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J Urbain

Publications and source records attributed to J Urbain.

At least 19 recordsLinked to original sources
PubMed1992

Antigen-pulsed dendritic cells can efficiently induce an antibody response in vivo.

The aim of this study was to develop an immunization procedure avoiding external adjuvant. Data are presented showing that syngeneic dendritic cells (DC), which have been pulsed in vitro with antigen, induce a strong antibody response in mice. By contrast, antigen (Ag)-pulsed low-density B cells, although equally able to induce interleukin 2 secretion by an Ag-specific T cell hybridoma in vitro, only weakly prime the mice in vivo. Moreover, we show that the injection of Ag-pulsed DC induces the synthesis of isotypes similar to the immunoglobulin classes detected after immunization with the same Ag in complete Freund's adjuvant. Importantly, high amounts of IgG2a antibodies are produced, suggesting that T helper type 1 cells are activated. Collectively, these data indicate that DC can initiate a primary humoral response and that they may be used as physiological adjuvant in vivo.

Animals↗
PubMed1992

The injection of deaggregated gamma globulins in adult mice induces antigen-specific unresponsiveness of T helper type 1 but not type 2 lymphocytes.

Injection of adult mice with high doses of monomeric human gamma globulins (dHGG) has been previously shown to produce a state of peripheral tolerance in both B and T cells. To gain insight into the mechanism of induction and maintenance of adult tolerance in this model, we have analyzed the pattern of lymphokines produced by control and tolerant animals in response to the tolerogen. The data presented indicate that HGG-specific, interleukin 2 (IL-2)- and interferon gamma (IFN-gamma)-producing T cells (thus referred to as T helper type 1 [Th1] cells) are rendered unresponsive after in vivo administration of soluble HGG. In contrast, antigenic stimulation of T cells isolated from tolerant adult mice leads to increased production of IL-4 in vitro. In vivo challenge of dHGG-treated adult animals with hapten-coupled HGG (p-azophenylarsonate [ARS]-HGG) induced a significant ARS-specific antibody response, suggesting that tolerance induction in this model does not completely abrogate tolerogen-specific Th activity in vivo. In agreement with the in vitro data, hapten-specific antibody response of tolerant animals is characterized by a selective deficiency in the IFN-gamma-dependent IgG2a subclass. Injection of immunogenic forms of HGG into tolerant animals also produced an IL-4-dependent increase in total serum IgE levels, indicative of an increased activity of HGG-specific Th2 cells in these animals. The finding that tolerance induction differentially affects Th subpopulations suggests that crossregulation among lymphocyte subsets may play a role in the induction and/or maintenance of acquired tolerance in adults.

Animals↗
PubMed1992

Role of the transmembrane and cytoplasmic domains of surface IgM in endocytosis and signal transduction.

The cross-linking of membrane IgM (mIgM) triggers the activation and differentiation of B lymphocytes. One very rapid result of the cross-linking is the activation of phospholipase C, the subsequent mobilization of free calcium from internal stores and the activation of protein kinase C. This is followed by a redistribution of the receptor-ligand complexes to a small cap on the B cell surface, the first step in endocytosis and antigen processing. Cross-linking of major histocompatibility complex (MHC) class I neither stimulates the release of intracellular calcium nor does it induce capping and endocytosis of the cell surface receptors. In this study, we sought to determine the role of the two carboxyterminal domains of the mu heavy chain in signal transduction, capping and endocytosis of mIgM. We took advantage of the clear differences between MHC class I molecules and mIgM, replacing the transmembrane and cytoplasmic domains of mu by their MHC class I equivalents. Our results show that the hybrid heavy chain could still associate with light chains and assemble into a tetramer on the cell surface. However, cross-linking of the hybrid cell receptor produced neither release of calcium from internal stores, nor capping and endocytosis. These observations demonstrate that the two carboxy-terminal domains of mu are critical to both signal transduction and modulation of the mIgM-ligand complexes from the surface of B lymphocytes.

Calcium↗
PubMed1992

On the kinetics and optimal specificity of cytotoxic reactions mediated by T-lymphocyte clones.

