The usage of alternative splice sites in Mus musculus synaptotagmin-like 2 gene is modulated by cyclosporin A and FK506 in T-lymphocytes.

Cyclosporin-A and FK506 block the calcineurin activity preventing the transcription of genes sharing NFAT-like binding sequences in their promoter region. We presently show that activation of murine T-cells in presence of these immunosuppressors results in the up-regulation of the synaptotagmin-like 2 gene. However, of the four known isoforms, only mRNAs encoding the a and b isoforms accumulate.

T lymphocyte activation initiates the degradation of the CD62L encoding mRNA and increases the transcription of the corresponding gene.

Following T-cell activation, CD62L, a member of the selectin family of cell adhesion molecules, is proteolytically cleaved by a constitutive endoprotease and subsequently re-expressed. To define whether the cleavage regulates CD62L gene transcription, we have analyzed the outcome of T-cell activation on the level of CD62L gene transcription and mRNA stability. Here, we report that CD62L shedding correlates with the concomitant upregulation of CD62L gene transcription and the rapid degradation of the corresponding mRNA.

Characterization of a gene encoding two isoforms of a mitochondrial protein up-regulated by cyclosporin A in activated T cells.

Cyclosporin A (CSA) is an immunosuppressor used in organ transplantation. A recent proteomic analysis has revealed that activation of T cells in the presence of CSA induces the synthesis of hundreds of new proteins. Here we used representational difference analysis to characterize some of the corresponding induced genes.

New aspects of cyclosporin a mode of action: from gene silencing to gene up-regulation.

Cyclosporin A (CSA) has transformed clinical transplantation, both in term of success and of quality-of-life of the patient. Studies aimed to unfold the site of CSA action have shown that this molecule binds to cytosolic proteins of the cyclophilin family. CSA:cyclophilin complexes have a high affinity for calcineurin, a key enzyme in T-cell activation.

Cyclosporin A therapy differently affects immunological-relevant gene expression following immunization.

We have studied the effect of cyclosporin A (CSA) on the expression of genes involved in the immune response in mice bearing a transgenic T cell receptor specific for the peptide 88-104 of the pigeon cytochrome c. Immunization of mice treated with CSA resulted in the blockade of the IL2, IFN-gamma, CXCR-5, CCR-5 and CD25 gene transcription. CSA decreased the density of CD69 on T-cells but did not interfere with the induction of the chemokine receptors CCR-1, CCR-4, CXCR2 and CXCR-4.

Cytokine fields and the polarization of the immune response.

Certain cells that participate in the immune response are known to become polarized in their production of cytokines. It is postulated that, after initial polarization at the site of antigenic encounter, the different types of cell arriving at this site are induced to conform to the local cytokine field, implying that they share common regulatory circuits. As they migrate, these cells might, in turn, spread the particular cytokine field.

Fruit-specific lectins from banana and plantain.

One of the predominant proteins in the pulp of ripe bananas (Musa acuminata L.) and plantains (Musa spp.) has been identified as a lectin.

Increased protein synthesis after T cell activation in presence of cyclosporin A.

Background: The immunosuppressive drug, cyclosporin A (CsA), blocks immune responses by inhibiting the calcineurin-dependent dephosphorylation of the nuclear factor of activated T cells (NFAT). We have previously reported that T cells activated in presence of CsA exhibit particular properties. In our study, we have tested the hypothesis that T cells activated in presence of CsA display a differential pattern of gene expression.

Crystal structure of Urtica dioica agglutinin, a superantigen presented by MHC molecules of class I and class II.

Background: Urtica dioica agglutinin (UDA), a monomeric lectin extracted from stinging nettle rhizomes, is specific for saccharides containing N-acetylglucosamine (GlcNAc). The lectin behaves as a superantigen for murine T cells, inducing the exclusive proliferation of Vbeta8.3(+) lymphocytes.

Isolation and characterization of a jacalin-related mannose-binding lectin from salt-stressed rice (Oryza sativa) plants.

A novel plant lectin was isolated from salt-stressed rice (Oryza sativa L.) plants and partially characterized. The lectin occurs as a natural mixture of two closely related isoforms consisting of two identical non-covalently linked subunits of 15 kDa.

Proteomic analysis of T cell activation in the presence of cyclosporin A: immunosuppressor and activator removal induces de novo protein synthesis.

Cyclosporin A (CsA), a fungal metabolite used in organ transplantation, blocks the immune responses by interfering with early activation signals preventing the induction of the IL2 gene. We have previously reported that the removal of the immunosuppressor provokes the transcription of the IL2 encoding gene. We have now investigated whether the transcription and translation of other genes accompanies this process.

The impact of immunosuppressive drugs on the analysis of T cell activation.

The discovery of the immunosuppressive properties of cyclosporin A (CSA) and its successful utilisation in organ transplantation was a milestone in clinics. CSA has revolutionised transplantation both in term of efficiency and quality-of-life of the patient. In addition, the analysis of the mode of action of CSA has been rewarding in the understanding the mechanisms leading to T lymphocytes activation.

Major histocompatibility class I molecules present Urtica dioica agglutinin, a superantigen of vegetal origin, to T lymphocytes.

The Urtica dioica agglutinin (UDA) shares with the superantigens the property of activating T cell subsets bearing particular Vbeta segments of the TCR. However, UDA is a lectin capable of binding to many glycoproteins on cell membranes. The implication of MHC versus other glycoproteins in UDA presentation was presently studied.

Administration to mouse of endotoxin from gram-negative bacteria leads to activation and apoptosis of T lymphocytes.

