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P Truffa-Bachi

Publications and source records attributed to P Truffa-Bachi.

At least 37 records · Page 2Linked to original sources
PubMed1995

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. J. Immunol. 1991. 21:551). Because CSA blocks interleukin-2 (IL-2) gene expression, we have analyzed the effect of this cytokine on memory T helper cell development. Murine splenic cells were primed for 6 days with sheep red blood cells (SRBC) in protocols in which either IL-2 was not produced or its biological activity was neutralized by anti-IL-2 receptor (R) antibodies. The helper function of the recovered T cells was revealed by their capacity to help virgin B splenocytes produce anti-SRBC antibodies upon challenge in vitro. We found that CD4+ cells primed in the absence of IL-2, provoked either by IL-2 gene transcription blockade by CSA or by treatment with anti-IL-2R antibodies, afford the best helper functions. These cells exhibit a memory-type phenotype characterized by the low expression of the MEL-14 marker and the high expression of the CD44 marker. Evidence is also presented that memory T helper cells originate in part from naive subset displaying the MEL-14hi phenotype. The pattern of expression of the genes encoding different cytokines (IL-2, IL-4, IL-5 and interferon-gamma) following a secondary antigenic stimulation shows that the helper function of the cells primed in the absence of IL-2 correlates with the up-regulation of the IL-2 and the IL-5 genes. From these data, we conclude that IL-2 plays a major role in the control of memory T helper cell induction.

Animals↗
PubMed1993

Urtica dioica agglutinin. A superantigenic lectin from stinging nettle rhizome.

Urtica dioica agglutinin (UDA) is an unusual plant lectin that differs from all other known plant lectins with respect to its molecular structure and its extremely low specific agglutination activity. We recently reported that this small lectin (8.5 kDa) is a T cell mitogen distinguishable from classical T cell lectin mitogens by its ability to discriminate a particular population of CD4+ and CD8+ T cells as well as its capacity to induce an original pattern of T cell activation and cytokine production. The mechanism by which UDA activates T cells was investigated and compared with the conventional T cell mitogen Con A and the known superantigen staphylococcal enterotoxin B. Our data show that T cell proliferation induced by UDA is strictly dependent on AC expressing MHC class II molecules but is not MHC restricted. This proliferation can be partially inhibited by anti-I-A or anti-I-E mAb and completely blocked by a mAb recognizing monomorphic determinants on the Ia molecule. UDA indeed binds to specific carbohydrate structures present on class II molecules. UDA-induced T cell stimulation is dependent on TCR recognition of the unprocessed intact molecule in association with various Ia molecules. T cell response to UDA is clonally expressed and correlates with particular TCR V beta gene families usage. This stimulation leads to a sixfold enrichment of V beta 8.3+ T cells within 3 days. Therefore, UDA appears to use the same molecular mechanism as structurally unrelated bacterial or retroviral superantigens and we propose that this lectin is a superantigen. UDA, which is not a pathogenicity factor, could provide a useful probe for the analysis of T cell activation by superantigens.

Animals↗
PubMed1993

Altered cytokine genes expression by conA-activated spleen cells from mice infected by lymphocytic choriomeningitis virus.

The intravenous injection of mice with lymphocytic choriomeningitis virus (LCMV) induces a rapid and long-lasting immunodeficiency. T lymphocytes from 7-day-infected mice do not proliferate in vitro in response to ConA stimulation, do not produce IL-2 but display high affinity IL-2 receptors on their membrane. The non-coordinated regulation of these genes suggested that other cytokine-encoding genes may also be affected in their regulation. We have thus analyzed the expression of the genes encoding different cytokines transcribed during spleen cell activation by ConA. The genes encoding T lymphocyte-derived cytokines can be classified in three groups: the genes expressed similarly by normal and LCMV-cells (the p55 and the p75 chains of the IL-2 receptor [1]), the genes under expressed in LCMV-cells (IL-2, IL-3, IL-4 and IL-5) and the genes over expressed by these cells (GM-CSF and IFN-gamma). These results show that the viral infection has provoked a profound alteration of the overall regulation of the genetic program that follows T lymphocyte activation. Since T cell activation depends strictly on accessory cell-derived cytokines, we measured the level of transcription of IL-1, IL-6 and TNF-alpha; and our data show that the expression of these genes is equivalent in normal cells and in cells from LCMV-infected mice.

