Molecular chaperones in the processing and presentation of antigen to helper T cells

Helper T lymphocytes recognize peptide fragments of antigen bound to Major Histocompatibility Complex (MHC) class II molecules on the surfaces of antigen presenting cells (APC). Antigen processing involves internalization of the antigen into an acidic compartment where the antigen is degraded and the resulting peptide fragments of the antigen are bound to MHC class II molecules and the complexes subsequently displayed at the APC surface. Thus, antigen processing represents a complex, intracellular assembly process which may, like many intracellular protein folding and assembly processes, require the function of molecular chaperones. This contribution focuses on the evidence which suggests that members of the heat shock protein family of molecular chaperones play a role in this pathway.     

cGMP-phosphodiesterase 6, transducin and Wnt5a/Frizzled-2-signaling control cGMP and Ca2+ homeostasis in melanoma cells

Malignant melanoma is one of the most aggressive human neoplasms which develop from the malignant transformation of normal epithelial melanocytes and share the lineage with retinal cells. cGMP-phosphodiesterase 6 (PDE6) is one of the cancer-retina antigens newly identified in melanoma cells. Normally, PDE6 hydrolyzes the photoreceptor second messenger cGMP allowing the visual signal transduction in photoreceptor cells. cGMP also play an important signaling role in stimulating melanogenesis in human melanocytes. Here, we present evidence that PDE6 is a key enzyme regulating the cGMP metabolism in melanoma cells. Decrease in intracellular cGMP leads to calcium accumulation in melanoma cells. In these cells, cGMP-phosphodiesterase 6 can be activated by another cancer-retina antigen, transducin, through Wnt5a–Frizzled-2 cascade, which leads to a lowering of cGMP and an increase in intracellular calcium mobilization. Thus, the aberrant expression of PDE6 may control cGMP metabolism and calcium homeostasis in melanoma cells.     

Formation of the B cell synapse: retention or recruitment?

Interaction of B cells with membrane antigen results in the formation of the B cell synapse: the B cell receptor (BCR) and antigen concentrate in the contact zone while CD45/B220 and the phosphatase SHP-1 are excluded. This study shows that, unlike in T cells, synapse formation does not require active transport processes (while subsequent antigen extraction and IgM downregulation do). The synapse architecture depends on the available protein ligands in the contact zone. Thus Syk, IgM and Fc receptor accumulation require the presence of ITAM-bearing BCRs, membrane antigen and membrane (IgG-containing) immune complexes, respectively. Remarkably, non-bound proteins are frequently not only homogeneously distributed but excluded from the contact zone. These results suggest that proteins mainly reach the contact zone by undirected diffusion, and in order not to be expelled by molecular crowding they require capture by and fixation to a binding protein.Received 25 August 2004; received after revision 2 November 2004; accepted 17 November 2004     

Einfluß antianaphylaktisch wirkender Stoffe auf die Antikörperproduktion

Summary To produce antisera of high antibody concentration animals after sensitization with protein have been reinjected with lethal doses of the antigen, protected against the shock-effect by substances with antihistamin properties (as example Antistin). The antibody concentration was considerably higher in these animals as in the other non-protected group reinjected with the highest tolerated antigen dosage.     

Phenotypic expression of colon polymorphic antigens (WZ) in human colon adenocarcinomas]

Human colon adenocarcinomas from 52 patients were investigated for the presence of the colon polymorphic antigens WZ. The patients were typed for their WZ phenotype, using the immunofluorescence method on non tumoral colon mucosa sections: 27 patients were found W+ Z+, 18 W- Z+, and 7 W- Z-. The tumors were tested for the presence of the WZ phenotypes, using the immunofluorescence method and a radio-immunoassay. The WZ phenotypes were not expressed in the non secreting tumors, whatever the patient's phenotype. They were expressed in the secreting tumors and had the same phenotype as found in the corresponding normal mucosa. The WZ phenotypes were present in human developed into "nude" Mice inoculated either with differentiated colon carcinomas, or with a human colon carcinoma cell line (HT-29).     

