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Biomedical subjects

B Ryffel

Publications and source records attributed to B Ryffel.

At least 91 records · Page 5Linked to original sources
PubMed1994

Interleukin-6 exacerbates glomerulonephritis in (NZB x NZW)F1 mice.

The ability of interleukin-6 (IL-6) to modulate immune parameters and mesangial cell function suggests a role for this cytokine in the development of autoimmune glomerulonephritis. This hypothesis was tested in 6-month-old female (NZB x NZW)F1 mice that were administered recombinant human IL-6 (rhIL-6) (50 and 250 micrograms/kg s.c.) for 12 weeks, resulting in an accelerated and severe form of membranoproliferative glomerulonephritis associated with marked upregulation of mesangial major histocompatibility complex class II antigen and glomerular ICAM-1 expression. To distinguish direct effects of rhIL-6 on the renal mesangium from those mediated through the immune system, (NZB x NZW)F1 mice were immunosuppressed with cyclosporin. Immunosuppression by cyclosporin inhibited the development of glomerulonephritis, decreased class II antigen expression, and abrogated IL-6-mediated effects. Administration of neutralizing anti-IL-6 antibody had no effect on the spontaneous development of glomerulonephritis in (NZB x NZW)F1 mice. This finding, together with undetectable IL-6 serum levels, makes a pathogenetic role of endogenously produced IL-6 in this disease model unlikely. In contrast to (NZB x NZW)F1 mice, parental NZW or BALB/c mice given high doses of rhIL-6 (500 micrograms/kg) or recombinant murine IL-6 (100 micrograms/kg) daily for 4 weeks failed to develop morphological or biochemical evidence of glomerulonephritis. Induction of acute phase proteins, anemia, thrombocytosis, and induction of renal class II antigen confirmed the biological activity of IL-6 in these mice. In conclusion, while non-nephritogenic in normal mice, IL-6 accelerates the development of the genetically determined glomerulonephritis of (NZB x NZW)F1 mice through effects mediated by a modulated immune system. Since neutralizing IL-6 antibody treatment did not prevent the development of glomerulonephritis, it is unlikely that increased IL-6 production plays a role in the pathogenesis of lupus nephritis.

Animals↗
PubMed1993

Binding of active cyclosporins to cyclophilin A and B, complex formation with calcineurin A.

The binding properties of several active and inactive cyclosporins to the major intracellular receptor proteins, cyclophilin A and B, as well as the interaction with the phosphatase calcineurin were investigated by ELISA and by means of a photoaffinity labeled probe (PL-CS). Binding to recombinant human cyclophilin A and B was rapid and saturable, and correlated with the in vitro immunosuppressive activity of cyclosporin derivatives. In the presence of cyclophilin A or B and calcium cyclosporin binds specifically to purified bovine calcineurin. PL-CS labeled only the calcineurin A subunit, but not the B subunit or calmodulin. Calcineurin A binding was competed by active (CsA, CsG or CsM), but not inactive (CsH, CsF) derivatives or the structurally unrelated macrolide immunosuppressant FK506. Ternary complexes containing equimolar ratios of cyclophilin A or B, PL-CS and calcineurin were resolved by chemical-crosslinking. The formation of these complexes was apparently specific, calcium-, but not calmodulin-dependent, and only inhibited by active cyclosporins. In vivo labelling of Jurkat T-cells revealed, that cyclophilin A and calcineurin A are the main labeled proteins, which form complexes in the presence of active cyclosporin. Thus, we demonstrate directly, that active cyclosporins have two recognition sites, which allow the in vivo recognition of cyclophilins and calcineurin A.

Affinity Labels↗
PubMed1993

Inhibition of activation-induced changes in the structure of the T cell interleukin-7 receptor by cyclosporin A and FK506.

We have recently shown that activation of T cells causes structural changes in the interleukin-7 receptor (IL-7R) (Foxwell et al. Int. Immunol. 1992, 4: 277). Unactivated cells expressed a receptor characterized as a cross-linked protein of 107-kDa whereas activated cells had reduced levels of this 107-kDa complex and now express a major cross-linked product of 93 kDa. These changes in receptor expression were concomitant with the acquisition of IL-7 growth responsiveness by activated T cells. In this study, the effect of the potent immunosuppressive agents cyclosporin A and FK506 on the activation-induced responsiveness to IL-7-driven proliferation and the concomitant changes in receptor structure have been investigated. Cyclosporin A and FK506 suppressed the expression of the 93-kDa complex and the loss of the 107-kDa complex on activated cells. The presence of exogenous IL-7 inhibited the effects of the drugs on IL-7R structure, allowing expression of the 93-kDa complex. Expression of the 93-kDa complex could also be induced either by ionomycin or phorbol esters. As observed for other T cell activation parameters, only those which induced a calcium signal (ionomycin) but not protein kinase C (phorbol esters) were sensitive to the drugs. In all studies, the expression of the 93-kDa complex correlated with the ability of cells to proliferate to IL-7, and thus these results further support the hypothesis that the 93-kDa form of the IL-7R is required to transmit the cytokine's growth signal. Moreover, these data suggest that activation-induced transcriptional events are required for the expression of the 93-kDa complex and the down-regulation of the 107-kDa complex. As reported for IL-2R and IL-4R, our data also show that the expression of another T cell growth factor receptor is sensitive to the effects of cyclosporin A and FK506. These observations also have important implications for reported cyclosporin A effects on the thymus where IL-7 can act as a growth factor for thymocytes.

