Interleukin-18: biological properties and clinical implications

IL-18, originally identified as interferon-gamma inducing factor (IGIF), is related to the IL-1 family in terms of its structure, processing, receptor, signal transduction pathway and pro-inflammatory properties. IL-18 is also functionally related to IL-12, as it induces the production of Th1 cytokines and participates in cell-mediated immune cytotoxicity. This review summarizes the recent advances in the understanding of IL-18 structure, processing, receptor expression and immunoregulatory functions, and focuses on the role of IL-18 modulation in tumours, infections, and autoimmune and inflammatory diseases.

Structural basis of the interaction between IgG and Fcgamma receptors

The binding of multivalent antigen-antibody complexes to receptors for the Fc portion of IgG (FcgammaR) induces the clustering of the FcgammaR and triggers cell activation leading to defence reactions against pathogens. The Fc portion of IgG consists of two identical polypeptide chains which are related to each other by a 2-fold axis and are folded in two structural domains, the C(H)2 domain, near the flexible hinge region of the IgG molecule, and the C(H)3 domain. We studied the interaction in solution between the Fc fragment of mouse IgG2b and the extracellular region of mouse FcgammaRII. We find that one Fc molecule binds one FcgammaRII molecule only. Using NMR spectroscopy, we show that FcgammaRII binds to a negatively charged area of the C(H)2 domain, corresponding to the lower hinge region, and that the binding of FcgammaRII onto one of the two symmetrically related sites on the Fc induces a conformational change in the other site. We therefore propose a model that explains why IgG molecules are unable to trigger FcgammaR-mediated cellular responses spontaneously in the absence of crosslinking by multivalent antigens.

Cytokines and soluble cytokine receptor induction after IL-12 administration in cancer patients

This study shows that subcutaneous administration of increasing doses of IL-12, once a week, in 21 cancer patients increased the expression of cytokine genes (interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), IP-10, MIG, IL-10, IL-4) in peripheral blood mononuclear cells even at very low doses (30 ng/kg). Surprisingly, no circulating TNF-alpha or IL-4 could be detected in the plasma of patients treated with IL-12. However, a marked increase of soluble IL-4 receptor was demonstrated in the plasma of five of the six patients studied, which may represent an additional mechanism by which IL-12 inhibits the development of the Th2 response in vivo. A marked decline of IFN-gamma and IP10 induction was recorded after repeated cycles of IL-12. In contrast, in most patients IL-12 increased IL-10 expression with no subsequent decrease during the course of therapy, and even an earlier peak of IL-10 induction at the 6th cycle. In addition, a constant up-regulation of serum soluble IFN-gamma receptor levels was observed after each cycle of IL-12 treatment with a delayed peak compared with the IFN-gamma peak. The constant rise of IL-10 and soluble IFN-gamma receptor during IL-12 therapy may therefore contribute to the inhibition of IFN-gamma activity detected after repeated cycles of IL-12. Lastly, a marked heterogeneity of cytokine induction was observed from one patient to another, which appeared to be independent of the dose of IL-12 administered. These data may lead to a better understanding of the biological activity of IL-12 and the in vivo mechanisms of its regulation.

Ras and p53 intracellular targeting with recombinant single-chain Fv (scFv) fragments: a novel approach for cancer therapy?

Intracellular expression of recombinant antibodies allows one to interfere with the functions of oncogenic molecules expressed in various cell compartments and has therefore a vast clinical potential in cancer therapy. We inhibited the functions of oncogenic Ras mutant forms by intracellular expression of a neutralizing single-chain antibody (scFv). In vitro studies indicated that the scFv is expressed in the cytosol of Xenopus laevis oocytes and of tumor cells, blocks ras-mediated activation processes, and induces tumor cell death. In vivo studies performed using scFv cDNA inserted into an adenoviral vector showed that the scFv dramatically affects tumor growth. Second, intracellular expression of scFvs directed against p53 indicated that these antibody fragments can be successfully targeted to cell nucleus, bind p53, and partially restore the transcriptional activity of p53 mutants in human tumor cells. Thus, intracellular scFvs directed against oncogenic molecules may represent a new class of antitumor agents.