Animals↗
PubMed1993

High frequency of T lymphocytes committed to interferon-gamma transcription upon polyclonal activation in spleen from lymphocytic choriomeningitis virus-infected mice.

Splenic T lymphocytes from C3H/HeOur mice infected for 7 days with lymphocytic choriomeningitis virus (LCMV) do not proliferate in response to concanavalin A (Con A). Although the IL-2 gene remained silent after polyclonal activation, the gene encoding the p55 chain of the IL-2 receptor was normally transcribed. These data indicated that the co-ordinated expression of the unique wave of cytokine and cytokine receptor expression, associated with T cell triggering, did not occur in T lymphocytes from LCMV-infected mice. In a first attempt to characterize the potential of these cells to initiate the transcription of cytokine genes, we have focused our attention on interferon (IFN)-gamma, a cytokine displaying multifocal activities on the immune response. We found that the IFN-gamma encoding gene, silent before Con A activation, was transcribed after triggering in normal and LCMV-infected cells. Notably, the level of induction was approximately 10-fold higher in LCMV mice than in non-infected control mice. IFN-gamma gene was induced in both CD4 and CD8 subsets. Induction was sensitive to cycloheximide addition and thus required de novo protein synthesis. The high level of IFN-gamma mRNA transcripts was correlated with a high frequency of cells transcribing this gene. By in situ hybridization we showed that the majority (approximately 70%) of the splenic T lymphocyte population were positive for IFN-gamma mRNAs. A matching increase in IFN-gamma protein corresponded to this elevated IFN-gamma mRNA level. This observation revealed the existence in LCMV-infected mice of a preponderant peripheral T lymphocyte population which displayed unusual activation and proliferative characteristics.

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PubMed1992

Mouse T-lymphocyte activation by Urtica dioica agglutinin. I.--Delineation of two lymphocyte subsets.

Urtica dioica agglutinin (UDA) is a mouse T-lymphocyte-specific mitogen endowed with proliferative characteristics different from ConA, the prototypic T-lymphocyte mitogen. In particular, UDA induces 2-3-fold-reduced thymidine incorporation as compared to ConA. In an attempt to define the basis of this reduced proliferation, we analysed whether UDA binds to a unique subset of T lymphocytes or whether it activates only a T-cell subset. Cytofluorimetric analysis showed that this lectin binds uniformly to all T lymphocytes and does not, on this criterion, distinguish a particular T-cell subset. We next analysed whether UDA provokes the activation of all T lymphocytes. This was carried out by measuring the increase in cell size and the induction of the p55 chain of the IL2 receptor. The analysis showed that, throughout the kinetics of cell activation, only one subset of T lymphocytes increased in size and expressed the p55 chain of the IL2 receptor, suggesting that UDA activates only a subpopulation of T cells. This conclusion was strengthened by the analysis of 5-bromo-2-deoxyuridine (BrdU) incorporation into the DNA of UDA-activated cells. Two populations were easily identifiable: a BrdU-negative subset consisting of all the small p55-negative lymphocytes, and a BrdU-labelled subset including all the large p55-positive cells. BrdU was incorporated in both CD4+ and CD8+ cells, indicating that UDA did not distinguish helper from cytotoxic T lymphocytes. In addition to the p55 chain of the IL2R, all cycling cells expressed the Pgp-1 activation marker. The T lymphocytes, which bound UDA but did not proliferate, remained fully susceptible to subsequent stimulation by ConA. In conclusion, the capacity to proliferate upon UDA binding differentiates a UDA-sensitive from a UDA-refractory subset among splenic mouse T lymphocytes.

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PubMed1992

Mouse T-lymphocyte activation by Urtica dioica agglutinin. II.--Original pattern of cell activation and cytokine production induced by UDA.