Cells, Cultured↗
PubMed1993

Cross-linking of human neutrophil surface proteins to iodinated interleukin 8 or neutrophil activating peptide-2 results in at least four separable proteins.

The human neutrophil activating peptides-1 and -2 (NAP-1/IL-8, NAP-2) are two structurally and functionally related members of the chemokine cytokine family. They are chemoattractants and activators of neutrophils and exert their effects by binding to specific receptors which are expressed on responsive cells. Two closely related IL-8 receptors of neutrophils have been characterized recently by molecular cloning. We show here that NAP-1/IL-8 and NAP-2 can be cross-linked to at least four protein bands from human neutrophil surfaces with apparent molecular masses of 55, 65, 71 and 81 kDa. The two cross-linked proteins with lower masses were associated with high, the two with the higher masses with low affinity binding of NAP-2, NAP-1/IL-8 was bound to all bands with high affinity. NAP-1/IL-8 and NAP-2 could also be cross-linked to form dimers when bound to cells and in solution. Our results show that more than two NAP-1/IL-8 receptors, or more than two forms of the known receptors exist. Alternatively, the four protein bands can be explained by cross-linking of ligand monomers and dimers, respectively, to the known receptors of neutrophils.

Cross-Linking Reagents↗
PubMed1993

Pathology induced by leukemia inhibitory factor.

Leukemia inhibitory factor is a glycoprotein growth and differentiation factor with pleiotropic activity. LIF has potent effects on the hematopoietic system, including megakaryocyte progenitor cells. In addition, LIF has bone regeneration activity, induces cachexia and acute-phase response in hepatocytes, and inhibits adipogenesis, to mention the more important activities. In vivo LIF treatment in monkeys and rodents was followed by signs of general toxicity, cachexia, acute-phase reaction, and stimulation of hematopoiesis. The safety margin for possible therapeutic effects on hematopoiesis seems to be very narrow.

Acute-Phase Reaction↗
PubMed1993

TNF receptor distribution in human tissues.

The nature and location of cells responding to tumor necrosis factor-alpha were investigated in situ by immunohistochemistry using monoclonal antibodies directed against the p75 and p55 proteins of the TNF receptor. Receptor expression was found in the thymus and secondary lymphoid tissues. In the thymus, the p75 receptor was confined to medullary lymphoblasts and dendritic cells, which costain with the Tac protein of the interleukin-2 receptor. In lymph nodes and other secondary lymphoid tissues, the p75 receptor was expressed on activated lymphocytes and interdigitating reticulum cells of the T cell areas, whereas the p55 receptor was confined to the germinal center dendritic reticulum cells, which are the main site of TNF-alpha production. TNF receptor proteins were up-regulated in reactive hyperplasia together with increased TNF-alpha expression. Surprisingly, no TNF-R was detectable on nonlymphoid tissues. The species specificity of these TNF-antibodies was high: whereas the antibodies cross-reacted with epitopes in nonhuman primates, no immunoreactivity was detected in lower animal species, e.g., dog, rabbit, and rodents. The data presented suggest that TNF-alpha, which is produced by germinal center DRCs, might regulate an in vivo immune response through autocrine and paracrine pathways, e.g., through the p55 and p75 receptor proteins, which are expressed at different sites on the lymphoid tissue.

Antibodies, Monoclonal↗
PubMed1993

Evidence for shared receptor proteins for human interleukin-3 and granulocyte-macrophage colony-stimulating factor in the human M-07 cell line.

The biologic response of the human leukemia cell line M-07 to granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin 3 (IL-3) and interleukin 4 (IL-4) is mediated by a low number of high affinity receptors. Cross-competition studies revealed that IL-3 and GM-CSF partially inhibited the specific binding of the heterologous radiolabeled ligand, whereas IL-4 binding was not affected by these cytokines. The molecular mechanism of cross-competition was investigated by chemical crosslinking and immunoprecipitation. Trimolecular receptor complexes consisting of a major 73kDa and two minor 120 and 128kDa membrane proteins for IL-3, and a major 84kDa and two minor 120 and 130 kDa proteins for GM-CSF were found on M-07 cells. The 73 and 84kDa proteins represent distinct and non-linked membrane proteins and are identical with the cloned, low affinity IL-3 and GM-CSF receptor proteins (Gearing et al, 1989, Hayashida et al, 1990). The higher molecular weight proteins share common binding sites as evidenced by immunoprecipitation of double-crosslinked membranes. The 120/128kDa proteins are most likely identical with the recently cloned and shared beta-subunit of the IL-3 and GM-CSF receptor (Kitamura et al, 1991) containing a single or two IL-3 and/or GM-CSF molecules.