Signal regulatory proteins negatively regulate immunoreceptor-dependent cell activation

Signal regulatory proteins of the alpha subtype (SIRPalpha) are ubiquitous molecules of the immunoglobulin superfamily that negatively regulate protein tyrosine kinase receptor-dependent cell proliferation. Their intracytoplasmic domain contains four motifs that resemble immunoreceptor tyrosine-based inhibition motifs (ITIMs) and that, when tyrosyl-phosphorylated, recruit cytoplasmic SH2 domain-bearing protein tyrosine phosphatases (SHPs). ITIMs are borne by molecules that negatively regulate cell activation induced by receptors bearing immunoreceptor tyrosine-based activation motifs (ITAMs). Because SIRPalpha are coexpressed with ITAM-bearing receptors in hematopoietic cells, we investigated whether SIRPalpha could negatively regulate ITAM-dependent cell activation. We found SIRPalpha transcripts in human mast cells, and we show that a chimeric molecule having the transmembrane and intracytoplasmic domains of SIRPalpha could inhibit IgE-induced mediator secretion and cytokine synthesis by mast cells. Inhibition required that the SIRPalpha chimera was coaggregated with ITAM-bearing high affinity IgE receptors (FcepsilonRI). It was correlated with the tyrosyl phosphorylation of the SIRPalpha chimera and the recruitment of SHP-1 and SHP-2. The phosphorylation of FcepsilonRI ITAMs was decreased; the mobilization of intracellular Ca(2+) and the influx of extracellular Ca(2+) were reduced, and the activation of the mitogen-activated protein kinases Erk1 and Erk2 was abolished. SIRPalpha can therefore negatively regulate not only receptor tyrosine kinase-dependent cell proliferation but also ITAM-dependent cell activation.

Interleukin 17, a T-cell-derived cytokine, promotes tumorigenicity of human cervical tumors in nude mice

Interleukin (IL) 17 is a proinflammatory cytokine secreted mainly by activated human memory CD4 T cells that induces IL-6, IL-8, and nitric oxide. Because IL-6 and IL-8 have been implicated in the pathogenesis of cervical cancer, we investigated the action of IL-17 on human cervical tumor cell lines in vitro and in vivo. We showed that in vitro, IL-17 increases IL-6 and IL-8 secretion by cervical carcinoma cell lines at both protein and mRNA levels. No direct effect of IL-17 on in vitro proliferation of cervical tumor cell lines could be demonstrated. However, two cervical cell lines transfected with a cDNA encoding IL-17 exhibited a significant increase in tumor size as compared to the parent tumor when transplanted in nude mice. This enhanced tumor growth elicited by IL-17 was associated with increased expression of IL-6 and macrophage recruitment at the tumor site. A potential role of IL-17 in modulation of the human cervical tumor phenotype was also supported by its expression on the cervical tumor in patients with CD4 infiltration. IL-17 therefore behaves like a T-cell-specific cytokine with paradoxical tumor-promoting activity. This may partially explain previous reports concerning the deleterious effect of CD4 T cells in cancer.

Development of a direct in situ RT-PCR method using labeled primers to detect cytokine mRNA inside cells

We have developed an original protocol of direct in situ RT-PCR with biotinylated labeled primers to detect cytokine mRNA inside cells. This label improved the specificity of the technique compared with the use of digoxigenin or fluorescein-labeled primers. We found a reliable correlation between the known expression of cytokine mRNA in a given cell and a positive signal with in situ RT-PCR. Nuclear counterstaining demonstrated that the positive signal obtained was distributed in the cytoplasm in accordance with mRNA localization. In addition, direct demonstration of the presence of the expected PCR product in cell extracts without non-specific parasitic DNA amplification provided strong support for the specificity of the method. Designing the primers in order to prevent DNA amplification, the use of recombinant Thermus thermophilus (rTth) DNA polymerase and a decreased duration of each cycle of PCR by combining the annealing and hybridization steps improved the reproducibility and reliability of the technique and morphological preservation of the cells. Experiments in which different proportions of cytokine mRNA positive and negative cells were mixed argue against significant diffusion of PCR product into initially cytokine mRNA negative cells, thereby leading to false-positive results. In comparison with the direct incorporation of labeled dNTP during amplification, our procedure appears to ensure greater specificity and does not need DNAse treatment which is often difficult to standardize. Detection of IL-2 and IFNgamma mRNA induction after T cell activation using this direct in situ RT-PCR method showed that the technique may be helpful for monitoring cytokine gene expression at a single cell level.