Urtica dioica agglutinin (UDA) is a T-lymphocyte-specific polyclonal activator that differs from ConA, the classical mouse T-cell mitogen, by inducing a late and limited proliferation of a distinct T-cell subset recruited among both CD4+ and CD8+ lymphocytes. We investigated the possibility that the particular kinetics may originate from UDA-specific activation processes in which the known early mandatory signals were completed only after an extended delay. We report that the time of contact required between lectin and the cell membrane to acquire the capacity to proceed into cell cycle was much longer (36-40 h) for UDA than for ConA (8-10 h). Addition of phorbol ester, which artificially induces PKC translocation, or ionomycin, which provokes Ca2+ mobilization, did not accelerate the proliferative kinetics, suggesting that these early mandatory signals are not the limiting factors in the delayed proliferation. The induction of c-myc was retarded in the UDA group, and there was a good correlation between the kinetics of c-myc induction and the kinetics of cell proliferation. The comparison of the level of transcription of the genes encoding different cytokines revealed additional differences between the two mitogens: the whole wave of cytokine gene expression was delayed with UDA. In particular, IL2, IL3 and IFN gamma gene expression was retarded compared to the ConA-induced single wave. An even later transcriptional wave took place at around 72 h for IL4 and IL5. Finally, this particular kinetics corresponded to an unusually high level of IL3 and IFN gamma and a low level of IL4 and IL5 gene transcripts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Activated T lymphocytes from mice infected by lymphocytic choriomeningitis virus display high affinity IL-2 receptors but do not proliferate in response to IL-2.

The i.v. injection of mice with lymphocytic choriomeningitis virus (LCMV) initiates a rapid and long lasting immunodepression which can be monitored in vivo or in vitro. Splenic T lymphocytes taken from mice infected for 7 days with LCMV are characterized by a low proliferative capacity in response to Con A stimulation in vitro. In an initial attempt to understand the molecular mechanisms regulating the general anergy induced by the viral infection, we have analyzed the transcription of IL-2 and of p55 IL-2R alpha gene, two genes involved in T cell proliferation. IL-2 gene transcripts were hardly detected after Con A activation of spleen cells from LCMV-infected mice. In contrast, the expression of the gene encoding IL-2R alpha chain was induced as in control noninfected cells. In addition, the expression of the p75 IL-2R beta chain was not modified. The transcripts of the IL-2R alpha and of the IL-2R beta genes were normally translated as high affinity. IL-2R were expressed on the membrane of T lymphocytes from LCMV-infected mice. Despite the finding that these receptors could also internalize IL-2, the exogenous addition of this growth factor did not induce cell proliferation, indicating that the virus-induced blockade is multifocal.

Animals↗
PubMed1991

Interleukin 2/interleukin 4-independent T helper cell generation during an in vitro antigenic stimulation of mouse spleen cells in the presence of cyclosporin A.

Cyclosporin A (CsA), an immunosuppressive drug which completely suppresses the humoral response to thymus-dependent antigens, does not affect the generation of T helper (Th) cells during an in vitro stimulation of murine spleen cells with sheep red blood cells. The appearance of Th cells depends on time and their development can be prevented by X-ray irradiation performed at the onset of the culture and up to 3-4 days later; however, beyond this time, irradiation is ineffective, suggesting that cell proliferation is essentially completed by this time. The activity of Th cells generated in the presence of CsA is resistant to irradiation, indicating that the effector cells belong to a memory subset. Limiting dilution analysis has shown that the frequency of the Th cells recovered from 6-day sheep red blood cell-stimulated and CsA-treated cultures is of approximately 1.4 X 10(-3), representing an increment of about 500-fold compared to naive spleen cells. The increased frequency of Th cells and the sensitivity to irradiation of the generation of these cells demonstrate that Th cell precursors proliferate in the presence of CsA. Lymphokine genes transcription analysis confirms that the inhibition of interleukin (IL) 2/IL 4 gene expression is one target of CsA action. That the generation of Th memory cells can nevertheless take place strongly argues in favor of the existence of an IL 2/IL 4-independent pathway for murine T cell proliferation. Our finding that the transcription of the IL 7 gene is not inhibited by CsA raises the possibility for a role of this T cell growth factor in the generation of memory Th cells.

Animals↗
PubMed1990

Lymphocytic choriomeningitis virus-induced immunodepression: inherent defect of B and T lymphocytes.

