High levels of TNF, soluble TNF receptors, soluble ICAM-1, and IFN-gamma, but low levels of IL-5, are associated with hepatosplenic disease in human schistosomiasis mansoni.
Mwatha JK. Kimani G. Kamau T. Mbugua GG. Ouma JH. Mumo J. Fulford AJ. Jones FM. Butterworth AE. Roberts MB. Dunne DW.
Kenya Medical Research Institute, Division of Vector Borne Diseases, Nairobi.
In a case-control study based in two areas of Kenya, hepatosplenic schistosomiasis mansoni was shown to be linked with low levels of IL-5 and with correspondingly high IFN-gamma, TNF, and circulating soluble TNF receptor I (sTNFR-I), sTNFR-II, and sICAM-1. PBMC from the hepatosplenic cases responded to in vitro Ag stimulation with significantly higher levels of IFN-gamma and TNF, but lower levels of IL-5, compared with nonhepatosplenic controls matched for age and infection intensity. Most of these correlations were confounded by differences between geographical areas. However, principle component analysis identified a high IFN-gamma and TNF, and low IL-5 axis in the data as the first principle component; this was significantly associated with hepatosplenomegaly (p < 0.0005) even after controlling for area. High plasma levels of sTNFR-I (p < 0.001), sTNFR-II, (p < 0.0001), and sICAM-1 (p < 0.009) were also significantly associated with hepatosplenomegaly, independently of area, in the case of the soluble forms of both TNF receptors. These parameters were negatively related to IL-5. These results suggest that proinflammatory cytokines are involved in the hepatosplenic disease process in infected individuals who have low anti-inflammatory Th2 responses and that sTNFR may be a useful circulating marker for this disease process, perhaps reflecting the level of TNF activity in hepatic tissues.
Structural dichotomy of staphylococcal enterotoxin C superantigens leading to MHC class II-independent activation of T lymphocytes.
Lamphear JG. Bohach GA. Rich RR.
Department of Microbiology and Immunology, Baylor College of Medicine, Houston, TX 77030, USA.
We have recently characterized an MHC class II-deficient human cell line, SW480, that supports the proliferation of purified human T cells in the presence of the staphylococcal enterotoxin and superantigen SEC1, but not the closely related isotypes SEC2 or SEC3. We now investigate the structural basis of this dichotomy and explore possible mechanisms that may account for it. Differences in activity between SEC1 and SEC2 were not attributable to differences in biochemical modification, to differences in Vbeta specificity, or to the potential to induce anergy. SEC2 inhibited SEC1-mediated T cell activation in the presence of SW480 cells, suggesting that SEC2 could compete with SEC1 for binding to the TCR but was unable to productively signal through the TCR. Utilizing a panel of hybrid enterotoxins we identified specific amino acids near the NH2-terminus of SEC1 that abrogated MHC class II-independent T cell activation, yet did not alter potency in the presence of class II+ APC. These residues mapped to the putative TCR binding domain of SEC1, and suggest that subtle differences in TCR binding affinity or the topology of the SEC1-TCR interaction can compensate for the lack of MHC class II and hence promote T cell proliferation.
Activation of IL-8 gene expression by Helicobacter pylori is regulated by transcription factor nuclear factor-kappa B in gastric epithelial cells.
Sharma SA. Tummuru MK. Blaser MJ. Kerr LD.
Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
In vivo, gastric infection with Helicobacter pylori leads to substantial production of the inflammatory cytokines IL-1, IL-6, TNF-alpha, and IL-8. H. pylori strains that contain the cag pathogenicity island (cag+) and are associated with ulceration and gastric carcinoma induce greater cytokine production than cag- strains. Expression of these cytokines is often regulated by the transcription factor complex, nuclear factor-kappa B (NF-kappa B) through kappa B-binding elements in the enhancer/promoter regions of their genes. We report that more virulent cag+ H. pylori strains induce increased NF-kappa B-DNA binding activity, which elevates IL-8 expression in AGS gastric epithelial cells. The cag+ H. pylori strains induce significant stimulation of IL-8 promoter-driven reporter activity, while cag- strains do not. Furthermore, mutation of specific genes within the cag island (picA1 and picB) ablates enhanced NF-kappa B activation and IL-8 transcription. Increased IL-8 expression is inhibited by mutation in either the NF-kappa B or NF-IL-6 binding element. The cag+ strains, compared with the cag- strains, induce enhanced nuclear localization of a RelA-containing NF-kappa B binding complex, but no increase in NF-IL-6 binding activity. These studies demonstrate that the ability of different types of H. pylori strains to activate NF-kappa B correlates with their ability to induce IL-8 transcription and indicate a mechanism for the heightened inflammatory response seen in subjects infected with cag+ H. pylori strains.