Modulation of interleukin-18 expression in human colon carcinoma: consequences for tumor immune surveillance

The production in colon cancer of interferon-gamma (IFN-gamma), a type-1 T-helper (TH1) cytokine, is considered as a marker of good prognosis. We asked whether interleukin-18 (IL-18), which strongly induces IFN-gamma and regulates Fas ligand (Fas-L)-dependent cytotoxicity, may play a role in colon homeostasis, and if its expression was modulated in colon adenocarcinomas. We analyzed 14 specimens of colon adenocarcinomas, 6 of normal colon mucosa of the series, and 6 colon-tumor cell lines. The expression of IL-18, of ICE protease, involved in the processing of this cytokine, and of the downstream effectors of IL-18, IFN-gamma and Fas-L was analyzed by RT-PCR. We further performed IL-18 immunostaining of normal and tumor specimens. The results were correlated with tumor dissemination and clinical outcome. We report the synthesis of IL-18 in human normal colon, mainly by epithelial cells of the mucosa. Out of the 6 tumor cell lines, 4 expressed IL-18 transcripts, but neither ICE mRNA nor secreted forms of IL-18 were detected. We observed decreased or abolished synthesis of IL-18 in colon adenocarcinomas, as compared with normal mucosa. Thus, half of the colon-cancer tissues (7/14 cases) expressed neither IFN-gamma nor Fas-L. This feature was correlated with the existence of distant metastases (Fischer's exact test, p = 0.02) and an unfavorable outcome. These findings suggest that production of IL-18 in human colon may play a role in homeostasis and in tumor immune surveillance, by enhancing IFN-gamma production and Fas-L-dependent cytotoxicity of immune cells.

Modulation of interleukin-18 expression in human colon carcinoma: consequences for tumor immune surveillance

The production in colon cancer of interferon-gamma (IFN-gamma), a type-1 T-helper (TH1) cytokine, is considered as a marker of good prognosis. We asked whether interleukin-18 (IL-18), which strongly induces IFN-gamma and regulates Fas ligand (Fas-L)-dependent cytotoxicity, may play a role in colon homeostasis, and if its expression was modulated in colon adenocarcinomas. We analyzed 14 specimens of colon adenocarcinomas, 6 of normal colon mucosa of the series, and 6 colon-tumor cell lines. The expression of IL-18, of ICE protease, involved in the processing of this cytokine, and of the downstream effectors of IL-18, IFN-gamma and Fas-L was analyzed by RT-PCR. We further performed IL-18 immunostaining of normal and tumor specimens. The results were correlated with tumor dissemination and clinical outcome. We report the synthesis of IL-18 in human normal colon, mainly by epithelial cells of the mucosa. Out of the 6 tumor cell lines, 4 expressed IL-18 transcripts, but neither ICE mRNA nor secreted forms of IL-18 were detected. We observed decreased or abolished synthesis of IL-18 in colon adenocarcinomas, as compared with normal mucosa. Thus, half of the colon-cancer tissues (7/14 cases) expressed neither IFN-gamma nor Fas-L. This feature was correlated with the existence of distant metastases (Fischer's exact test, p = 0.02) and an unfavorable outcome. These findings suggest that production of IL-18 in human colon may play a role in homeostasis and in tumor immune surveillance, by enhancing IFN-gamma production and Fas-L-dependent cytotoxicity of immune cells.

