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Biomedical subjects

S Chouaib

Publications and source records attributed to S Chouaib.

At least 109 records · Page 6Linked to original sources
PubMed1989

[Tumor necrosis factor alpha (cachectin). Biological properties and role in physiopathology].

Cachectin, or TNF-alpha (tumor necrosis factor alpha) was first described as a product of activated monocytes capable of inducing tumor cell lysis both in vitro and in vivo. In addition to this activity, TNF-alpha has been shown to possess many other biological properties: it modulates the synthesis of the enzymes involved in lipogenesis and regulates the function of various types of normal cells, such as fibroblasts, osteoblasts, endothelial cells and adipocytes. Moreover, TNF-alpha - displays multifunctional immunoregulatory activity on T and B lymphocytes and on natural killer and lymphokine activated killer cells and plays a major role in the defence against infections and in the immune response against cancer. In severe infection or cancer, an excessive production of TNF-alpha may be responsible for septic shocks or cachexia in both animals and man. The high conservation of the TNF-alpha gene in all species despite its toxicity indicates that it plays a crucial but still partially understood role.

Animals↗
PubMed1988

Allogeneic T cell activation triggering by MHC class I antigens.

The role of MHC-encoded class I molecules in allogeneic activation and proliferation of human T lymphocytes was investigated. The study was performed by using primary mixed culture of lymphocytes from MHC recombinant siblings identical for MHC class II Ag (DR, DP, DQ) and displaying MHC class I disparity. The results indicate that such allogeneic combination is sufficient to trigger early activation steps within responder T cells without promoting a significant proliferation. After MHC class I allosensitization, a significant proportion of cells entered the cell cycle (G0----G1). The stimulatory potential of MHC class I Ag was further stressed by the specific induction on responder cells of IL-2R (22% T cell activation Ag positive). Under the same experimental conditions, transferrin receptor expression and IL-2 activity were not detectable. This is consistent with the low T cell proliferation. Exogenous rIL-1 did not improve IL-2 production and the subsequent T cell proliferation indicating that these two events were not associated with a defective accessory cell function involving IL-1 release. MHC class I disparity can also prime precursor CTL to differentiate into IL-2-dependent functional MHC restricted cytotoxic T cells. Conversely IFN-gamma had no effect. Addition to the culture of W6/32, a mAb specifically directed against a monomorphic determinant on human class I HLA-A, -B, and -C Ag was able to block all these activation events. These data clearly indicate a role of HLA class I Ag involvement in the early events triggering allogeneic T cell activation.

Antibodies, Monoclonal↗
PubMed1988

Generation of lymphokine-activated killer cells: synergy between tumor necrosis factor and interleukin 2.

Large granular lymphocytes (LGL) can be activated by interleukin 2 (IL-2) to lymphokine-activated killers (LAK). The effect of tumor necrosis factor (TNF) on LAK generation was investigated. TNF was found to act synergistically with low concentrations of IL-2 (0.10-0.25 ng/ml), which were ineffective by themselves in inducing LAK activity, to promote the differentiation of LGL into non-major histocompatibility complex-restricted killers. When IL-2 was used at concentrations optimal for LAK generation, TNF did not further enhance this phenomenon. Specific binding of 125I-labeled TNF to LGL was increased by IL-2 stimulation. Scatchard analysis of TNF binding revealed the existence of two classes of binding sites with markedly different affinities (Kd values of 57 and 600 pM). We also demonstrated that the IL-2/TNF synergistic induction of LAK activity did not involve either IL-1 or interferon-gamma. This IL-2/TNF synergistic effect was blocked by anti-Tac antibodies. Immunofluorescence analysis revealed that IL-2/TNF selectively up-regulated Tac antigen expression on LAK precursors. Our results suggest a functional interaction between IL-2 and TNF on LAK precursors, which results in a reduction of the IL-2 concentration required for differentiation of LGL into LAK killers.

Drug Synergism↗
PubMed1988

Expression of the T cell gamma gene by a functionally defined human T cell clone. Characterization at DNA, RNA, and cell membrane level.