Binding, Competitive↗
PubMed1993

Pathology induced by interleukin-6.

Interleukin-6 (IL-6) is a multifunctional cytokine that plays an important role in the immune response, hemopoiesis, and host defense. Recombinant human IL-6 (rhIL-6) was administered at high doses to mice, rats, and nonhuman primates. In all species, IL-6 had an immunostimulatory and hemopoietic (especially on megakaryocytes) effect. An acute-phase response was most pronounced in nonhuman primates, which was, however, not associated with any significant histopathological liver change. Finally, no evidence of glomerular pathology was found. Neutralizing antibodies were detected within 10 days of rhIL-6 administration in all species.

Acute-Phase Reaction↗
PubMed1992

Covalent binding of cyclosporine inhibits irreversibly T-lymphocyte activation.

A diazirine derivative of cyclosporine (PL-CS) was used to photolabel recombinant human cyclophilin (rhCyp), the cytosolic receptor for the immunosuppressant cyclosporine. The affinity of PL-CS for rhCyp and the immunosuppressive activity were 10-fold reduced as compared to cyclosporine A. Whereas cyclosporine immunosuppression was fully reversible, UV cross-linking of PL-CS resulted in permanent inhibition of lymphocyte activation as shown by proliferation of anti-CD3 stimulated human peripheral lymphocyte, interleukin (IL)-2 gene transcription and IL-2 synthesis in the human T-leukemia cell line Jurkat. In vivo photolabeling of viable Jurkat cells revealed that a 21-kDa complex was the major radiolabeled product which was identified as a cyclophilin-cyclosporine complex. In addition, cyclophilin B (25 kDa) and proteins of an unidentified nature at 40, 46 and 60 kDa were observed in Jurkat cells. The cyclosporine-resistant human fibroblast cell line MRC5 displayed a different labeling pattern: cyclophilin B (25 kDa) and a 65-kDa protein were the major labeled products, while the 46- and 60-kDa components were not detectable and cyclophilin was only faintly labeled. In summary, covalent cyclosporine binding caused irreversible lymphocyte inactivation and revealed in addition to cyclophilin other specifically labeled proteins in lymphoid cells. The role and identity of these proteins is presently unknown.

Affinity Labels↗
PubMed1992

Identification of several cyclosporine binding proteins in lymphoid and non-lymphoid cells in vivo.

The immunosuppressant cyclosporine A (CSA) has been shown to bind to the ubiquitous cellular protein, cyclophilin, and to inhibit its rotamase activity. In the present study, 3H-cyclosporine diazirine analogue was used to photolabel viable human cells of lymphoid and fibroblast origin in order to identify the intracellular targets for the drug. While cyclophilin was strongly labeled in situ, additional minor cyclosporine-protein complexes of 25, 40, 46 and 60 kDa were identified in the T cell leukemia cell line Jurkat. These proteins bound specifically, since only active CSA but not inactive CSH or FK506 competed for binding. Photolabeling of MRC5 cells, a CSA resistant human fibroblast cell line, revealed a 25 kDa complex as the major product, while the 46 and 60 kDa bands were not detectable and cyclophilin labeling was only faint, even though both MRC5 and Jurkat cells contain similar cyclophilin concentrations. Thus, our data suggest that the intracellular targets of CSA and/or the accessibility to cyclophilin varies considerably in drug sensitive and resistant cell types, which may contribute to explaining the lymphocyte selectivity of the drug.

Amino Acid Isomerases↗
PubMed1992

The carcinogenicity of ciclosporin.

Experimental data relevant for the evaluation of the carcinogenic potential of the immunosuppressant ciclosporin are reviewed: Firstly, the mode of action of ciclosporin at the level of lymphocyte gene transcription, secondly, the main adverse effects especially nephrotoxicity and thirdly, the results of the chronic bioassays. The experimental data are discussed together with the clinical evidence of increased incidence of tumors, especially lymphoproliferative disorders under ciclosporin immunosuppression. Conventional immunosuppression (azathioprine, anti-lymphocyte globulin, prednisone) also demonstrates comparable risks to develop tumors. Lympho-proliferative lesions regress after dose reduction or cessation of treatment. Furthermore, combinations of various immunosuppressants may result in a higher incidence of viral infection and malignancy. In summary, chemical immunosuppression carries the intrinsic risk of tumor growth. In the case of ciclosporin, which has no direct genotoxic effect, tumor promotion is probably dose-dependent. Thus, the risk may be reduced by low dosage and by avoiding combination therapies with additional immunosuppressants.

Animals↗