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Biomedical subjects

D Olive

Publications and source records attributed to D Olive.

At least 109 records · Page 6Linked to original sources
PubMed1996

Differential recognition by CD28 of its cognate counter receptors CD80 (B7.1) and B70 (B7.2): analysis by site directed mutagenesis.

CD28, which is a member of the immunoglobulin superfamily of molecules (IgSF), is a homodimer of two polypeptides containing a single V-like domain with short transmembrane and cytoplasmic regions. It serves as a co-signalling molecule for T cell activation through binding to its cognate counter-receptors CD80 and B70, expressed on antigen presenting cells. In the current study, we investigated the regions of CD28 which are involved in its interactions with CD80 and B70, using site directed mutagenesis, CD28 mAb epitope mapping, receptor based adhesion assays and direct binding of Ig-fusion proteins to cell surface receptors. Truncation or substitution of a stretch of a proline rich "hallmark" sequence, "MYPPPY", abrogates binding to CD80 or B70, while retaining CD28 mAb epitopes and cell surface expression. On an Ig-fold model of the CD28 V-domain, this fully conserved motif localizes to a CDR3-like region. Mutations introduced into other loops, including the CDRI-like and CDR2-like regions, had very little effect on CD80 or B70 binding. Mutations introduced within the predicted beta-strand regions caused loss of receptor expression. Conservative substitution of both the flanking tyrosine residues within the "MYPPPY" motif with phenylalanine, caused loss of binding to B70 but not to CD80. These results show that, although the same overall region on CD28 may be involved in the interactions with CD80 and B70, subtle but important differences distinguish recognition by the two molecules. These finding, along with previous observations on the differential pattern of expression and tissue distribution of CD80 and B70, support the contention that these molecules play distinct roles in the regulation of immune responses in vivo.

Abatacept↗
PubMed1996

CD28 signal transduction pathways. A comparison of B7-1 and B7-2 regulation of the map kinases: ERK2 and Jun kinases.

The present study compares the mitogen-activated protein (MAP) kinase responses in T cells activated with the CD28 ligands B7-1 (CD80) and B7-2/B70 (CD86). Ligands B7-1 and B7-2 do not activate the Raf-1/ERK2 cascade, but share the ability to activate related Jun kinases. These natural ligands for CD28 had no stimulatory effect alone on Jun kinase activation, but the data show that B7-1 and B7-2 could both co-operate with intracellular Ca2+ increase and protein kinase C (PKC) activation to stimulate Jun kinases. The present study shows that the interaction of CD28 with its ligands B7-1 and B7-2 can induce identical signal transduction through the MAP kinase cascades.

Antigens, CD↗
PubMed1996

Predominant involvement of CD8+CD28- lymphocytes in human immunodeficiency virus-specific cytotoxic activity.

Distinct functional CD8+ T-cell populations have been observed during human immunodeficiency virus (HIV) infection. One of these functions is the inhibition of viral replication by a noncytotoxic mechanism, which was shown to be mediated by the CD8+CD28+ subpopulation. On the other hand, CD8+ T cells exert an HIV-specific cytotoxic activity. The present study shows that CD8+CD28- lymphocytes display this HIV-specific cytotoxic activity, which is detectable immediately after the cells are purified from peripheral blood. The CD28- population is also able to proliferate and to retain its cytotoxic activity after in vitro restimulation with autologous blast cells. Finally, HIV-specific cytotoxic T cells can be obtained in vitro from the CD8+CD28+ population.

CD28 Antigens↗
PubMed1995

In vivo regulation of interleukin-2 receptor alpha gene transcription by the coordinated binding of constitutive and inducible factors in human primary T cells.

IL-2R alpha transcription is developmentally restricted to T cells and physiologically dependent on specific stimuli such as antigen recognition. To analyse the mechanisms used to activate IL-2R alpha transcription as well as those used to block it in non-expressing cells, we determined the protein-DNA interactions at the IL-2R alpha locus in three different cell types using the DMS/LMPCR genomic footprinting method. CD25/IL-2R alpha can be efficiently induced in primary human T cells since approximately 100% express this gene when receiving an appropriate combination of mitogenic stimuli. To understand why IL-2R alpha is not expressed in other haematopoietic cell types, we analysed BJAB B lymphoma cells which do not express the IL-2R alpha gene and contain constitutively active nuclear NF-kappa B. Primary fibroblasts from embryo and adult skin were selected to examine the mechanisms that may be used to keep the IL-2R alpha gene inactive in non-haematopoietic cells. The three main results are: (i) the stable in vivo occupancy of IL-2R alpha kappa B element in resting T cells, most probably by constitutive NF-kappa B p50 homodimer that could impair SRF binding to the flanking SRE/CArG box; (ii) its inducible occupancy by NF-kappa B p50-p65 associated with the binding of an SRE/CArG box DNA-binding factor upon mitogenic stimulation; and (iii) a correlation between the precommitment of T cells to activation and the presence of stable preassembled protein-DNA complexes in contrast with the bare IL-2R alpha locus in non-T cells.