In the present study we describe one CD2+CD3+ clone termed DS6 which expressed neither CD4 nor CD8 differentiation antigens and failed to react with WT31, a monoclonal antibody directed against the T cell antigen receptor alpha/beta heterodimer. This clone was isolated from peripheral blood T lymphocytes of a patient with a prolonged immunodeficiency after allogeneic bone marrow transplantation. Normal-sized T cell gamma gene transcripts were detected in DS6 by northern analysis, whereas no mature beta or alpha chain mRNA were found. The rearrangement of TCR beta chain genes and T cell gamma genes was analysed. While in DS6, TCR beta chain genes remain in germinal configuration, and a unique pattern of monoallelic T cell gamma gene rearrangement was observed. The rearrangement involves the recently described V gamma 5 segment and the J gamma 1 joining segment, which is located upstream of the C gamma 1 constant region. To determine the molecular structure present on DS6, an immunoprecipitation was performed with monoclonal anti-CD3 antibody and a rabbit antiserum raised against gamma protein. We have observed, in association with the CD3 complex, a 90 kDa structure which under reducing conditions resolves into three subunits of 45, 40 and 37 kDa. We demonstrated that the rabbit anti-gamma serum only immunoprecipitates the two lower bands. The upper band corresponds to a presently undefined T cell receptor chain. Next, we showed the non major histocompatibility complex (MHC)-restricted cytolytic activity exhibited by these CD3+CD4-CD8- cloned T cells and inhibition of the natural killer (NK)-like activity by the anti-CD3 monoclonal antibody. The triggering of CD2 or CD3 molecules increased IL-2 receptor expression on DS6 but failed to induce cell proliferation. This contrasts with recent results obtained with gamma-expressing T cell clones and illustrates the functional heterogeneity of the cells bearing the second T cell receptor.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1988

[Functional interaction between the tumor necrosis factor and interleukin 2 during induction of lymphokine activated killer cytotoxic activity].

TNF has a differential effect on the induction of LAK activity which is dependent on the IL-2 concentrations used for LGL stimulation. TNF was found to synergize with low concentrations of IL-2 which are normally ineffective in inducing LAK activity. When IL-2 was used at concentrations optimal for LAK generation, TNF did not further enhance the differentiation of LGL into LAK effectors. When anti-TNF was included in the 51Cr-release assay, no effect on the cytolytic activity was observed. We also demonstrate that IL-2 induced an increase of specific TNF binding to LGL.

Dose-Response Relationship, Drug↗
PubMed1987

Analysis of prostaglandin E2 effect on T lymphocyte activation. Abrogation of prostaglandin E2 inhibitory effect by the tumor promotor 12.0 tetradecanoyl phorbol-13 acetate.

We have investigated the inhibitory potential of prostaglandin E2 (PGE2) with respect to intracellular messengers implicated in the signaling system of T-lymphocyte activation pathway. Using the fluorescent indicator Quin 2, it is demonstrated that PGE2 inhibits the increase in cytosolic-free calcium concentration [Ca2+]i. Reconstitution of calcium mobilization in the presence of PGE2 by the calcium ionophore A23187 results in a partial restoration of both interleukin 2 (IL2) production and cell proliferation and has no effect on the inhibition of transferrin receptor expression. In contrast, the treatment of cell cultures with the tumor promotor 12.0 tetra decanoyl phorbol-13-acetate (TPA) abrogates the suppressor activity of PGE2. When T lymphocyte stimulation is provided by the combination of A23187 and TPA, the PGE2 inhibitory effect does not occur. These data also indicate that the down regulation of transferrin receptor by PGE2 is proximal to protein kinase C activation and is not associated with decreased expression of the functional IL2 receptor.

Calcimycin↗
PubMed1986

A common pathway for T lymphocyte activation involving both the CD3-Ti complex and CD2 sheep erythrocyte receptor determinants.

