Search

Interleukin 9 (IL-9) is a T-cell-derived lymphokine that induces the proliferation of various lymphoid and hemopoietic cells. A cDNA clone encoding the murine IL-9 receptor was isolated by expression cloning in COS cells and screening with 125I-labeled IL-9. Transient expression of this cDNA produced high-affinity binding sites for IL-9. The predicted 52-kDa protein contains a putative signal peptide and a typical transmembrane domain. A cDNA for the human homologue was isolated by cross-hybridization. Transfection of this cDNA in a murine T-cell clone conferred responsiveness to human IL-9. Sequence analysis revealed that the IL-9 receptor belongs to the recently described hematopoietin receptor super-family and is expressed in membrane-bound and soluble forms.

Interleukin-P (IL-9) is a T cell-derived cytokine that induces the proliferation of various lymphoid and hematopoietic cells. Recombinant murine IL-9 expressed in a baculovirus system allowed us to demonstrate the existence of saturable and specific binding sites for IL-9. Scatchard analysis was consistent with the existence of a single class of receptors with a Kd of ∼ 100 pM. Cross-linking studies indicated that the IL-9 receptor consisted of a 64 kD glycoprotein, the molecular weight of which was reduced to 54 kD after deglycosylation. Specific binding sites for murine IL-9 were detected on T helper clones, on several T cell tumors, on macrophages and on mast cell lines. A cDNA encoding the murine IL-9 receptor was isolated by expression cloning. Affinity constant and molecular weight of the protein encoded by this cDNA are similar to those described for the native receptor. Sequence analysis indicated that the IL-9 receptor belongs to the hematopoietin receptor family, L’interleukine-9 (IL-9) est une cytokine sécrétée par certains clones de lymphocytes T auxiliaires et qui stimule la prolifération de diverses cellules lymphoïdes et hématopoiétiques. A l’aide de la protéine recombinante exprimée dans le système du baculovirus, nous avons démontré l’existence de récepteurs spécifiques et saturables pour l’IL-9 murine. A l’équilibre, nous avons détecté la présence d’une seule classe de récepteurs caractérisés par une constante d’affinité de ~10pM. Par couplage covalent de l’IL-9 à son récepteur, la taille de la chaîne qui fixe l’IL-9 a été évaluée à 64 kD, celle-ci étant réduite à 54 kD après déglycosylation. Des sites de fixation spécifiques de l’IL-9 murine ont été détectés sur des clones de lymphocytes T auxiliaires, sur plusieurs lignées tumorales d’origine T, sur des macrophages ainsi que sur des lignées mastocytaires. Un cDNA codant pour le récepteur de l’IL-9 murine a été isolé par une méthode de clonage par expression. L’analyse de la séquence révèle la présence des séquences consensus des récepteurs de la famille des facteurs hématopoiétiques. La constante d’affinité et la taille du récepteur cloné sont semblables à celles mesurées pour le récepteur naturel, Thèse de doctorat en sciences pharmaceutiques -- UCL, 1992

To test the transforming potential of deregulated P40/Interleukin 9 expression, we transfected a mouse P40-dependent T cell line with P40 cDNA, and examined the tumorigenicity of the resulting transfectants. When the cells, which grew autonomously in vitro, were injected intraperitoneally or subcutaneously into syngeneic mice, a very high tumor incidence was observed with as few as 10(4) cells per inoculum. Animals died as a result of widespread dissemination of lymphomatous tissue to abdominal and thoracic organs. The same P40-dependent cell line transfected with a control construct did not form tumors even after injection of 10(7) cells. These results indicate that uncontrolled expression of P40 can support T cell proliferation in vivo, and may be a transforming event involved in the development of certain T cell tumors.

The existence of saturable and specific binding sites for mouse P40/IL-9 was demonstrated on a variety of factor-dependent T cell lines derived from Th clones by long term culture in the presence of P40-containing T cell supernatants. Scatchard transformation of the data obtained with one such line was consistent with the existence of a single class of receptors with a Kd of approximately 100 pM and a density of 3000/cell. P40 binding to these cells was followed by rapid internalization of the ligand. P40-receptors (P40-R)3 were also found on certain Th clones maintained in conventional cultures, especially after stimulation with Ag and APC. Only T cell clones that proliferated in response to P40 showed significant levels of binding, suggesting that the regulation of P40-R expression is an important element in the control of P40-responsiveness. In accord with this idea, fresh T cells, cytolytic T cell clones and a wide variety of other cells including B cells and fibroblasts, which do not proliferate in response to P40, showed no significant binding. However, P40-R were not restricted to a few unusual Th clones. They were also detected on several T cell tumors, on macrophages and on mast cell lines. The latter point is of particular interest in view of the mast cell growth factor activity recently ascribed to P40. Cross-linking studies with T-cell lines and mast cells indicated that the P40-R consists of a 64-kDa glycoprotein, the molecular mass of which is reduced to 54 kDa on treatment with N-glycosidase F.

To better understand the role of free radicals in liver carcinogenesis, endogenous antioxidant defense systems and the susceptibility of membranes to lipid peroxidation were evaluated in early lesions and in malignant tumors induced by the Solt-Farber resistant hepatocyte protocol. These parameters were also measured in the liver surrounding these tumors. In comparison with the normal liver, both nodules and carcinomas show a different biochemical pattern consisting of decreased glutathione peroxidase (GSH peroxidase) and catalase activities plus increased glutathione reductase (GSSG reductase) activity. In contrast, 1 week after the application of the initiation-selection protocol, the liver displays a high level of glutathione (GSH), high GSSG reductase activity, a reduced production of malondialdehyde and no changes in superoxide dismutase and GSH peroxidase activities. These data suggest that the liver is well protected against reactive oxygen species. During the carcinogenic process, the liver parenchyma surrounding the altered foci recovers from most of the modifications induced by the initiation-selection treatment. These results add additional support for the hypothesis that the appearance of early alterations in the liver, after a carcinogenic treatment, might be an adaptive response to a hazardous environment in which selected cell populations are transformed into nodules and/or carcinomas.