Cytotoxicity of human peripheral blood T-lymphocyte clones activated by hepatitis B virus surface antigen

Summary The present studies examined the cytotoxic activities of peripheral blood lymphocytes (PBL) from volunteers with (sero-positive) and without (sero-negative) circulating antibodies to hepatitis B virus surface antigen before and 30 days after vaccination with hepatitis B virus surface antigen (HBsAg). Long-term culture of monospecific hepatitis B surface (HBsAg)-responsive T-lymphocytes were isolated and grown in large numbers. The mechanism of T-cell mediated cytolysis, and the identification of the carbohydrate determinants on the surface of these effector cells responsible for the killing effect, are being examined.     

Cytotoxicity of human peripheral blood T-lymphocyte clones activated by hepatitis B virus surface antigen

The present studies examined the cytotoxic activities of peripheral blood lymphocytes (PBL) from volunteers with (sero-positive) and without (sero-negative) circulating antibodies to hepatitis B virus surface antigen before and 30 days after vaccination with hepatitis B virus surface antigen (HBsAg). Long-term culture of monospecific hepatitis B surface (HBsAg)-responsive T-lymphocytes were isolated and grown in large numbers. The mechanism of T-cell mediated cytolysis, and the identification of the carbohydrate determinants on the surface of these effector cells responsible for the killing effect, are being examined.     

Identification of proteins in human prostate tumor material by two-dimensional gel electrophoresis and mass spectrometry

Protein patterns in cells collected from benign prostatic tissues and prostate carcinomas were analyzed using two-dimensional polyacrylamide gel electrophoresis and mass spectrometry. Polypeptide expression was evaluated by computer-assisted image analysis (PDQUEST). Proteins expressed by prostate tumors were identified via in-gel digestion and subsequent matrix-assisted laser desorption/ionization mass spectrometry. In addition to cytoskeletal and mitochondrial proteins, a 40-kDa protein was identified as prostatic acid phosphatase (PAP). PAP expression decreased approximately twofold between benign and malignant tissue. Increased expression of heat shock protein 70 and decreased expression of tropomyosin 1 were also observed in the malignant tissue. The analysis of prostate material by two-dimensional gel electrophoresis and mass spectrometry shows that particular proteins are of interest as markers of disease. Received 18 December 2000; accepted 4 January 2001     

HLA phenotypes in patients surviving a long time after immunotherapy with BCG for acute childhood lymphoblastic leukemia. Arguments in favor of the existance of a gene for immune response in human leukemia]

HLA phenotypes of 13 patients surviving in lasting first remission over 6 years after BCG immunotherapy for acute childhood lymphoblastic leukaemia (ALL) were compared to phenotypes of normal subjects and of surviving ALL patients treated exclusively with chemotherapy. Among the BCG-treated patients, the frequency of the antigen HLA-BW 17 was 46.1% vs 7.3% in healthy controls (p less than 0.001) and the frequency of the antigen HLA-AW 33 was 30.8% vs 1.2% (p less than 0.001). 9 patients possessed at least one of these two antigens (69.2% vs 8% in controls p less than 0.001). Phenotypes of the chemotherapy-treated patients did not differ significantly from controls. These results suggest the existence in humans of HLA-linked genes which are involved in the response to BCG immunotherapy in ALL.     

Resistance of in vivo-selected spontaneously transformed cells and Rous sarcoma virus-transformed cells to macrophage-mediated cytotoxicity.

The cytotoxic activity (CTA) of activated peritoneal macrophages (MP) on variant lines of Syrian hamster embryo (HE) cells of differing malignant characteristics was studied. The target cells were a line of low-malignant cells resulting from spontaneous transformation of HE cells in vitro (STHE strain), and malignant variants selected from them in vivo (STHE-LM-4, STHE-LM-8, and STHE-75/18 strains). In addition, we used cells of the HET-SR-1 strain; these are HE cells transformed in vitro by a tumorigenic Rous sarcoma virus (Schmidt-Ruppin strain, RSV-SR), or the TU-SR strain induced by RSV-SR in vivo. Thioglycollate-elicited peritoneal MP from Syrian hamsters were activated in vitro with bacterial levan, LPS or MDP and used as effector cells. MP-mediated cytolysis was determined by means of a 42-h radioactivity release assay with 3H-thymidine-labeled target cells. We found that only the parental STHE cells were susceptible towards fully-activated MP-mediated CTA. All three of the in vivo-selected malignant variants of the STHE cell sublines, as well as the tumorigenic RSV-SR transformants, were resistant to cytolysis by activated MP. Non-activated thioglycollate-elicited MP did not lyse any of the tumor cells studied.     