T lymphocyte activation with monoclonal antibodies directed against the CD2 (T,p50) sheep red blood cell receptor antigen and against CD3 (T,p19,29) has been investigated. Co-stimulation of purified T lymphocytes with anti-CD3 (SP34) and anti-CD2 (9-1), which detects a unique epitope on the CD2 molecule, results in T cell activation and cell proliferation. Each antibody alone is unable to mediate this effect. Co-stimulation of purified T cells with two different anti-CD2 antibodies, 9-1 and 9.6, which detect two different epitopes on the CD2 molecule, are also mitogenic. In contrast, the combination of anti-CD3 (SP34) and anti-CD2 (9.6) cannot induce T cell activation. These data suggest that the CD2 epitope defined by the 9-1 antibody is functionally important for T cell activation via the CD3/Ti complex. Furthermore, it is demonstrated that anti-CD3 (SP34) induces epitopic modulation of the CD2 molecule, resulting in enhanced expression of the CD2, 9-1 epitope. This epitope modulation of the CD2 (9-1) epitope by anti-CD3 (SP34) occurs instantaneously at 4 degrees C and in the presence of NaN3. The functional interaction between CD3 and CD2 occurs in spite of any evidence of complex formation between these two molecules. These data suggest that the T cell differentiation antigens CD3 and CD2 are jointly involved in antigen-specific T cell activation. The data are consistent with a model for antigen-specific T cell activation involving both the CD3/Ti complex and subsequent activation of the CD2 complex T cell activation by co-stimulation with anti-CD3 (SP34) and anti-CD2 (9-1) is substantially enhanced by the addition of exogenous, purified interleukin 1 (IL 1). These data would suggest that the CD2 complex, as well as the putative IL 1 receptor, are involved in separate and complementary receptor-ligand interactions, resulting in the amplification of antigen-specific T cell responses.

Animals↗
PubMed1986

[Production of IL2 and induction of IL2 receptor: two independent and dissociable events during allogenic stimulation in vitro in man].

Donors from HLA genotyped families are extremely useful for immunogenetic studies. Analysis of the in vitro allogenic response of lymphocytes from HLA recombinant siblings can dissect the respective role of HLA class I and class II antigens for the lymphocyte activation. Using lymphocytes from such donors, we have demonstrated that IL2 production is triggered by HLA class II disparities (but not by HLA class I), HLA class I disparities can prime the cytotoxic T lymphocytes precursors inducing the IL2 receptor on the specific clones which will proliferate in presence of IL2 either from endogenous origin (in the case of HLA class II disparities) or from experimentally added IL2 in the culture.

Cytotoxicity, Immunologic↗
PubMed1985

Prostaglandin E2 acts at two distinct pathways of T lymphocyte activation: inhibition of interleukin 2 production and down-regulation of transferrin receptor expression.

The mechanism by which prostaglandin E2 (PGE2) inhibits human T lymphocyte activation and proliferation was studied. We analyzed the effect of physiologic concentrations of PGE2 on interleukin 2 (IL 2) production, expression of IL 2 receptor (Tac antigen), and expression of the transferrin receptor after in vitro activation with phytohemagglutinin. PGE2 inhibited T lymphocyte proliferation by 80 to 90% of control values. This was associated with a similar degree of inhibition of IL 2 production while the expression of IL 2 receptor was not affected. This was in marked contrast to the expression of the transferrin receptor, which was inhibited 65% after 72 hr of in vitro activation. The addition of exogenous, purified IL 2 reconstituted lymphocyte proliferation to 50% of control values, but had no effect on transferrin receptor expression. Because PGE2 is known to increase the intracellular concentration of 3',5' cyclic adenosine monophosphate (cAMP), we investigated the effect of another adenylate cyclase activator, i.e., isoproterenol, as well as the effect of extracellular administration of the cAMP derivative dibutyryl cAMP (dBcAMP) on IL 2 production, Tac antigen expression, and transferrin receptor expression. It was demonstrated that isoproterenol, as well as dBcAMP, inhibited transferrin receptor expression on PHA-activated T lymphocytes to the same extent as PGE2, and exogenous IL 2 could not counteract the down-regulation of the receptor expression. In contrast, neither isoproterenol nor dBcAMP had any significant effect on IL 2 receptor expression. Prostaglandin F2 alpha (PGF2 alpha), which has been reported to elevate intracellular cyclic GMP levels, had no effect on lymphocyte activation and proliferation, and did not counteract the PGE2-induced depression in IL 2 production. In contrast to its effect on peripheral blood lymphocytes, PGE2 had no effect on transferrin receptor expression or cell proliferation by IL 2-dependent T cell clones and IL 2-independent T cell lines. These studies demonstrate that PGE2 exerts its inhibitory effects on T cell activation and proliferation via two distinct pathways: inhibition of IL 2 production and inhibition of transferrin receptor expression. The transferrin receptor inhibition is mediated via the cAMP pathway and is IL 2-independent.