Using the chromium release assay and the single cell assay in agarose, we study the cytotoxic reaction of the MHC-restricted T lymphocyte clones P89:15 and P1:3, which recognize distinct but specific tumour antigens on the surface of syngeneic P815 mastocytoma cells. We propose a mathematical model which describes these experiments, accounts for the strongly non-Michaelian behaviour of the reaction and permits us to estimate the kinetic parameters characterizing effector-target conjugation and lethal hit delivery. The results show that the binding and lytic activity of effector cells is modulated by the number of targets bound to them. The binding of a second target by an effector having already a target bound is facilitated; on the other hand, an effector having bound two targets delivers a lethal hit more slowly than one with a single target bound. We investigate the role of these kinetic properties in the competition between the process of tumour progression due to cancer cell replication and the process of tumour regression due to T lymphocyte cytotoxic activity. For both clones, we estimate the effector-target ratio beyond which rejection prevails. This ratio is nine times larger for P1:3 than for P89:15. Furthermore, our analysis suggests that there exists an optimal specificity minimizing this ratio. Deviations from this optimum, be it in the sense of an increase or decrease of specificity, tends to stabilize the tumoural state: a situation which in the broader context of the immune response evolution and regulation can be viewed as an immune response dilemma.

Animals↗
PubMed1991

Cytokine release syndrome induced by the 145-2C11 anti-CD3 monoclonal antibody in mice: prevention by high doses of methylprednisolone.

The hamster mAb 145-2C11 specific for the CD3 complex of murine T lymphocytes shares many properties with OKT3, including the induction of T cell activation. In vivo, the injection of 145-2C11 entails a variety of pathologic changes in relation to the systemic release of cytokines. We tested the effects on this cytokine release syndrome of different doses of methylprednisolone (m-PDS) given at various intervals of time before the 145-2C11 mAb. The administration of high doses of m-PDS (50 mg/kg) 2 to 3 h before the mAb resulted in an almost complete inhibition of the systemic release of TNF-alpha, IL-2, and IL-6. As far as the pathologic changes are concerned, the hypothermia, the acute renal tubular necrosis, and the fatty infiltration of the liver were completely prevented whereas the hypoglycemia was only partially attenuated. The protective effect of m-PDS on the toxicity of 145-2C11 was confirmed by the reduction of the mortality rate among galactosamine-sensitized mice. The inhibition of the release of cytokines by m-PDS did not affect the immunosuppression triggered by 145-2C11 as assessed by the CTL activity against alloantigens measured 48 h after the injection of the mAb. We conclude that the administration of very high doses of glucocorticoids 2 to 3 h before 145-2C11 prevents the release of cytokines and attenuates the acute toxicity of the mAb. Similar protocols could allow mitigation of the cytokine-release syndrome induced by the OKT3 mAb in man.

Animals↗
PubMed1991

An additional hypervariable region encoded by V gene segments occurs in Tcr V beta at a location compatible with its involvement in Tcr active site--a general model for alloreactivity.

The number of V alpha and V beta sequences of T cell receptors now available allows a meaningful analysis of their variability profiles. Variability plots were derived using a modified form of Wu and Kabat's algorithm: variability is not computed as a proportion of the number of different residues occurring at a position, but rather proportionally to the physicochemical differences between the different residues. Results show that the classical hypervariable regions occurring in immunoglobulins also occur in T cell receptors at equivalent positions. Contrary to immunoglobulins the framework of Tcr V regions displays many relatively variable regions and positions. This phenomenon can be connected with the genetic organization of V genes of T cell receptors which seem to avoid any framework homogenization and the resulting gene conversion. More importantly an additional hypervariable region was detected in V beta but not in V alpha. This fourth hypervariable region is located between the second and the D hypervariable CDR. The predicted three-dimensional location of this additional hypervariable region is compatible with a possible role in antigen recognition and therefore also in positive and/or negative selection. Furthermore our data suggest that this fourth hypervariable region is involved in the recognition of superantigens like bacterial enterotoxins. Indeed this additional hypervariable region is not detected when variability is derived using an alignment of the V beta subgroups stimulated by one toxin of S. aureus. Finally we propose a new and simple molecular model to explain alloreactivity as crossreactivity between the universe of shapes (isomers of conformation) of different MHC haplotypes.

Amino Acid Sequence↗
PubMed1991

Tolerance and immune regulation.

Understanding of both the phenomenon of immunological tolerance and the mechanisms by which it is achieved is rapidly advancing, as was evident from a recent meeting. This report summarizes key developments in both T- and B-cell biology.

Animals↗
PubMed1991

Induction of long-term but reversible unresponsiveness after activation of murine T cell hybridomas.