Vav and SLP-76 recruitment by cross-linking of FcgammaRIIa1 in promyelocytic HL-60 cells

The signaling events induced upon cross-linking of the human FcgammaRIIa1 (CD32) which contains an immune receptor tyrosine-based activation motif (ITAM) in its intracellular region, were investigated in the promyelocytic HL-60 cells. It is shown here that the FcgammaRIIa1 engagement recruits the Ras pathway in these cells, as evidenced by the tyrosine-phosphorylation of the Shc adaptator protein and of the extracellular signal-regulated kinase 2 (ERK2). However, p95vav, a molecule able to interact with Rac-1 and to regulate cytoskeletal reorganization, was also found to be phosphorylated. In addition, co-immunoprecipitation experiments demonstrated that Vav is associated with SLP-76 upon FcgammaRIIa1 activation. A strong phosphorylation of p120cbl was also observed. The phosphorylation of molecules such as p95vav, SLP-76 and p120cbl suggests that FcgammaRIIa1 triggering also activates signaling pathways other than the Ras pathway.

Control of tumor development by intratumoral cytokines

The local immune reactions may influence the clinical outcome of human tumors. In carcinoma of the cervix, high gene expression of IL6 with tumor invasiveness whereas lack of gene expression of IFNbeta is correlated with poor prognosis. In colorectal cancer, lack of expression of IFNbeta is associated with the presence of distant metastasis and poor survival. The production of IL17 and IL18, inducers of IL6 and IFNbeta respectively is regulated in these tumors and may control the levels of the effector cytokines, i.e. IL6 and IFNbeta. The mechanisms by which these cytokines act are linked to the recruitment of effector cells such as macrophages.

Regulation of production of soluble Fc gamma receptors type III in normal and pathological conditions

CD16 (Fc gamma R type III), a low affinity IgG Fc receptor, is found in two forms, a transmembrane Fc gamma RIIIa expressed by NK cells and monocytes and a phosphatidylinositol-linked Fc gamma RIIIb present on neutrophils. Exposure of neutrophils to inflammatory signals induces a rapid loss of CD16 expression and release of a soluble form of CD16 (sCD16). Soluble CD16 circulates in plasma, levels being reduced in sera from patients with multiple myeloma. In the present manuscript the authors summarize work that aimed to better understand: (i) the role of proteinases in sCD16 production and CD16 membrane shedding; and (ii) the regulation of sCD16 levels in multiple myeloma patients and the possible biological consequences of its decrease in this disease. Soluble CD16 was purified from human serum. Its N-terminal sequencing demonstrated that it originates from neutrophil CD16 and its C-terminal sequencing showed that the cleavage site was between Val 196 and Ser 197, close to the membrane anchor. Analysis of the effect of protease inhibitors revealed that the cleavage leading to sCD16 production by PMA-activated neutrophils was metalloproteinase-dependent. In addition, membrane and sCD16 were sensitive to serine proteinases released by azurophil granules or added under purified form. The reduction of sCD16 levels that occurs in patients with multiple myeloma was associated with a slight decrease in circulating neutrophils, but not with a significant defect in sCD16 production by neutrophils, as detected in vitro. Moreover, addition of a recombinant sCD16 to plasmocytoma lines did not significantly modify their proliferation and Ig secretion.

Gene therapy study of cytokine-transfected xenogeneic cells (Vero-interleukin-2) in patients with metastatic solid tumors

On the basis of compelling preclinical data in cats and dogs, we initiated a clinical gene therapy study in nine patients with advanced solid tumors using xenogeneic fibroblasts secreting human interleukin (IL)-2 (Vero-IL-2 cells). Cohorts of three successive patients with tumors accessible to computed tomography- or ultrasound-guided injection were treated repeatedly with 5 x 10(5), 5 x 10(6), or 5 x 10(7) Vero-IL-2 cells. The endpoints of the study were feasibility, toxicity, and the clinical and biological effects of this novel approach to immunotherapy of cancer. Histopathological, immunological, and molecular analyses were performed on biopsy specimens of tumors and blood samples before, during, and after treatment. Treatment was well tolerated, and toxicity consisted of transient fever in one patient and short-lived, mild itching and erythema in two others. One patient with soft-tissue sarcoma showed a reduction of >90% and >50% of the volume of two distant, noninjected metastases, lasting for 29+ and 26 months, respectively. Four other patients showed stabilization of their disease for 3-9 months; of these patients, one with melanoma developed marked vitiligo. We conclude that repeated injections of < or =5 x 10(7) Vero-IL-2 cells are feasible and safe in heavily pretreated patients with advanced solid tumors. An additional evaluation of an intratumoral application of Vero-IL-2 seems warranted.