Antigens, Surface↗
PubMed1985

Differential effect of anti-beta 2-microglobulin on IL 2 production and IL 2 receptor expression in the primary mixed lymphocyte culture reaction.

The mechanism of inhibition of the proliferative response in primary mixed lymphocyte culture (1 degree MLC) by antibodies to beta 2-microglobulin (beta 2m) was investigated. It is demonstrated that anti-beta 2m antibodies inhibit the production of interleukin 2 (IL 2). In contrast, the expression of IL 2 receptor is not affected by anti-beta 2m. The addition of purified exogenous IL 2 to the antibody-treated 1 degree MLC can completely restore the proliferative response, indicating that anti-beta 2m does not interfere with IL 2 binding to its receptor. Similarly, anti-beta 2m does not interfere with the capacity of IL 2-dependent T cell lines or T cell clones to respond to exogenous IL 2. The inhibition of cell proliferation and IL 2 production by anti-beta 2m is maximal when the antibody is added at the beginning of 1 degree MLC culture, and no effect of anti-beta 2m is seen when added after 3 days of culture. Anti-beta 2m has no effect on mitogen-induced cell proliferation and IL 2 production. Anti-beta 2m acts on the responder cell population, as demonstrated in experiments in which responder cells or stimulator cells are treated separately with the antibody. The expression of HLA-class II antigens (i.e., HLA-DR and DQ (DC) on the T cells activated on 1 degree MLC is not affected by anti-beta 2m. These studies indicate that the HLA-beta 2m class I antigen complex plays a role in T lymphocyte activation via release of IL 2, and suggest the existence of different mechanisms for activation of IL 2 producers and IL 2 responders in 1 degree MLC.

Antibodies, Monoclonal↗
PubMed1985

[Abnormal regulation in the production of IL2 in Hodgkin's disease].

Patients with active Hodgkin's disease demonstrate a significant depression of cellular immunity. The present study, performed with lymphocytes from 16 untreated patients with active Hodgkin's disease and 13 healthy control volunteers, demonstrate an equivalent IL 2 production in vitro in both groups. Our results, however, demonstrate an abnormal regulation of IL 2 production in patients. A negative control of IL 2 production involving monocytes producing PGE 2 able to induce radiosensitive suppressor T lymphocytes, has been identified previously with cells from healthy donors. In the present study we demonstrate that this negative control is hyper functioning with cells from Hodgkin's disease patients.

Hodgkin Disease↗
PubMed1984

The mechanisms of inhibition of human IL 2 production. II. PGE2 induction of suppressor T lymphocytes.