T cell receptor (TCR)-mediated stimulation of murine T cell hybridomas induces cell activation and lymphokine production. We have observed that following productive activation, T cell hybridomas become refractory to a subsequent stimulation. Hyporesponsiveness is long-lasting but reversible, and is not due to reduced receptor expression. It is noteworthy that hyporesponsiveness is cell autonomous, persists in spite of cell division and does not require continuous exposure to ligands. Hyporesponsive cells retain the ability to produce lymphokines in response to pharmacological agents bypassing receptor triggering, indicating that they possess a functional enzymatic machinery for interleukin 2 synthesis and secretion. Reduced phosphatidylinositol hydrolysis was observed in these cells in response to TCR stimulation, suggesting that hyporesponsiveness result from defective transduction of activation signals. The development of unresponsiveness following receptor stimulation resembles desensitization, and may thus play an important role in the regulation of an immune response and in the induction of immune tolerance.

Animals↗
PubMed1991

Hyper IgE in stimulatory graft-versus-host disease: role of interleukin-4.

Intravenous injection of 2 x 10(8) DBA/2 spleen cells into adult intact (C57BL/6 x DBA/2) F1 mice results in a stimulatory graft-versus-host reaction (GVHR) linked to the recognition by donor CD4+ T cells of Ia alloantigens on host B cells. In the experiments presented here, we found that this GVHR is associated with a major increase in IgE serum levels which was already present 7 days after the cell transfer. At 6 weeks, mean IgE levels were more than 200-fold above the control values. Host B cells were responsible for the hypersecretion of IgE in stimulatory GVHR since it was also observed when the DBA/2 donor inoculum was depleted of B cells but not when the F1 recipients were irradiated. The induction of IgE secretion required donor CD4+ T cells as treatment of the donor inoculum with lytic anti-CD4 monoclonal antibody (MoAb) completely prevented the occurrence of the hyper IgE whereas depletion of CD8+ cells had no influence on this parameter. The role played by interleukin-4 (IL-4) in this model was analysed in vivo by the administration of the 11B11 anti-IL-4 rat MoAb (total dose 36 mg) during the first 12 days following induction of stimulatory GVHR by 8 x 10(7) DBA/2 spleen cells. This treatment completely prevented the development of hyper IgE whereas the administration of a control rat MoAb had no significant effect. We conclude that stimulatory GVHR in mice is associated with a major increase in serum IgE which is mediated by IL-4.

Animals↗
PubMed1991

Modulation of murine host-versus-graft disease by anti-CD3 monoclonal antibody.

BALB/c mice made tolerant to A/J alloantigens by neonatal injection of (A/J x BALB/c)F1 spleen cells develop a host-versus-graft (HVG) disease due to the activation of donor B cells by a subset of host alloreactive helper T cells. We have investigated the effects of a single neonatal injection of the 145-2C11 anti-mouse CD3 monoclonal antibody (MoAb) on the establishment of allotolerance and on the development of the immunopathological features of HVG disease. First, this treatment did not modify the specific anti-donor cytotoxic T lymphocyte (CTL) unresponsiveness or the persistence of circulating immunoglobulins bearing donor allotype. Second, the hyper IgE, the hyper IgG1 and the increased expression of Ia antigens on B cells found in untreated HVG mice were not observed after injection of the 145-2C11 MoAb. Likewise, treated mice displayed lower levels of anti-DNA IgG antibodies and less glomerular immune deposits as compared with untreated HVG mice. We conclude that the administration of the anti-CD3 MoAb did not interfere with the induction of allotolerance but exerts a pronounced inhibitory effect on the associated immunopathological syndrome.

Animals↗
PubMed1990

Immune surveillance: both CD3+ CD4+ and CD3+ CD8+ T cells control in vivo growth of P815 mastocytoma.

The aim of this study was to examine whether a spontaneous immune response controls neoplastic growth in P815-bearing DBA/2 mice, and to characterize the cells involved in tumor resistance in vivo. Several cell lineages such as T-cell-receptor (TcR)-bearing T cells, NK cells and macrophages mediate some anti-tumor activity in vitro. P815 was chosen as a model because it is weakly immunogenic and is a good target both for tumor-specific, MHC-restricted CTL-mediated lysis and for MHC-unrestricted lysis exerted by long-term cultured lymphocytes or activated macrophages. Since most "NK-like activity" in freshly isolated populations appears to be associated with CD3- cells, whereas antigen-specific, MHC-restricted T cells mostly express CD3 determinants, CD3 was a good marker for evaluating the role of T cells and "NK" cells in tumor resistance in vivo. The survival of anti-CD3-treated animals that were inoculated with tumor cells was strongly reduced (mean survival time: 17 days vs. 40 days for the control group) and was associated with increased tumor growth rate. We followed the same approach to define the T-cell subset(s) that mediate(s) this immune response. Both CD4+ and CD8+ T cells were required for induction of immune control on neoplastic growth. The approach used has revealed the important role of CD4+ T cells in immune responses that control in vivo growth of a class-I-positive, class-II-negative tumor and suggests that these cells may play a central role in tumor resistance. Since CD4+ cells are activated by soluble, exogenous proteins, this finding may have important implications for immunotherapy.

