC class I antigens was used. More than 85% of viable hepatocytes showed a positive membrane staining after the incubation with the monoclonal antibody to MHC class I antigens. Affinity purified monospecific LKM-1 autoantibody, sera from control subjects and from patients with liver diseases showed a membrane staining of less than 10%. Thus, no significant expression of the B cell autoepitope of LKM-1 antigen was found on the plasma membrane of viable hepatocytes with the methods applied.

Antigens, Surface↗
PubMed1992

Anti-GOR and hepatitis C virus in autoimmune liver diseases.

Anti-GOR is an autoantibody found in hepatitis C virus (HCV) infection. We have studied the specificity of this antibody for HCV infection in various groups of autoimmune liver diseases. Anti-HCV was detected by a second generation HCV enzyme-linked immunosorbent assay in 14 of 29 patients with liver-kidney-microsomal (LKM-1) -antibody-positive autoimmune hepatitis type 2 and in all 6 control patients with HCV-RNA-positive chronic hepatitis C. Anti-HCV was not found in those with antinuclear-antibody-positive autoimmune hepatitis type 1 (10 patients), with soluble-liver-protein-antibody-positive autoimmune hepatitis type 3 (8), with primary biliary cirrhosis (9), with systemic lupus erythematosus (SLE) (10), or in healthy controls (13). Anti-GOR was detected in 11 of 14 patients with autoimmune hepatitis type 2 who were all positive for anti-HCV but only in 1 of 15 LKM-1 patients who were negative for anti-HCV. We did not find anti-GOR in any other group of autoimmune liver disease, SLE, or control sera, but this antibody was detected in 3 of 6 patients with chronic hepatitis C. Autoimmune hepatitis type 2 patients who were anti-GOR positive and anti-HCV positive were less likely to be female, were older (p less than 0.001), and had lower LKM-1 antibody titres (p less than 0.001), lower disease activity, and responded less effectively to immuno- suppression than did those who were anti-HCV negative/anti-GOR negative. The findings show that anti-GOR reflects HCV-specific autoimmunity. HCV seems to induce autoimmunity to both GOR (an HCV-specific autoepitope) and LKM-1 (an epitope that is also recognised by autoimmune hepatitis sera of a different cause). Anti-GOR and LKM-1 antibodies contribute to a better differentiation of chronic hepatitis, a finding that has therapeutic implications.

Adolescent↗
PubMed1992

Regulation of cytochrome P450 IID by acute phase mediators in C3H/HeJ mice.

Cytochrome P450 IID6 is a drug metabolizing enzyme and the major target antigen in LKM-1 antibody positive chronic active hepatitis. The histological hallmark of chronic active hepatitis is a lymphocytic infiltrate in the liver. It is unknown whether and how cytokines produced and secreted by these tissue infiltrating mononuclear cells regulate the cellular expression of cytochrome P450 IID6. To study the effect of interleukin 1, tumor necrosis factor and interleukin 6 on the hepatocellular RNA expression of cytochrome P450 IID, we injected each of the cytokines in C3H/HeJ mice. We found a time-dependent suppression of the cytochrome in the liver. Six hours after the intraperitoneal injection of 0.5 micrograms interleukin 1 beta the specific RNA-expression was reduced to 25% of the original level. A similar reduction was found after the injection of 2 micrograms tumor necrosis factor alpha. A mild suppression to 65% of the original level was seen six hours following the dose of 100 ng interleukin 6. Our studies show how immune mediators can change the expression of an autoantigen. Further studies in the human system are necessary to estimate this regulation for the elimination of drugs and in LKM-1 antibody positive chronic active hepatitis.

Animals↗
PubMed1992

Clinical significance of the polymerase chain reaction (PCR) assay in chronic HBV carriers.

PCR was evaluated as a clinical tool for use in accurate identification of the specific etiologic agent in chronic HBV carriers. The method was found to be valuable in diagnosis and for monitoring therapy, as well as for elucidation of genotypic variants of HBV in chronic HBV cases. By this means an HBV defective variant with alterations in the preS1/preS2 sequence was detected and is consequently described here.

Asia, Southeastern↗
PubMed1992

Hepatitis C virus (HCV) and autoimmune liver diseases.

Anti-HCV tests were positive in 18-45% of sera from patients with autoimmune chronic active hepatitis. High gammaglobulin levels may result in false positive results, however, some sera show true positivity. PCR testing of such sera is necessary in order to determine whether HCV is directly involved in specific forms of the disease.

Antigens, Viral↗
PubMed1992

In vitro secretion of specific antimitochondrial antibodies in primary biliary cirrhosis.

Antimitochondrial antibodies are present in the serum of virtually all patients with primary biliary cirrhosis. They have a well-defined antigen reactivity that is diagnostic for the disease. The role of these autoantibodies in the disease process remains to be defined. In this study we show that antimitochondrial antibodies can be produced in vitro by peripheral blood lymphocytes, that the cells producing antimitochondrial antibodies are present in the peripheral blood in a high frequency and seem to be maximally activated. Stimulation with pokeweed mitogen did not augment the in vitro production of antimitochondrial antibodies in patients nor did it induce the production of these antibodies by control lymphocytes. Thus, antimitochondrial antibodies are not simply an expression of polyclonal B-cell stimulation. The high frequency of maximally activated B-cells producing antimitochondrial antibodies suggests active antigenic stimulation.

