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H Bazin

Publications and source records attributed to H Bazin.

At least 19 recordsLinked to original sources
PubMed1995

Lack of L-selectin expression by cells transferring diabetes in NOD mice: insights into the mechanisms involved in diabetes prevention by Mel-14 antibody treatment.

The process of mononuclear cell extravasation from the blood into the islets of Langerhans in nonobese diabetic (NOD) mice is dependent on the expression of a set of molecules, most of which remain to be defined. The observation that vascular addressins are expressed in inflamed islets raises the issue of the involvement of one of their ligands, L-selectin, in the pathogenesis of autoimmune diabetes. Treatment of NOD females with Mel-14, an antibody specific for L-selectin, reduced the spontaneous development of both insulitis and diabetes. Pretreatment of diabetic donors with Mel-14 decreased the capacity of their splenocytes to transfer the disease. However, the treatment of recipients had no effect on the transfer of diabetes by untreated diabetogenic splenocytes. To reconcile these apparently conflicting results, we fractionated spleen T cells from diabetic mice according to L-selectin expression. Diabetogenic cells were found only in the L-selectin subpopulation. Thus, diabetogenic cells in adult mice share phenotypic characteristics with activated/memory cells, and enter the pancreas using L-selectin-independent migratory pathways.

Animals↗
PubMed1995

A rat monoclonal anti-(human CD2) and L-leucine methyl ester impacts on human/SCID mouse graft and B lymphoproliferative syndrome.

The transfer of human peripheral blood mononuclear cells (hu-PBMC) from adult Epstein-Barr-virus(EBV)-seropositive donors in SCID (severe combined immunodeficiency) mice frequently leads to the development of a human B lymphoproliferative syndrome (hu-BLPS). Therefore, as 90% of adult potential donors are EBV-seropositive, efforts have to be made to avoid the occurrence of this B lymphoproliferative disorder. McCune et al. [Science 241:1632 (1988)] used human fetal organs for a human SCID graft. This system does not give rise to hu-BLPS but human fetal organs are much less available than peripheral blood leucocytes. The experiments reported in this paper show how crucial is the presence of functional T lymphocytes for a graft to take and for development of hu-BLPS in hu-PBMC-reconstituted SCID mice, since inhibition of T lymphocyte by a rat anti-(human CD2) monoclonal antibody (LO-CD2a) during the first 10 days of the graft prevents successful engraftment of human normal lymphocytes as well as hu-BLPS in SCID mice. The transfer of B cells alone or B cells plus monocytes in SCID mice does not permit either long-term engraftment or development of hu-BLPS. We also demonstrate that hu-PBMC treated with L-leucine methyl ester are less susceptible to the development of hu-BLPS after engraftment in SCID mice than are untreated hu-PBMC. The mechanism of action of L-leucine methyl ester on these cells is discussed.

Animals↗
PubMed1995

Induction of Th2 responses to soluble proteins is independent of B cell tolerance status.

Injection of high doses of monomeric human gamma globulins (dHGG) in naive, adult mice causes antigen-specific tolerance of B cell and Th1 lymphocytes, while inducing the selective expansion of antigen-specific Th2 cells. Several parameters of tolerance induction were analyzed in this work, in order to establish whether B cell tolerance and Th1 unresponsiveness were functionally related in this in vivo model. By varying the antigen form and site of injection, we demonstrate in this work that Th1 unresponsiveness to HGG is not a consequence of peripheral B cell tolerance. In particular, mice pretreated with heat-aggregated antigen (HAHGG) or F(ab')2 HGG were found to develop a strong humoral response while displaying a defective Th1 response. In fact, these animals developed a strong Th2 response in vivo, demonstrating that selective expansion of antigen-specific Th2 cells in this model is not a consequence of B cell tolerance or antigen capture by Fc receptor-expressing cells. We conclude that while B cell tolerance in this model is only observed in response to deaggregated antigen, injection of all forms of adjuvant-free, protein antigens induces T helper precursor cells to differentiate into Th2-type helper cells in vivo irrespectively of the B cell tolerance status.

Animals↗
PubMed1994

Preformed antibody and complement rebound after plasma exchange: analysis of immunoglobulin isotypes and effect of splenectomy.