Negative regulation of c-kit-mediated cell proliferation by Fc gamma RIIB

Fc gamma RIIB are single-chain low-affinity receptors for IgG that bear an immunoreceptor tyrosine-based inhibition motif in their intracytoplasmic domain and that negatively regulate immunoreceptor tyrosine-based activation motif-dependent cell activation. They are widely expressed by cells of hematopoietic origin. We investigated here whether Fc gamma RIIB could also negatively regulate protein tyrosine kinase receptor (RTK)-dependent cell proliferation. As an experimental model, we used growth factor-dependent mast cells that constitutively express Fc gamma RIIB and c-kit, an RTK prototype. We found that anti-c-kit Abs mimicked the effect of stem cell factor and induced thymidine incorporation in Fc gamma RIIB-/-, but not in wild-type (wt) mast cells unless Fc gamma RIIB were blocked or anti-c-kit F(ab')2 were used. When coaggregated with c-kit by intact Abs in wt mast cells, Fc gamma RIIB inhibited thymidine incorporation, as well as cell proliferation, and inhibition was correlated with an arrest of cells in G1 during the cell cycle. The coaggregation of c-kit with Fc gamma RIIB did not affect ligand-induced c-kit phosphorylation and induced the tyrosyl-phosphorylation of Fc gamma RIIB, which selectively recruited the Src homology 2 domain-bearing inositol 5-phosphatase SHIP. Our results indicate that IgG Abs to growth factors or growth factor receptors may control RTK-dependent proliferation of a variety of cells that express Fc gamma RIIB.

Generation of phagocytic MAK and MAC-DC for therapeutic use: characterization and in vitro functional properties

Phagocytic cells with macrophage or dendritic cell phenotype, able to capture and ingest tumor cells, were derived in large numbers from peripheral blood mononuclear cells using two different activation procedures. Peripheral blood mononuclear cells were stimulated in nonadherent conditions in the presence of human AB serum with either granulocyte-macrophage colony-stimulating factor and dihydroxy-vitamin D3 for 7 days and with interferon-gamma for the last 18 hours to obtain activated macrophages (MAK) or with granulocyte-macrophage colony-stimulating factor and interleukin-13 for 7 days (with fresh interleukin-13 added on day 4) to obtain macrophage-dendritic cells (MAC-DC). A strong ability of MAC-DC to phagocytose yeasts was observed, in contrast to a low-intermediate phagocytosis capacity by MAK. Both CD14+ FCgammaR+ (FcgammaRI/CD64, FcgammaRII/CD32, FcgammaRIII/CD16) MAK and CD1a+/CD86+, CD14- MAC-DC were able to phagocytose whole tumor cells. However, only MAK phagocytosis was enhanced by FcgammaR engagement. MAK but not MAC-DC could lyse tumor cell in antibody-dependent cell cytotoxicity assays, via FcgammaRI. Thus, MAK as well as MAC-DC may represent valuable tools for different in vivo therapy strategies that do or do not include the use of monoclonal antibodies.

Differential roles of N- and C-terminal immunoreceptor tyrosine-based inhibition motifs during inhibition of cell activation by killer cell inhibitory receptors