Infection of mice with lymphocytic choriomeningitis virus (LCMV) produces a rapidly induced immuno-suppression manifested by low lymphocyte proliferation in response to lipopolysaccharide (LPS) and concanavalin A (ConA). Analysis of the mechanisms underlying the unresponsiveness to these mitogens was undertaken at the cellular and molecular levels 7 days after infection. The selective elimination of CD8+ T cells and the results of coculture experiments demonstrated that unresponsiveness was not due to suppressor cells. Similarly, the role of inhibitory factors such as prostaglandins was excluded, since indomethacin, which inhibits their production, did not reverse the unresponsiveness. Analysis of different cytokines secreted by ConA-activated macrophages or T cells revealed that interleukin-1 (IL-1), synthesized during the T-dependent activation of macrophages by ConA, was normally produced by cells from LCMV-infected mice. In contrast, IL-2, which is produced by activated CD4+ T cells, was undetectable. Addition of exogenous IL-2 did not restore the proliferative response, although the p55-kilodalton protein of the IL-2 receptor was induced by ConA on CD4+ cells from LCMV-infected mice. Our results can be interpreted as showing that (i) unresponsiveness to mitogens of cells from LCMV-infected mice is not due to altered functions of the macrophages with respect to IL-1 production; (ii) CD4+ cells are activated, since the p55 chain of the IL-2 receptor is induced; (iii) the lack of IL-2 production cannot explain T-cell unresponsiveness, since addition of exogenous IL-2 did not restore the proliferative response. Taken together, these data suggest that T-lymphocyte unresponsiveness should be related to an inherent proliferative defect subsequent to T-cell activation and IL-2 receptor expression.

Animals↗
PubMed1989

Functional heterogeneity of virgin and memory B murine lymphocytes revealed by the utilization of cyclosporin A: an overview.

The effects of cyclosporin A on the generation and revelation of B memory cells by thymus-independent (TI) antigens was investigated. A class 1 (TNP-LPS) and a class 2 (TNP-Ficoll) TI antigens were used for priming an elicitation. Evidence is presented that cyclosporin A does not interfere with the generation of hapten-specific (TNP) B memory cells by TNP-LPS or DNP-Ficoll. Cyclosporin A does not affect the revelation of B memory cells by TNP-LPS, but inhibits their revelation by TNP-Ficoll. These findings are discussed in terms of two distinct B cell lineages leading to antibody-forming cells and memory cells precursors, and in terms of heterogeneity of B memory cells.

Animals↗
PubMed1988

A sensitive, IL-2-independent, assay for IL-1.

The thymocyte costimulator (LAF) assay, the standard biological test used for IL-1 titration, has a low sensitivity and lacks specificity since it can be potentiated by the IL-2 which is frequently present in IL-1-containing biological fluids. We describe here a new IL-1 titration method which takes advantage of the capacity of a thymoma line, EL4-6.1, to differentiate and express IL-2 receptors upon stimulation by IL-1 in the presence of a suboptimal dose of phorbol diester. Membrane IL-2R measurement on this indicator cell line permits the detection of 1-2 X 10(-4) ng/ml IL-1, compared to 5 X 10(-2) ng/ml in the LAF assay. In addition, rIL-2 up to 250 U/ml has no effect on IL-1 measurement by this assay, which also exhibits a 100-fold lower sensitivity to inhibitory effects of prostaglandin, compared to the LAF assay. Finally, tumor necrosis factor alpha only exerts a weak costimulation effect at very high doses. A flow cytometry technique and an ELISA are described for IL-2 receptor detection. Due to its high sensitivity and specificity, this novel assay should now permit reliable IL-1 titration in biological fluids such as IL-2-rich lymphocyte culture supernatants.

Animals↗
PubMed1988

Secondary antibody responses to thymus-independent antigens. Decline and life-span of memory.

Immunological memory has been defined by the finding that upon a secondary injection of an antigen into an animal the immune response obtained differs from the response produced after the first inoculation of the antigen, independent of the length of time that can elapse between the first and second contact with antigen. In this report we have investigated the life-span of memory to a thymus-independent antigen, trinitrophenylated lipopolysaccharide (TNP-LPS), using a cell transfer system that allows the study of the function of isolated LPS-reactive "memory" B cells from C57BL/6 mice in histocompatible LPS-nonresponder C57BL/10ScCr hosts. We found that the longer the elapse of time between the transfer of TNP-LPS-primed C57BL/6 cells and the challenge of hosts with TNP-LPS, the lower the anti-TNP serum antibody level of the secondary response, i.e. in the absence of antigen, TNP-LPS memory cells have a short life-expectancy in the adoptive hosts as they do not persist for more than one or two weeks after transfer. Our present results suggest that induction and long-term persistence of memory to TNP-LPS in adoptive hosts cannot be solely explained by the long life-span of a subpopulation of antigen-specific memory B cells, but rather through the continuous recruitment of newly formed cells and probably antigen persistence.