UNLABELLED: Splenectomy (Sx) has been proposed to attenuate post-PE (plasma exchange) rebound of isoagglutinins and xenogenic (XG) antibody (Ab) in both ABO-incompatible allografts and discordant xenografts. This study analyses the qualitative nature and kinetics of serum immunoglobulins as well as complement resynthesis after PE in sham-operated (PE) and splenectomized (PE+Sx) syngeneic LOU/C rats; non-PE sham-operated or splenectomized animals were used as controls. PE was performed in unanesthetized, unheparinized rats. Immunoglobulin isotypes and subclasses (IgM, IgG1, IgG2 alpha, IgG2b) of total circulating Ab were measured pre-PE and up to 21 days post-PE, using ELISA (enzyme-linked immunosorbent assay) and specific mouse antirat monoclonal Ab. Antiguinea-pig (GP) XG Ab (IgM, IgG2a) serum levels were measured using cellular ELISA with cultured GP endothelial cells as targets. Sx alone significantly reduced XG IgM serum levels (p < 0.0001). Maximal rebound of total and XG IgM was observed on day 3 post-PE, reaching 674% and 187% of the pre-PE levels, respectively; these overshoots were entirely suppressed by Sx (p < 0.005 for total IgM; p < 0.0001 for XG IgM). Total IgG2a, IgG2b and IgG1 as well as XG IgG2a serum levels did not show significant overshoot post-PE. The activity of the complement classical pathway (mean +/- SD), assessed by CH50, was decreased at 51 +/- 19% of basal value 15 minutes after PE, and had returned to baseline level by day 2 post-PE with or without Sx. IN CONCLUSION: (1) Six alone significantly reduced XG IgM serum levels; (2) early post-PE Ab rebound was mainly observed for IgM; (3) both total and XG IgM rebound was inhibited by Sx. This suggests that Sx probably removes a significant proportion of IgM producing cells undergoing post-PE stimulation. These data provide a rationale for combining PE with Sx in ABO-incompatible and discordant XG transplantation.

Animals↗
PubMed1994

Trypanosoma cruzi infection in mice induces a polyisotypic hypergammaglobulinaemia and parasite-specific response involving high IgG2a concentrations and highly avid IgG1 antibodies.

Trypanosoma cruzi infection in BALB/c mice induced a reversible polyisotypic hypergammaglobulinaemia, with particularly high levels of IgG2a, IgM and IgE. Hypergammaglobulinaemia started during the acute phase of infection and persisted during chronic disease until 11-13 weeks post-infection (w.p.i.), when immunoglobulin levels, with the exception of IgE, returned near normal values. Parasite-specific antibodies counted for 14 to 23% of gammaglobulinaemia, in acute and chronic infection respectively. The titres of IgM antibodies rose from two w.p.i. IgA, IgE and IgG subclass antibodies built up gradually over the time of parasite clearance (i.e., between three and six w.p.i.). All antibody isotypes, including IgM reached significant and stable titres throughout chronic infection. IgG2a, IgG1 and IgM antibodies had constantly higher titres than the other antibody isotypes. The dominance of IgG2a antibodies was due to their high plasma concentrations, around 70% of all antibodies available in the chronic infection. IgG1 had the highest functional avidity, whereas its concentration corresponded to only 10% of the whole antibody fraction. These results indicate that T. cruzi infection in mice induces a polyisotypic humoral immune response, dominated by some antibody isotypes, with major differences in concentrations and functional avidities. This could be of crucial importance in determining the outcome of infection.

Animals↗
PubMed1994

In vivo study of mIgM and mIgD cross-linking on murine B cells.

In this study, we have analysed in mice the effects on the immune response of in vivo treatment with different rat monoclonal antibodies (MoAb) against IgM and IgD. Although the effects of IgD cross-linking have been studied already, no attempt has been made to characterize the effects of in vivo IgM crosslinking, probably because of the higher IgM serum levels compared to IgD. We have used a panel of nine monoclonal rat anti-mouse IgM and three anti-IgD antibodies and we have characterized their isotypes, avidities, immunoglobulin (Ig) cross-linking and internalization abilities. Our results show that injection of mice with some rat MoAb against IgM led to an important decrease of IgM serum level and internalization of membrane IgM (mIgM) on almost all B cells. Similarly, treatment with a high-avidity anti-IgD antibody induced disapperance of mIgD on B cells. Treatment with rat MoAb against IgM or IgD led to a synthesis of specific antibodies and there was a direct relationship between the Ig internalization abilities of rat MoAb and the induction of specific antibody production. Finally, treatment with a high-avidity rat MoAb against IgD induced a polyclonal IgE and IgG1 secretion. The significance of these results on mIg receptor functions is discussed.

Animals↗
PubMed1994

Depletion of IgM xenoreactive natural antibodies by injection of anti-mu monoclonal antibodies.

It is believed that IgM xenoreactive natural antibodies (XNA) and activation of complement are the two main effectors involved in the hyperacute rejection (HAR) of discordant xenografts, such as pig-to-primate kidney, liver or heart transplants. We have hypothesized that long-term depletion of circulating IgM XNA might be able to overcome HAR and induce the "accommodation" of pig-to-primate vascular discordant xenografts. Several techniques have been described to eliminate circulating XNA in primates but, up to now, none has been able to totally deplete these antibodies for a sufficiently long period of time in order to test the hypothesis of discordant xenograft "accommodation". Previous reports from our laboratory have shown that, in rodents, B-cell immunosuppression could be achieved by neonatal administration of anti-mu antibodies. Recently we have shown that administration of an anti-mu mAb, in adult rats, was able to totally deplete circulating IgM and IgM XNA, without immune complex disease. Furthermore, we have used different methods such as splenectomy, plasma exchange and an anti-B cell immunosuppressive agent mycophenylate mophetil (RS61443, Syntex, Palo Alto, USA) to pre-deplete circulating IgM before administration of anti-mu mAb (MARM-7) and showed that the effectiveness of anti-mu mAb to deplete circulating IgM was increased by 100-fold. Depletion of circulating IgM in adult rats by anti-mu mAb (MARM-7) was used as an experimental model to study the role of IgM XNA in the pathogenesis of HAR in guinea pig-to-rat cardiac xenografts. Our data show that IgM XNA play a major role in HAR, even if in this discordant combination direct activation of complement, probably through the alternative pathway, seems to be the main effector involved in HAR. We have analyzed the mechanisms of anti-mu depletion of circulating IgM in adult animals and shown that, besides anti-mu/IgM immune complex formation, depletion of circulating IgM results from the very significant inhibition of B-cell differentiation and secretion of IgM following in vivo crosslinking and internalization of surface IgM on B cells. As well, we provide evidence demonstrating that anti-mu mAb blocks B cells at an early stage of maturation, probably in the bone marrow. Furthermore, we have developed several rat anti-human and anti-baboon IgM mAb and tested their ability to deplete circulating IgM and IgM XNA in baboons, after splenectomy or splenectomy and plasma exchange.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