In vitro and in vivo experiments indicate that the production of interleukin 2 (IL 2) by T lymphocytes is critical for the development of the effector phase of immunity. Complex cellular interactions are involved for the induction of IL 2 production. We have shown in a previous study that in humans monocytes can transmit opposite signals to the IL 2-producing cells. In addition to the positive signal delivered through the release of interleukin 1, human monocytes can deliver a negative signal through the release of prostaglandin E2 (PGE2). This monokine, known to activate suppressor mechanisms in several systems, was shown to inhibit IL 2 production. The data presented in this paper show that this PGE2-dependent inhibition is strictly dependent upon the presence of radiosensitive T cells in the culture, suggesting that PGE2 induces the activation of suppressor T cells modulating IL 2 production. Kinetics experiments indicate that these suppressor cells are radiosensitive during their induction phase but become radioresistant after 18 hr of incubation in the presence of PGE2. Successful in vitro induction of suppressor cells by incubation of enriched T cells with PGE2 was decisive for the analysis of the phenomenon. The induced suppressors were capable of inhibiting IL 2 production by fresh autologous T cells as well as inhibiting PHA proliferative response by these cells. A quantitative evaluation of IL 2 receptors on PGE2-treated cells has indicated that this absorption capacity was similar to the capacity of PBL known to express a low number of IL 2 receptors, thus excluding a suppression via absorption or competition for IL 2. No detectable killing of IL 2-producing cells by PGE2-induced suppressors was observed. The OKT4 and OKT8 phenotype of suppressor cells was examined. T cells were purified at two stages of differentiation before or after induction by PGE2 in vitro treatment. We conclude from these experiments that PGE2 activates suppressor cells among precursors segregating predominantly with the OKT8 subset and fewer cells with the OKT4 subset. After differentiation, however, the suppressor cells segregate with the OKT8 subset only. Such results were obtained by using positive selection (cellular affinity columns) and negative selection (monoclonal antibodies plus complement).

Absorption↗
PubMed1983

Improved culture conditions for quantitative evaluation of interleukin 2 production by frozen human lymphocytes.

Several culture parameters were studied in order to establish methods for optimal and reproducible production of interleukin 2 (IL2) by thawed lymphocytes. Standard conditions, considered optimal for production by freshly separated lymphocytes (culture medium RPMI 1640 + 1% normal human serum + 10 micrograms/ml PHA), gave low and poorly reproducible results. An increased concentration of human serum (10 and 20%) in the medium improved production but best results were obtained by adding polyethylene glycol (PEG 6000, 0.1 mg/ml) to the culture medium. Furthermore, with the addition of PEG 6000, results became highly reproducible, thus permitting valid comparison of in vitro IL2 production by lymphocytes from normal donors and patients.

Blood↗
PubMed1982

[Cellular regulation of human interleukin-2 production].

The mechanism of IL2 production by T lymphocytes has been clearly established in Mice. Previous studies have also suggested that control of IL2 production is similar in the Human. We have observed that a complete depletion of adherent monocytes abrogates IL2 production by T lymphocytes. On the other hands in humane inhibition of IL2 production was also mediated by an excess of monocytes. This inhibition was mediated by soluble products and could be blocked by treatment with indomethacin. PGE2 was identified as one of this, inhibitory monokine. A possible mechanism of this inhibition by PGE2 is suggested. Such inhibition was not observed if the T lymphocyte suspension was irradiated (1000 rad) before addition of PGE2 or excess monocytes. These results suggest that activation of a radiosensitive T cell by monokines is required for the inhibition of IL2 production. A model for the cellular control of human IL2 production is proposed.

Cell Adhesion↗
PubMedDate not supplied

Modulation of TNF-mediated cell lysis in vitro: further analysis of intracellular signaling.

We have investigated the post-receptor events governing the Tumor Necrosis Factor (TNF)-mediated cytotoxicity in vitro. As calcium has been reported to be an essential mediator in the cell killing processes, we asked whether an early increase in intracellular calcium could be involved during TNF-induced cell death. Using the ACAS methodology (adherent cell analysis and sorting), we could not detect any significant increase in intracellular calcium following TNF treatment (40 s) within the TNF-sensitive human breast carcinoma MCF7 cell line. In addition, A23187 (0.1-0.4 microM) did neither enhance TNF-mediated MCF7 cell lysis, further confirming that TNF-mediated cell lysis can occur in the absence of an early calcium increase. Given the potentiating effect of cAMP-inducing agents, such as forskolin, on TNF-mediated cytotoxicity, we have investigated the relationship between cAMP accumulation and the TNF signaling pathway during cell death. Our results indicate that the potentiating effect of forskolin (50 microM) on TNF-mediated MCF7 cell lysis did not involve a modulation in the TNF-induced activation of the nuclear factor NF-kB but was associated with an increase in the DNA fragmenting capacity of TNF as assessed by agarose gel electrophoresis of target cell DNA.

Adenocarcinoma↗