Clonal analysis of intrahepatic B cells from HCV-infected patients with and without mixed cryoglobulinemia.
Sansonno D. De Vita S. Iacobelli AR. Cornacchiulo V. Boiocchi M. Dammacco F.
Department of Biomedical Sciences and Human Oncology, University of Bari Medical School, Italy.
Clonal rearrangements of Ig heavy chain (IgH) genes and hepatitis C virus (HCV) genomic sequences were assayed on intrahepatic B lymphocytes isolated from HCV chronically infected patients with and without type II mixed cryoglobulinemia (MC). Liver tissue samples from eight patients with and nine without MC were subjected to routine histologic studies, immunophenotyping, and genotypic analysis including IgH V-D-J region gene rearrangements by PCR. RT-PCR, signal amplification by branched DNA assay, and in situ hybridization technique were used to detect and quantitate HCV RNA genomic sequences in selected B cells purified from each tissue sample. Although HCV infection of intrahepatic B cells was shown in all patients both with and without MC, frank B cell monoclonal and oligoclonal patterns were found in only three and four patients with MC, respectively. No monoclonal profile was seen in the noncryoglobulinemic patients, whereas an oligoclonal profile was demonstrated in four of them. No clonalities were shown in HCV-unrelated patients matched for age and severity of liver disease. No obvious difference in HCV genotype distribution was found in relation to the clonal expansion profile. Noncryoglobulinemic patients showing clonal expansion in liver tissue had higher titers of serum rheumatoid factor (RF). Spontaneous production of RF was shown in cell cultures of intrahepatic B cells, suggesting their persistent stimulation in vivo. These data indicate that HCV infection of B cells and B cell clonal expansions occur in the liver microenvironment and preferentially involve RF-producing cells.
Intercellular adhesion molecule-1 and leukocyte function-associated antigen-3 provide costimulation for superantigen-induced T lymphocyte proliferation in the absence of a specific presenting molecule.
Lamphear JG. Stevens KR. Rich RR.
Department of Microbiology, Baylor College of Medicine, Houston, TX 77030, USA.
Bacterial superantigens can bind TCR in the absence of MHC class II molecules and activate T lymphocytes when cocultured with certain class II-deficient accessory cells. It has not been determined, however, whether these accessory cells provide direct costimulation to the T cell or serve to present superantigens via a nonconventional ligand. We have identified a human adenocarcinoma cell line, SW480, that assists in the activation of human T cells by the staphylococcal enterotoxins B (SEB), C1 (SEC1), and D (SED), but not SEA, SEC2, SEC3, or SEE. SW480 cells did not express class II molecules, and anti-class II mAbs did not inhibit T cell proliferation, supporting the hypothesis that class II is not absolutely required for enterotoxin-mediated T cell activation. The TCR Vbeta profile of T cells stimulated by SEB plus SW480 cells was similar to that of T cells stimulated by SEB plus class II+ APC, indicating that TCR-SEB interactions were preserved in the absence of class II molecules. Binding studies failed to detect specific association of SEB with SW480 cells, suggesting that SW480 cells do not express receptors for enterotoxin. SEB coupled to beads, however, stimulated T cell proliferation, but only in the presence of SW480 cells. SW480 cells express both ICAM-1 and LFA-3 molecules, and the addition of Abs to these receptors inhibited T cell proliferation. These findings support a model in which certain enterotoxins engage the TCR independent of MHC class II or other specific presenting molecules and induce T cell proliferation with signals provided by nonconventional accessory cells.
Vascular adhesion protein-1 and ICAM-1 support the adhesion of tumor-infiltrating lymphocytes to tumor endothelium in human hepatocellular carcinoma.
Yoong KF. McNab G. Hubscher SG. Adams DH.
Liver Research Laboratories, Queen Elizabeth Hospital, Birmingham, United Kingdom.