A rapid and efficient purification method for horse IgG(T) using a rat monoclonal antibody.

1. Louvain rats (IgK-1a) were immunized with horse IgG(T). To generate mAb to IgG(T), popliteal lymph node cells taken from the immunized animals were fused to a non-secreting LOU/C immunocytoma (IR983F). The hybridomas were cultured in HAT-containing medium and cloned under limiting dilution conditions. Supernatants from the growing hybrids were screened by ELISA using plates coated with horse IgG(T) or IgGa+b+c. 2. The anti-IgG(T) mAb obtained was named LO-HoGT-1 (LOU anti-horse IgG(T)). It is an IgG2a rat antibody whose light chain allotype is IgK-1a, and with an affinity constant of 2.9 x 10(10) M-1. 3. Ascites was induced in LOU (IgK-1b) rats by injecting the hybridoma cells and incomplete Freund's adjuvant ip. To obtain purified mAb, ascitic fluid was applied to a Sepharose anti-rat LOU IgK-1a chain column. 4. The purified mAb was then coupled to Sepharose. Immunoelectrophoretically pure IgG(T) was obtained by passage of horse serum through this column. The entire procedure took less than 30 min and resulted in a highly purified IgG(T).

Animals↗
PubMed1992

Chemical synthesis of a biologically active natural tRNA with its minor bases.

The complete chemical synthesis of an E. coli tRNA(Ala) with its specific minor nucleosides, dihydrouridine, ribothymidine and pseudouridine, is reported. The method makes use of protected 2'-O-tertiobutyldimethylsilyl-ribonucleoside-3'-O-(2-cyanoethyl-N- ethyl-N- methyl)phosphoramidites. The exocyclic amino functions of the bases were protected by the phenoxyacetyl group for purines and acetyl for cytosine. The assembling has been performed on a silica support with coupling yield better than 98% within 2 min of condensation. Triethylamine tris-hydrofluoride allowed a clean and complete deprotection of the tBDMS groups. The synthetic tRNA(Ala) has been transcribed into cDNA by reverse transcriptase and sequenced. With E. coli alanyl-tRNA synthetase the alanyl acceptance activity and kcat/Km were 672 pmol/A260 and 6 x 10(4)M-1s-1, respectively.

Alanine-tRNA Ligase↗
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

Modulation of oral tolerance to ovalbumin by cholera toxin and its B subunit.

Oral administration to mice of ovalbumin (OVA), if given together with cholera toxin (CT) or its B subunit (CTB) prevented the hyporesponsiveness to OVA subsequently injected parenterally. Oral immunization with CT plus OVA or OVA plus CTB in fact primed the immune system, inducing a stronger response to a subsequent parenteral injection of OVA with complete Freund's adjuvant than in mice prefed only with OVA or with saline. Oral CT plus OVA also induced good serum IgG1 and IgA anti-OVA responses, with slightly (not significant) decreased IgG2a and IgG2b responses. Our in vivo findings agree well with earlier in vitro data from others, including CT inhibition of the Th1 CD4+ T cell subset and with CT effect on B cells (induction of LPS-stimulated IgM+ B cells to undergo increased switch differentiation to IgG1- and IgA-secreting cells).

Adjuvants, Immunologic↗
PubMed1992

Antibody mediated lysis of hapten-conjugated target cells by macrophages and by complement: the influence of IgG subclass, antibody and hapten density.

Lysis of 51Cr-labeled TNP-SRBC sensitised by rat IgG1 or IgG2a type antibodies by homologous, paraffin oil-elicited peritoneal macrophages (ADCC) or by homologous complement was studied. IgG2a was found to be markedly more efficient in mediating both ADCC and complement dependent lysis compared to IgG1. Inhibition of the ADCC pointed to the involvement of separate but partially overlapping interaction sites for the two isotypes. We suggest that FcRII type receptors play a favoured role in both IgG2a and IgG1 mediated ADCC. The threshold amount of bound antibody required for ADCC was lower than that sufficient for complement dependent lysis regardless on the subclass or on hapten density. The extent of lysis (both ways) was found to depend on hapten density using equal amounts of antibody. The results are interpreted as terms of the possible requirements for association of IgG molecules on the target cell surface.

Animals↗