Killer cell inhibitory receptors (KIRs) inhibit NK and T cell cytotoxicity when recognizing MHC class I molecules on target cells. They possess two tandem intracytoplasmic immunoreceptor tyrosine-based inhibition motifs (ITIMs) that, when phosphorylated, each bind to the two Src homology 2 domain-bearing protein tyrosine phosphatases SHP-1 and SHP-2 in vitro. Using chimeric receptors having an intact intracytoplasmic KIR domain bearing both ITIMs (N + C-KIR), a deleted domain containing the N-terminal ITIM only (N-KIR), or a deleted domain containing the C-terminal ITIM only (C-KIR), we examined the respective contributions of the two ITIMs in the inhibition of cell activation in two experimental models (a rat mast cell and a mouse B cell line) that have been widely used to analyze KIR functions. We found that the two KIR ITIMs play distinct roles. When coaggregated with immunoreceptor tyrosine-based activation motif-bearing receptors such as high-affinity IgE receptors or B cell receptors, the N + C-KIR and the N-KIR chimeras, but not the C-KIR chimera, inhibited mast cell and B cell activation, became tyrosyl-phosphorylated, and recruited phosphatases in vivo. The N + C-KIR chimera recruited SHP-1 as expected, but also SHP-2. Surprisingly, the N-KIR chimera failed to recruit SHP-1; however, it did recruit SHP-2. Consequently, the N-terminal ITIM is sufficient to recruit SHP-2 and to inhibit cell activation, whereas the N-terminal and the C-terminal ITIMs are both necessary to recruit SHP-1. The two KIR ITIMs, therefore, are neither mandatory for inhibition nor redundant. Rather than simply amplifying inhibitory signals, they differentially contribute to the recruitment of distinct phosphatases that may cooperate to inhibit cell activation.

Gene therapy with cytokine-transfected xenogeneic cells in metastatic tumors

On the basis of compelling preclinical data in cats and dogs we initiated a clinical gene therapy study in nine patients with advanced solid tumors using xenogeneic fibroblasts secreting human IL-2 (Vero-IL-2 cells). Cohorts of three successive patients with tumors accessible to CT- or ultrasound-guided injection were treated repeatedly with 5 x 10(5), 5 x 10(6), or 5 x 10(7) Vero-IL-2 cells. Endpoints of the study were feasibility, toxicity, and clinical and biological effects of this novel approach to immunotherapy of cancer. Histopathological, immunological and molecular analyses were performed on biopsy specimens of tumors and blood samples from before, during and after treatment. Low levels of serum antibodies to Vero cells developed in 2/9 patients. Analysis of tumor biopsies showed increased expression of CD3 mRNA and enhanced tumor infiltration with varying lymphocyte subpopulations after treatment. In addition, monoclonal alterations of the TCR repertoire of blood and tumor lymphocytes were observed. Treatment was well tolerated and toxicity consisted of transient fever in one patient and short-lived, mild itching and erythema in two others. One patient with soft tissue sarcoma showed a more than 90% and more than 50% reduction of the volume of two distant, non-injected metastases, respectively, lasting for 22+ months. Four other patients showed stabilization of their disease for three to nine months, among whom was a patient with melanoma who developed marked vitiligo. We conclude that repeated injection of up to 5 x 10(7) Vero-IL-2 cells was safe and showed biological and clinical activity in heavily pretreated patients with advanced solid tumors. Further evaluation of intratumoral application of Vero-IL-2 seems warranted.

Immunoglobulin variable regions usage by B-lymphocytes infiltrating a human breast medullary carcinoma

Breast medullary carcinoma are heavily infiltrated by B-lymphocytes and associated with a good prognosis despite their high histological grade. We investigated the Ig repertoire of B-lymphocytes infiltrating one such tumour. A single cell suspension was obtained from a tumor specimen by enzymatic digestion. VH, Vkappa, and Vlambda regions were amplified by RT-PCR using mixtures of primers optimized to maximize the diversity of the PCR products. They were then cloned and sequenced. Analysis of 9 VH, 5 Vkappa, and 10 Vlambda sequences using the Kabat database indicated that several VH and VL region subgroups (I, II and III) are expressed by B-lymphocytes infiltrating this tumor. The analysis of CDR3 regions also showed a variability, although some VH and VL clones exhibited identical or nearly identical sequences. Thus, the B-cell infiltration observed in this breast medullary carcinoma does not reflect a monoclonal proliferation and represents an oligoclonal or a polyclonal B-cell proliferation.