Animals↗
PubMed1988

Urtica dioica agglutinin, a new mitogen for murine T lymphocytes: unaltered interleukin-1 production but late interleukin 2-mediated proliferation.

Urtica dioica agglutinin, a small-molecular-weight lectin purified from stinging nettle rhizomes, induces murine cell proliferation. U. dioica agglutinin is a specific T-cell mitogen for both thymocytes and spleen T lymphocytes; its mitogenic properties are strictly dependent on the presence of accessory cells. The kinetics of proliferation are markedly different from those of the classical T-cell mitogen concanavalin A, with a 2 to 3-day delay for both splenic and thymic populations and a rate of DNA synthesis twofold lower than that observed with concanavalin A. The late T-lymphocyte proliferation induced by U. dioica agglutinin correlates well with (i) the observed late interleukin-2 production and interleukin-2 receptor expression, and (ii) the long-lasting cyclosporin A-sensitive early activation period. In contrast, the production of interleukin-1 is not different, both in terms of concentration and kinetics, from that observed with concanavalin A.

Animals↗
PubMed1987

Cyclosporin A does not affect the in vitro induction of antigen-specific delayed-type hypersensitivity-mediating T cells.

The effect of cyclosporin A (CsA) on the in vitro induction of sheep red blood cell (SRBC)-specific T cells mediating the delayed-type hypersensitivity (DTH) reaction was studied. CsA (1 microgram/ml) addition to the culture medium totally inhibits the in vitro anti-SRBC humoral response but does not interfere with the generation of anti-SRBC DTH-mediating T (TDTH) cells. The induction of TDTH requires the presence of antigen and their expression is mediated selectively by the antigen used in the culture. The TDTH cells generated are Lyt-1+,2- and their induction occurs with a similar efficiency in CsA-treated and untreated cultures: the frequency of the TDTH cells increases by a factor of 10 to 20 during the 6-day incubation period. Lyt-2+ suppressor cells are also generated in CsA-treated or untreated cultures. Our results suggest that a small fraction of T cells can be driven into the proliferative pathway by antigen even in presence of CsA.

Animals↗
PubMed1987

Hybrid polypeptide heavy chains produced by two hybridoma lines.

Two anti-TNP antibodies exhibiting unusual features are described. They were obtained in two independent fusions. Spleen cells from CB20 mice sensitized with TNP-Ficoll and challenged with TNP-LPS were fused with SP2/0 myeloma cells. One of these hybridomas, CBT3, secretes antibodies which react with both monospecific anti-gamma 2b and anti-gamma 3 anti-isotypic sera; the second hybridoma, CBT4, secretes antibodies reacting with monospecific anti-mu and anti-gamma 2b sera. Only one type of immunoglobulin is secreted by each hybridoma, ruling out the hypothesis of hybrid molecules formed by distinct heavy chains. These results imply that the two heavy chains are made up from elements encoded by gamma 3 and gamma 2b genes in CBT3 and by gamma 2b and mu genes in CBT4. The molecular mechanisms underlying the production of these singular heavy chains are discussed.

Animals↗
PubMed1986

The expression of the sIgD isotype in wild-derived mice.

IgD and IgM are concomitantly expressed on the surface of most mouse B lymphocytes and both molecules serve as receptor for antigen. In this communication we report that in contrast to IgM, which is expressed in a constant manner on the surface of spleen B lymphocytes of different laboratory and wild-derived mice, IgD expression is variable among the spleen cells of wild-derived mice. SPE, SEI, and SFM mice belonging to the Mus 3 subgroup show a fluorescence profile characterized by a marked diminution in the population of B lymphocytes expressing the IgD isotype; in addition, these cells have a low sIgD density on their membranes. These findings were confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the iodinated membrane proteins. Polyclonal in vitro activation with lipopolysaccharide increases the frequency of surface IgD (sIgD)-bearing spleen cells and sIgD density in the SPE strain but decreases both the frequency and the density of IgD bearing cells in the BALB/c strain. This result suggests that delta gene expression is regulated differently in SPE and BALB/c mice. In addition, genetic analysis of sIgD expression in (BALB/c X SPE)F1 hybrids suggests that the proportion of sIgD-bearing cells and sIgD density are independently regulated.

Animal Population Groups↗