Resistance of in vivo-selected spontaneously transformed cells and Rous sarcoma virus-transformed cells to macrophage-mediated cytotoxicity

The cytotoxic activity (CTA) of activated peritoneal macrophages (MP) on variant lines of Syrian hamster embryo (HE) cells of differing malignant characteristics was studied. The target cells were a line of low-malignant cells resulting from spontaneous transformation of HE cells in vitro (STHE strain), and malignant variants selected from them in vivo (STHE-LM-4, STHE-LM-8, and STHE-75/18 strains). In addition, we used cells of the HET-SR-1 strain; these are HE cells transformed in vitro by a tumorigenic Rous sarcoma virus (Schmidt-Ruppin strain, RSV-SR), or the TU-SR strain induced by RSV-SR in vivo. Thioglycollate-elicited peritoneal MP from Syrian hamsters were activated in vitro with bacterial levan, LPS or MDP and used as effector cells. MP-mediated cytolysis was determined by means of a 42-h radioactivity release assay with³H-thymidine-labeled target cells. We found that only the parental STHE cells were susceptible towards fully-activated MP-mediated CTA. All three of the in vivo-selected malignant variants of the STHE cell sublines, as well as the tumorigenic RSV-SR transformants, were resistant to cytolysis by activated MP. Non-activated thioglycollate-elicited MP did not lyse any of the tumor cells studied.     

Chemotherapy and immunotherapy of malignant glioma: molecular mechanisms and clinical perspectives

Despite the considerable progress in modern tumor therapy, the prognosis for patients with glioblastoma, the most frequent malignant brain tumor, has not been substantially improved. Although cytoreductive surgery and radiotherapy are the mainstays of treatment for malignant glioma at present, novel cytotoxic drugs and immunotherapeutic approaches hold great promise as effective weapons against these malignancies. Thus, great efforts are being made to enhance antitumoral efficacy by combining various cytotoxic agents, by novel routes of drug administration, or by combining anticancer drugs and immune modulators. Immunotherapeutic approaches include cytotoxic cytokines, targeted antibodies, and vaccination strategies. However, the success of most of these experimental therapies is prevented by the marked molecular resistance of glioma cells to diverse cytotoxic agents or by glioma-associated immunosuppression. One promising experimental strategy to target glioma is the employment of death ligands such as CD95 (Fas/Apo1) ligand or Apo2 ligand (TRAIL). Specific proapoptotic approaches may overcome many of the obvious obstacles to a satisfactory management of malignant brain tumors. Received 8 March 1999; received after revision 27 May 1999; accepted 14 June 1999     

Biology of HLA-G in cancer: a candidate molecule for therapeutic intervention?

Although the expression of the non-classical HLA class I molecule HLA-G was first reported to be restricted to the fetal–maternal interface on the extravillous cytotrophoblasts, the distribution of HLA-G in normal tissues appears broader than originally described. HLA-G expression was found in embryonic tissues, in adult immune privileged organs, and in cells of the hematopoietic lineage. More interestingly, under pathophysiological conditions HLA-G antigens may be expressed on various types of malignant cells suggesting that HLA-G antigen expression is one strategy used by tumor cells to escape immune surveillance. In this article, we will focus on HLA-G expression in cancers of distinct histology and its association with the clinical course of diseases, on the underlying molecular mechanisms of impaired HLA-G expression, on the immune tolerant function of HLA-G in tumors, and on the use of membrane-bound and soluble HLA-G as a diagnostic or prognostic biomarker to identify tumors and to monitor disease stage, as well as on the use of HLA-G as a novel therapeutic target in cancer.     