Soluble CD16 in plasma cell dyscrasias

Soluble forms of Fc gammaR type III (sFc gammaRIII or sCD16) are present in many biological fluids. Their main ligand is IgG in the form of complexes. In plasma, sCD16 essentially derive from cleavage of membrane CD16 (or Fc gammaRIII) present on neutrophils and, to a lesser extent, on NK cells. Determination of sCD16 serum level during monoclonal gammopathies has demonstrated markedly reduced levels in multiple myeloma and in monoclonal gammopathy of undetermined significance (MGUS) rapidly evolving to multiple myeloma, compared to stable MGUS or controls, indicating a prognostic value for this biological parameter. The biology and functions of sCD16 are described, together with the biological significance of modifications of the sCD16 serum level in monoclonal gammopathies.

Structurally different anthracyclines provoke different effects on cell cycle and tumor B cell differentiation

Previously we have detected a stimulatory effect on immunoglobulin (IgG) synthesis when hybridoma cells were treated with doxorubicin. In order to determine whether this is a general property of anthracycline, we have selected three analogs--doxorubicin (DOX), pirarubicin (THP-DOX) and aclarubicin (ACR)--which differ mainly in the methylation state of their amino sugars. Cell cycle analysis by flow cytometry and drug localization by scanning confocal microscopy were also performed. The results show that when cells (UN2 hybridoma B cells), were exposed to subtoxic doses of DOX or THP (with unmethylated amino sugars), a strong increases in IgG secretion, heavy (H) and light (L) chain synthesis and the corresponding mRNA levels were induced. Furthermore these two drugs arrested the cells in the G2/M phase of the cell cycle. In contrast, exposure to ACR (with its methylated amino sugar) at similar subtoxic doses induced a blockade of cells in the G1 phase with no increase of IgG synthesis, at the subtoxic doses used, all three drugs could still be detected in the nucleus as well as in the cytoplasm, as determined by confocal laser microscopy. Thus, the relationship between cell cycle blockade, IgG stimulation and anthracycline structure is suggested by these results.

Major histocompatibility complex class I presentation of exogenous soluble tumor antigen fused to the B-fragment of Shiga toxin

Targeting exogenous antigen into the MHC class I-restricted presentation pathway is a prerequisite for the induction of cytotoxic T lymphocytes (CTL) which have been shown to represent an important component of the protective and therapeutic immune response to viral infections and tumors. In this study, we produced recombinant proteins composed of the receptor-binding non-toxic B-fragment of bacterial Shiga toxin derived from Shigella dysenteriae associated with an epitope from a model tumor antigen, Mage 1. We show that Shiga B-Mage 1 fusion proteins carrying an active or inactive endoplasmic reticulum retrieval signal (the C-terminal peptides KDEL or KDELGL, respectively) could be presented by peripheral blood mononuclear cells in an MHC class I-restricted manner to Mage 1-specific CTL. After pulsing B lymphoblastoid cells or dendritic cells with Shiga B-Mage 1 fusion protein, activation of the MHC class I-restricted Mage 1-specific CTL was also demonstrated. In further analysis, we showed that treatment with brefeldin A or paraformaldehyde fixation of Epstein-Barr virus-transformed B cells prevented the presentation of the Mage 1 T cell epitope, which excluded extracellular processing of the antigen. Immunofluorescence analysis also revealed that the Shiga B-Mage 1 fusion protein was largely excluded from Lamp-2-positive lysosomal structures. Therefore, the ability of Shiga toxin B-fragment to target dendritic cells and B cells and to direct antigen into the exogenous class I-restricted pathway makes it an attractive non-living and non-toxic vaccine vector.

Fc receptors as targets for immunotherapy

Human membrane and soluble Fc epsilon receptors (Fc epsilon RI, Fc epsilon RII/CD23) and Fc gamma receptors (Fc gamma RI/CD64, Fc gamma RII/CD32, Fc gamma RIII/CD16) have been implicated in a number of diseases. Their functional roles such as capture and clearance of immune complexes, antibody-dependent cell cytotoxicity, or cytokine or inflammatory mediator release, make them potential targets for immuno-intervention. In the present review, we will describe how membrane and soluble human Fc epsilon R and Fc gamma R have been already used as targets/tools for immuno-interventions by using monoclonal and bispecific engineered antibodies. Some therapeutic uses of these molecules both in cancer, infectious, and auto-immune diseases are presented.