T cell-mediated mechanisms are important in the defense against solid organ tumors. Why some tumors are more heavily infiltrated by T cells than others is poorly understood but is likely to depend upon adhesive interactions between circulating lymphocytes and tumor endothelium. In support of this hypothesis, the present study shows that primary human hepatocellular carcinomas (HCC) are more heavily infiltrated with T cells than colorectal hepatic metastases (CHM), and that their tumor vessels express high levels of several adhesion molecules. In HCC, an intense T cell infiltrate is observed within the tumor associated with strong expression of ICAM-1 and vascular adhesion protein-1 (VAP-1) on tumor endothelium. In contrast, fewer T cells infiltrated CHM and these tumors have little ICAM-1 and no detectable VAP-1 or VCAM-1 on tumor endothelium. T cells infiltrating both tumors are LFA-1 and very late Ag (VLA)-4 high. In vitro tissue-binding studies demonstrated that T cells bound readily to tumor endothelium in HCC, and Abs to ICAM-1, VAP-1, and to a lesser extent VCAM-1 could inhibit this binding. VAP-1 supported sialic acid-dependent adhesion under shear stress, suggesting that VAP-1 and ICAM-1 mediate, respectively, tethering and firm adhesion. In contrast, very few T cells bound to tumor vessels in CHM. Thus our data suggest that the VAP-1/VAP-1 receptor and ICAM-1/LFA-1 pathways are important in the recruitment of T cells to HCC. The strong expression of VAP-1 on tumor endothelium distinguishes HCC from CHM and supports our previous hypothesis that VAP-1 is an important hepatic endothelial adhesion molecule.
Liver-derived CTL in hepatitis C virus infection: breadth and specificity of responses in a cohort of persons with chronic infection.
Wong DK. Dudley DD. Afdhal NH. Dienstag J. Rice CM. Wang L. Houghton M. Walker BD. Koziel MJ.
Infectious Diseases Unit, Massachusetts General Hospital, Boston 02114, USA. WongD@Helix.MGH.Harvard.edu
Hepatitis C virus (HCV)-specific CTL have been found within the inflammatory infiltrate of the liver of chronically infected individuals, but the breadth and specificity of the CTL response in relation to viral load are less well characterized. In this study, we analyzed the intrahepatic CTL response in liver biopsy specimens from 44 chronically infected subjects. Liver-infiltrating lymphocytes were expanded polyclonally in bulk cultures, and multiple clones were derived by limiting dilution. HCV-specific CTL responses directed at genotype 1a structural proteins were assessed in all subjects, and 22 subjects were tested more comprehensively using vectors expressing all structural and nonstructural HCV Ags. CTL responses were further characterized to determine the HLA restriction and optimal epitopes recognized. In those persons screened for recognition of all HCV Ags, HLA class I-restricted CTL were detected in 45%. Nineteen different CTL epitopes were identified, which were distributed throughout the genome; only one epitope was targeted by more than one person. In those persons with CTL responses, the breadth of response ranged from one to five epitopes. There was no correlation between the presence of a detectable CTL response and viral load. These results indicate considerable heterogeneity in detectable HCV-specific CTL responses in chronically infected persons. The mechanisms by which HCV persists during chronic infection remain to be clarified.
The Fas counterattack in vivo: apoptotic depletion of tumor-infiltrating lymphocytes associated with Fas ligand expression by human esophageal carcinoma.
Bennett MW. O'Connell J. O'Sullivan GC. Brady C. Roche D. Collins JK. Shanahan F.
Department of Medicine, Cork University Hospital, Ireland.
Various cancer cell lines express Fas ligand (FasL) and can kill lymphoid cells by Fas-mediated apoptosis in vitro. FasL expression has been demonstrated in several human malignancies in vivo. We sought to determine whether human esophageal carcinomas express FasL, and whether FasL expression is associated with increased apoptosis of tumor-infiltrating lymphocytes (TIL) in vivo, thereby contributing to the immune privilege of the tumor. Using in situ hybridization and immunohistochemistry, respectively, FasL mRNA and protein were colocalized to neoplastic esophageal epithelial cells in all esophageal carcinomas (squamous, n = 6; adenocarcinoma, n = 2). The Extent of FasL expression was variable, with both FasL-positive and FasL-negative neoplastic regions occurring within tumors. TIL were detected by immunohistochemical staining for the leukocyte common Ag, CD45. FasL expression was associated with a mean fourfold depletion of TIL when compared with FasL-negative areas within the same tumors (range 1.6- to 12-fold, n = 6,p < 0.05). Cell death of TIL was detected by dual staining of CD45 (immunohistochemistry) and DNA strand breaks (TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling). There was a mean twofold increase in detectable cell death among TIL in FasL-positive areas compared with FasL-negative areas (range 1.6- to 2.4-fold, n = 6, p < 0.05). In conclusion, we demonstrate a statistically significant, quantitative reduction of TIL concomitant with significantly increased TIL apoptosis within FasL-expressing areas of esophageal tumors. Our findings suggest Fas-mediated apoptotic depletion of TIL in response to FasL expression by esophageal cancers, and provide the first direct, quantitative evidence to support the Fas counterattack as a mechanism of immune privilege in vivo in human cancer.