Animals↗
PubMed1990

Anti-CD3 antibodies induce T cells from unprimed animals to secrete IL-4 both in vitro and in vivo.

Recently, functional heterogeneity among Th cells has been recognized. Based on pattern of lymphokine secretion, two mutually exclusive subsets of CD4+ cells have been defined and designated Th1 (secreting IL-2 and IFN-gamma) and Th2 (secreting IL-4 and IL-5). Identification of these subsets was mostly based on the study of long term cultured T cell lines and clones, and little is known about the Th heterogeneity in vivo. In particular, it has been suggested that IL-4 producing cells cannot be detected in vivo or in primary stimulations in vitro unless responder cells had been previously primed. Our data however, indicate that anti-CD3 mediated stimulation can induce T cells isolated from unprimed animals to IL-4 production. An assay system based on the ability of IL-4 to increase Ia expression of B cells present in the environment of activated T cells was found to be more sensitive than detection of secreted IL-4 in the supernatant by conventional bioassays and was used to study IL-4 production by unprimed lymphocytes polyclonally stimulated in vivo and in vitro by anti-CD3 mAb. The results obtained indicate that CD4+ CD8- T cells able to produce IL-4 upon receptor-specific stimulation exist in the preimmune pool of adult animals. Remarkably, these cells can also be stimulated in vivo by treating animals with anti-CD3 mAb, as indicated by the in vivo induction of IL-4 specific mRNA and hyper-Ia expression on B cells. These results indicate that the inability to detect IL-4 in primary cultures is not due to different activation requirements of Th2 cells but may simply result from their lower frequency in unprimed animals.

Animals↗
PubMed1990

Loss of a major idiotype (CRIA) after repopulation of irradiated mice.

The normal immune response of A/J mice against arsonate coupled to hemocyanin is characterized by a major recurrent cross-reactive Id, the CRIA. This Id is encoded by a single gene segment combination: VHidcr11-DFL16.1e-JH2 for the H chain and Vkidcr-Jk1 for the L chain. In this report, we show that lethal irradiation of A/J mice followed by reconstitution with autologous or syngeneic lymphoid cells results in loss of major CRIA Id expression in the response to arsonate. Different protocols were performed to repopulate the irradiated mice. First, lethally irradiated A/J mice were reconstituted by the transfer of syngeneic bone marrow cells. Second, A/J mice were lethally irradiated while their hind limbs were partially shielded. Third, lethally irradiated A/J mice received a transfer of syngeneic spleen cells. The three groups of mice produce high titers of antiarsonate antibodies completely devoid of CRIA DH-JH related idiotopes expression. Moreover, a lack of affinity maturation is observed in the secondary antiarsonate response of all irradiated and reconstituted mice. A transfer of syngeneic peritoneal cells or a transfer of primed T cells in irradiated and reconstituted A/J mice do not restore in a significant manner either the recurrent CRIA expression or the affinity maturation of the antiarsonate response. Our data suggest that the choice of this Id is not solely dictated by the Igh locus.

Animals↗
PubMed1990

Hypothermia and hypoglycemia induced by anti-CD3 monoclonal antibody in mice: role of tumor necrosis factor.

The possible involvement of tumor necrosis factor-alpha (TNF) in the metabolic disturbances induced by anti-CD3 monoclonal antibodies (mAb) was analyzed in DBA/2 mice injected with 50 micrograms of the anti-murine CD3 mAb 145-2C11. First, we found that 145-2C11 induces a profound hypothermia maximal between 3 h and 6 h after the injection (at 3 h: -3.0 +/- 0.1 degrees C) as well as hypoglycemia (blood glucose levels at 6 h and 24 h: 76 +/- 13 mg/100 ml and 92 +/- 22 mg/100 ml, respectively, p less than 0.001 as compared with control values). These metabolic changes are preceded by the release of TNF into the circulation (peak serum TNF levels at 2 h: 50 +/- 23 pg/ml, p less than 0.01 as compared with controls). The release of TNF induced by 145-2C11 depends on the effect of the mAb on T cells as it is not observed in athymic nude mice while lipopolysaccharide-resistant C3H/HeJ mice also display a significant rise in serum TNF (peak levels at 2 h: 59 +/- 44 pg/ml). Pretreatment of DBA/2 mice with 12 mg of rabbit anti-murine TNF antibodies completely prevents the hypothermia while the hypoglycemia is significantly attenuated. Finally, F(ab')2 fragments of 145-2C11 induce only a transient hypoglycemia (blood glucose levels at 6 h: 109 +/- 14, p less than 0.001 as compared with controls) but neither hypothermia nor significant TNF release. We conclude that TNF is a major mediator of the acute metabolic changes induced by the intact form of 145-2C11.