The FAT10- and ubiquitin-dependent degradation machineries exhibit common and distinct requirements for MHC class I antigen presentation

Like ubiquitin (Ub), the ubiquitin-like protein FAT10 can serve as a signal for proteasome-dependent protein degradation. Here, we investigated the contribution of FAT10 substrate modification to MHC class I antigen presentation. We show that N-terminal modification of the human cytomegalovirus-derived pp65 antigen to FAT10 facilitates direct presentation and dendritic cell-mediated cross-presentation of the HLA-A2 restricted pp65(495-503) epitope. Interestingly, our data indicate that the pp65 presentation initiated by either FAT10 or Ub partially relied on the 19S proteasome subunit Rpn10 (S5a). However, FAT10 distinguished itself from Ub in that it promoted a pp65 response which was not influenced by immunoproteasomes or PA28. Further divergence occurred at the level of Ub-binding proteins with NUB1 supporting the pp65 presentation arising from FAT10, while it exerted no effect on that initiated by Ub. Collectively, our data establish FAT10 modification as a distinct and alternative signal for facilitated MHC class I antigen presentation.     

Detection of human antigens on the surface of mouse cells transformed by chromosome transfer]

Mouse embryo cells, transformed in vitro by the transfer of chromosomes from HeLa human tumour cells, express a surface antigen (s) also found on HeLa cells. This antigen(s), which has been detected both by indirect immunofluoresence and by a 125I-protein A binding assay, is not an antigen(s) shared by both Human and Mouse cells.     

H-Y antigen expression in heterogametic males (XY) and females (ZW): a factor in reproductive strategy?

The cells of heterogametic females with ZW sex chromosomes express H-Y or H-W antigen. A hypothesis is formulated to explain why these animals are capable of 'practicing' amphigonia retardata, i.e., delay in actual fertilization of eggs by retaining viable sperm within the oviduct for a considerable time (several months).     

Evolutionary and functional perspectives of the major histocompatibility complex class I antigen-processing machinery

Major histocompatibility complex (MHC) class I molecules present antigenic peptides to CD8+ T cells, providing the basis for immune recognition of pathogen-infected cells. Peptides generated mainly by proteasomes in the cytosol are transported into the lumen of the endoplasmic reticulum by transporters associated with antigen processing (TAP). The maturation of MHC class I molecules is controlled by a number of accessory proteins and chaperones that are to a varying degree dedicated to the assembly of MHC class I. Several newly characterised proteins have been demonstrated to play important roles in this process. This review focuses on the functional relationship and evolutionary history of the antigen-processing machinery (APM) components and MHC class I itself. These are of great interest for further elucidating the origin of the immune system and understanding the mechanisms of antigen presentation and immunology in general.     

Evaluation of cellular immunity after rabies vaccination in man]

The peripheral lymphocytes of vaccinated men were stimulated by homologous antigen or its subunits (nucleocapsid and glycoprotein) or by some parent viruses (Mokola and Lagos). All subjects produced a high level of antibody. A difference was noted between the two types of immunity. A lack of cell-mediated immunity could explain the very few failures in Pasteur antirabies treatment.     

Inclusion of Gross virus cell surface associated antigen in liposomes]

The Gross virus associated cell surface antigen GCSAa was extracted from (C58NT)D cells by solubilization of membranes with detergent and partially purified. This antigen was entraped in liposomes. Absorption experiments of the cytotoxic activity towards EmaleG2 cells of a W/Fu anti (C58NT)D serum showed the presence of the antigen at the surface of sensibilized liposomes.     

New lectin receptors in carcinoembryonic antigen (CEA).

The glycoprotein CEA (carcinoembryonic antigen) carries carbohydrate groups, which react with the plant lectins from Agaricus bisporus, Arachis hypogaea (peanut), with Tridacnin from invertebrate clams and with the anti-A lectins from snails. Accordingly, it has cryptantigenic structures, which correspond to the T or T-like antigen, the Tridacnin receptor and to the so called A-like antigen.