Lipopolysaccharide (LPS) from gramnegative bacteria is a well-known T cell-independent B lymphocyte mitogen and macrophage/monocyte activator. While the conventional view holds that LPS is ignored by T cells, we report here that administration of LPS to mice activates all B cells, but also engages most CD4 and CD8 T cells, as measured by the expression of the activation markers CD69 and CD25 and by size increase. T cells recruited in endotoxin-treated mice showed, following in vitro stimulation by concanavalin A, altered patterns of cytokine production.

Th1 response in Salmonella typhimurium-infected mice with a high or low rate of bacterial clearance.

Previous studies have shown that the capacity to clear an attenuated strain of Salmonella typhimurium after the second week of infection varies widely among mouse strains. Bacterial clearance is mediated by CD4+ T cells and is regulated in part by the H-2 complex. The aim of the present study was to compare the patterns of cytokine mRNA expression in the spleens of C57BL/6 (H-2b) and CBA (H-2k) mice, which exhibit a low and a high rate of bacterial clearance, respectively.

Isolation of a novel plant lectin with an unusual specificity from Calystegia sepium.

A novel plant lectin has been isolated from the rhizomes of Calystegia sepium (hedge bindweed) and partially characterized. The lectin is a dimeric protein composed of two identical non-covalently linked subunits of 16 kDa. Hapten inhibition studies indicate that the novel lectin is best inhibited by maltose and mannose and hence exhibits a sugar binding specificity that differs in some respects from that of all previously isolated plant lectins.

Colchicum autumnale agglutinin activates all murine T-lymphocytes but does not induce the proliferation of all activated cells.

Plant lectins with mitogenic properties for T-lymphocytes have been particularly useful for the study of T-cell activation and effector functions. In the search for mitogenic lectins possessing activation features different from the ones associated with the already known mitogens, we found that an agglutinin isolated from Colchicum autumnale tubers, Colchicum autumnale agglutinin (CAA), possesses interesting properties. First, contrasting with the classical mitogens, CAA induces the proliferation of a fraction of the CD4+ and CD8+ mouse T-lymphocytes.

Urtica dioica agglutinin, a V beta 8.3-specific superantigen, prevents the development of the systemic lupus erythematosus-like pathology of MRL lpr/lpr mice.

The V beta 8.3-specific superantigenic lectin Urtica dioica agglutinin (UDA) was used to delete the V beta 8.3+ T cells in MRL lpr/lpr mice.

T cell activation by concanavalin A in the presence of cyclosporin A: immunosuppressor withdrawal induces NFATp translocation and interleukin-2 gene transcription.

Cyclosporin A (CSA), an immunosuppressive agent used in organ transplantation and to treat some autoimmune diseases, blocks the Ca2+-dependent steps involved in T cell receptor triggering leading to interleukin (IL)-2 production. Considering that the early steps of T cell activation are insensitive to CSA, we asked whether the initial activation achieved in presence of this immunosuppressor could affect the capacity of the T cell to respond to a mitogenic restimulation. We found that T cells activated by concanavalin A (ConA) for 48 h in the presence of CSA retain the capacity to proliferate in response to ConA once the immunosuppressor is removed.

V beta-specific deletion of mature thymocytes induced by the plant superantigen Urtica dioica agglutinin.

Urtica dioica agglutinin (UDA), a plant protein, is a superantigen activating in a MHC class II-restricted manner the V beta 8. 3-bearing T-cells (Galelli and Truffa-Bachi, J. Immunol.

Opposite effects of interleukin-4 on memory T helper cell development depend on interleukin-2.

We previously reported that cyclosporin A (CSA) promotes the generation of T helper memory cells during antigenic priming of murine spleen cells in vitro. More recently, we have demonstrated that interleukin-2 (IL2) has a downmodulating effect on T helper memory cell generation. The present data address the role of the other T cell growth factor, IL4, upon induction of these cells.

Gamma interferon and interleukin-10 gene expression in innately susceptible and resistant mice during the early phase of Salmonella typhimurium infection.

Previous studies have shown that gamma interferon (IFN-gamma) plays a major role in natural resistance to Salmonella typhimurium during the early phase of infection. To assess whether the level of natural resistance in mice is related to the level of IFN-gamma gene expression, we compared IFN-gamma mRNA levels by means of reverse transcriptase-PCR in the spleens of genetically susceptible Itys (C57BL/6 and BALB/c) and resistant Ityr (CBA and DBA/2) mice during the first 5 days of infection. The mRNA expression of interleukin-10 (IL-10), a cytokine which antagonizes IFN-gamma effects, was also investigated.

The J beta segment of the T cell receptor contributes to the V beta-specific T cell expansion caused by staphylococcal enterotoxin B and Urtica dioica superantigens.

We have used a new polymerase chain reaction-based technique to analyze at the clonal level the CDR3 diversity and the J beta usage associated with the V beta-dependent T cell receptor (TCR) recognition of two superantigens: the staphylococcal enterotoxin B and the Urtica dioica agglutinin. Our results show that subset of J beta elements is preferentially expanded in a given V beta family, independently of the nature of the superantigen. By contrast, the CDR3 loop does not contribute significantly to the T cell expansion induced by the superantigens.

Interleukin-2 down-modulates memory T helper lymphocyte development during antigenic stimulation in vitro.

Using an in vitro antigenic stimulation model of murine spleen cells in the presence of the immunosuppressor cyclosporin A (CSA) we have previously reported that not only does this drug not interfere with the differentiation of T lymphocytes into memory cells it appears to favor this differentiation (Motta, I. et al., Eur.