Antibody Specificity↗
PubMed1991

HLA DRw8 and complement C4 deficiency as risk factors in primary biliary cirrhosis.

HLA class I, II, and III alleles were investigated in 25 consecutive unrelated German patients with primary biliary cirrhosis and in two families with two primary biliary cirrhosis patients in each. In primary biliary cirrhosis patients, HLA class I antigens did not differ significantly from in health controls. For HLA class II antigens, a highly significant increase of HLA DRw8 was found in patients with primary biliary cirrhosis compared with controls. Thirty-six percent vs. 3.6% were DRw8 positive [relative risk = 15.28; P (corrected) = 0.00013]. The genetic typing of HLA class III alleles revealed an increased incidence for C4AQ0 alleles [72% vs. 34.5%, relative risk = 4.89: P (corrected) = 0.0056]. A highly significant proportion of primary biliary cirrhosis patients carrying both DRw8 and C4A-Q0 alleles (relative risk = 183.75; P = 9.7 x 10(-7)) were found. In one family, a mother and her daughter had primary biliary cirrhosis, both sharing the major histocompatibility complex haplotype HLA-A1, -B8, -DR3, -C4AQ0B1. In the other family, two sisters with primary biliary cirrhosis shared the major histocompatibility complex haplotype HLA-A24, -B8, -DRw8, -C4A4B2. These studies contribute to the further elucidation of the immunogenetic background of primary biliary cirrhosis.

Alleles↗
PubMed1991

Hepatitis B defective virus with rearrangements in the preS gene during chronic HBV infection.

We have found a defective form of HBV2 in a HBsAg- and anti-HBe-positive patient with liver cancer. Viral deletions were identified in the preS coding region using PCR. The presence of deleted HBV forms was observed in serum, PBMC, and liver samples. After sequencing 12 clones were analyzed (subtype adr). In 9 out of 12 clones a 183-bp in-frame deletion was recorded in the preS1 region (2995 to 3177). Three out of 9 clones also yielded rearrangements of the preS2 N-terminal part. Four out of 9 showed numerous point mutations in the preS1 and preS2 sequence. In addition, 3 out of 12 clones, which did not show the 183-bp preS1 deletion were found to have small deletions and insertions in the same part of the preS1 gene. Immunological mapping using monoclonal anti-preS antibodies showed loss of preS epitopes located at the 3'-part of preS1 and the 5'-part of preS2. On the other hand, epitopes mapped to the 5'-part of preS1 and 3' of preS2 were conserved. PBMC were also tested and solely PCR showed the major form of defective HBV with preS1 183-bp deletion. However, viral deletions in the preS gene eliminated the preS2 promotor region and B- and T-cell recognition sites. In contrast to this, the preS1 binding site to hepatocytes was conserved. Therefore, such deletions would potentially lead to an impairment in viral clearance without affecting viral penetration in liver cells, possibly accounting for chronic HBV infection.

Adult↗
PubMed1991

Hepatitis B defective virus with rearrangements in the preS gene during HBV chronic infection.

We have found a defective form of hepatitis B in an anti-HBe positive chronic HBsAg carrier with liver cancer (HCC). Viral deletions were identified in the preS coding region using PCR and sequencing. The presence of deleted HBV forms was observed in serum, PBMC, and liver tissue. To conclude, rearrangements and deletions in the preS gene would potentially lead to an impairment in viral clearance without affecting viral penetration in liver cells, possibly accounting for chronic HBV infection.

Adult↗
PubMed1991

Assay of hepatitis B virus DNA by polymerase chain reaction and its relationship to pre-S- and S-encoded viral surface antigens.

The polymerase chain reaction was evaluated as a diagnostic tool in 72 chronic hepatitis B virus carriers. Hepatitis B virus DNA was detectable in the serum of HBsAg-positive virus carriers using aliquots as small as 100 al. The detection limit for cloned hepatitis B virus DNA was 100 ag. Primer pairs for different regions of the HBV genome resulted in different sensitivity. Detection of the amplified hepatitis B virus DNA by Southern blotting and subsequent scintillation counting or densitometry allowed a semiquantitative assay. Using several primer pairs in parallel for optimal detection, all HBeAg-positive HBsAg carriers, 80% of HBe antibody-positive symptomatic HBsAg carriers and 57% of asymptomatic HBe antibody-positive HBsAg carriers were found to have hepatitis B virus DNA in the serum. During antiviral therapy hepatitis B virus DNA disappeared by the polymerase chain reaction assay in patients who became HBeAg negative, but polymerase chain reaction detected a relapse earlier than did the conventional dot blot. Pre-S antigens were assayed in serum and liver samples from most chronic carriers by enzyme-linked immunosorbent assay and/or immunoblot. Although most viremic carriers were strongly positive for pre-S1 and pre-S2 antigens, some hepatitis B virus DNA-positive HBsAg carriers did not have detectable pre-S antigens, and vice versa. Our data show that assay of hepatitis B virus DNA in the serum by polymerase chain reaction is by far more proficient than by dot blot and that it cannot be replaced by serological assays of HBeAg or pre-S antigen.

Base Sequence↗