Animals↗
PubMed1990

A private idiotype can become recurrent through genetic recombination and gene(s) unlinked to the Igh locus governs its expression.

Any immune response is characterized by its idiotypic profile. Two different kinds of idiotype (Id) have been described. Private Id are restricted to a few individuals from a species while recurrent Id appear in a large majority of individuals from the same species immunized with the same antigen. We describe, in this report, an experimental model whereby a private Id can become recurrent through genetic recombination. The immune response of A mice against the hapten arsonate is characterized by a recurrent Id called cross-reactive idiotype A (CRIA). A strongly CRI, called CRIA-like, can be occasionally detected in some BALB/c mice (5% to 10%) immunized with arsonate. Molecular studies show that CRIA and CRIA-like antibodies have highly homologous D segments and identical light chains. By contrast, their VH segments are vastly dissimilar. We have examined the anti-arsonate response of inbred strains of mice whose Igh loci are recombinant between those of A/He and BALB/c. Interestingly, we have observed that the CRIA-like Id which is private in BALB/c becomes recurrent in the AXC-1 strain which harbors the VH genes from BALB/c, the DH and CH genes from A/He. Structural studies demonstrate that highly homologous, VH, VL and D segments are used in BALB/c and AXC-1 mice. The basis for this differential expression of highly similar genes could be linked to the DH locus. However, F1 mice stemming from the cross between AXC-1 and BALB/c do not express the Id. The backcross analysis shows that the non-expression of the Id in F1 mice depends on genes unlinked to the Igh locus.

Animals↗
PubMed1989

Structural characterization of antiidiotypic antibodies. Evidence that Ab2s are derived from the germline differently than Ab1s.

We have found that syngeneic Ab2s in the antiarsonate system are serologically and structurally similar to one another. In contrast, the allogeneic Ab2 response is heterogeneous and derives from a large number of unrelated germline gene segments. The Ab2 response of the BALB/c strain to polyclonal A/J Ars A molecules can probably best be compared with a response to a foreign protein and might have been predicted in a strain that completely lacks the H chain V region gene from which the Ab1 derives. Partial variable region sequences of Ab2s from three other systems in addition to previously reported Ab2 structures indicates that this difference in allogeneic vs. syngeneic Ab2s may be a general phenomena. These data support Jerne's hypothesis of complementary V region genes existing in the germline. However, there is good evidence that these antiidiotypic antibodies are not derived directly from the germline, as somatic processes most likely play an important role in their generation. The D segments of Ab2s in the arsonate system as well as in other systems, are novel in structure and cannot easily be explained by previously described germline D segments. D-D fusion may play a role in the generation of the third hypervariable region in these antibodies.

Amino Acid Sequence↗
PubMed1989

Detection of rotavirus in faecal specimens with a monoclonal antibody enzyme-linked immunosorbent assay: comparison with polyclonal antibody enzyme immuno-assays and a latex agglutination test.

Monoclonal antibodies have been produced against the 81/36F strain of rotavirus. One of them, was chosen as diagnostic reagent: it showed high ELISA reactivity with all the bovine, human and porcine rotavirus strains tested and reacted with VP6, structural protein product known to support the common rotavirus antigen. A sandwich ELISA procedure using the chosen monoclonal as "capture and detecting" antibody was performed to detect rotavirus in faecal samples from experimentally inoculated newborn calves: it always gave a negative response with meconium and a positive response for the stool specimens which rotavirus have been isolated. This assay was compared with Enzygnost and Slidex Rota Kit tests and with a non-commercial sandwich ELISA test using polyclonal antibodies: it showed more sensitivity than the agglutination test and was as sensitive as the other two tests to detect rotavirus in routine diagnostic material. The test evaluated showed no equivocal results.

Animals↗