Antineoplastic Agents↗
PubMed1995

Impairment of leukaemia-free survival by addition of interleukin-2-receptor antibody to standard graft-versus-host prophylaxis.

Graft-versus-host disease (GVHD) is the most important adverse effect of HLA-matched allogeneic bone-marrow transplantation. T-cell depletion of the graft eliminates GVHD but also causes an unacceptable increase in rejections and leukaemic relapses. We have attempted to block the activation of resting T cells with a monoclonal antibody against the interleukin-2 receptor (33B3.1). 101 patients with leukaemia (acute lymphocytic 22, acute myelogenous 34, chronic myeloid 45) in first complete remission or first chronic phase were randomly assigned to groups receiving standard post-transplantation immunosuppression (methotrexate plus cyclosporin; n = 50) or the standard treatment plus antibody 33B3.1 (n = 51). There were 2 graft failures in the 33B3.1 group. The antibody did not significantly affect the cumulative frequency of acute GVHD of grade 2 or worse (19 [38%] vs 23 [46%]) but merely delayed its onset (median 36 [IQR 21-70] vs 25 [11-44] days; p < 0.01). At median follow-up of 58 (range 41-71) months, the antibody-treated group had significantly lower leukaemia-free survival (p < 0.05) mainly because of a progressive increase in the rate of late relapses (p = 0.08). Our findings confirm the importance of T cells in transplantation for leukaemia. The fine balance between the early modulation of transplant immunity and leukaemic control suggests that further anti-leukaemic measures may be needed when attempts are made to improve tolerance between the graft and the leukaemic host.

Adolescent↗
PubMed1995

CD28 costimulation up-regulates long-term IL-2R beta expression in human T cells through combined transcriptional and post-transcriptional regulation.

Costimulatory molecules such as CD28 are required for induction of T cell clonal expansion and for prevention of T cell unresponsiveness. In combination with either CD3 or CD2 triggering, CD28 was shown to enhance T cell proliferation, cytolytic activity, production of cytokines and especially of IL-2, and expression of the IL-2R alpha-chain (IL-2R alpha). We and others have demonstrated that the costimulatory effect of CD28 on both IL-2 and IL-2R alpha expression results from a coordinated transcriptional activation of their genes and transcript stabilization. We show here that the CD28 stimulation, together with CD2, leads to a prolonged up-regulation of the constitutive expression of the IL-2R beta-chain in human peripheral T cells. As for IL-2R alpha, the increase in IL-2R beta gene expression seems to result from both transcriptional activation and transcript stabilization. In addition, IL-2 differentially regulates its own receptors, as only expression of IL-2R alpha, but not of IL-2R beta, is largely inhibited, at both the mRNA and protein levels, by blocking IL-2R mAbs. We propose that the long lasting T cell proliferation mediated by the CD2 and CD28 costimulation is mainly the consequence of the high and prolonged expression of both the IL-2R alpha- and beta-chains.

Blotting, Northern↗
PubMed1995

Preovulatory sonographic uterine receptivity index (SURI): usefulness as an indicator of pregnancy in women undergoing assisted reproductive treatments.

To evaluate the uterine component as a determinant variable in the probability of establishing a pregnancy after assisted reproductive treatments, we introduced a mathematical formula derived from standard endovaginal uterine monitored color Doppler imaging parameters. We analyzed 102 cycles of ovarian stimulation with leuprolide acetate and exogenous gonadotropins resulting in 52 clinical pregnancies by stepwise logistic regression analysis. Sonographic endometrial pattern, thickness, diastolic blood flow, and resistive index variables were transformed into categorical variables and forced to yield a regression equation. Sonographic uterine receptivity index was calculated as a summation of four times endometrial pattern, five times resistive index, and two times diastolic blood flow. This index yielded values for each patient in a range of 0 to 15. Scores > or = 13 were associated with a successful outcome in 79.4% of the patients, whereas scores between 8 and 12 were accompanied by 45.8% pregnancy rates (P = 0.01), and scores < or = 7 had successful treatment outcome in only 7.7% (P = 0.0001). The scores obtained by this mathematical equation provide the ability to make reliable predictions about the outcome of assisted reproductive treatments in women undergoing ovulation induction with leuprolide acetate and human menopausal gonadotropins.

Adult↗
PubMed1994

The role of p21ras in CD28 signal transduction: triggering of CD28 with antibodies, but not the ligand B7-1, activates p21ras.

CD28 is a 44-kD homodimer expressed on the surface of the majority of human T cells that provides an important costimulus for T cell activation. The biochemical basis of the CD28 accessory signals is poorly understood. Triggering of the T cell antigen receptor (TCR) activates the p21ras proteins. Here we show that ligation of CD28 by a monoclonal antibody (mAb) also stimulates p21ras and induces Ras-dependent events such as stimulation of the microtubule-associated protein (MAP) kinase ERK2 and hyperphosphorylation of Raf-1. One physiological ligand for CD28 is the molecule B7-1. In contrast to the effect of CD28 mAb, the present studies show that interactions between CD28 and B7-1 do not stimulate p21ras signaling pathways. Two substrates for TCR-regulated protein tyrosine kinases (PTKs) have been implicated in p21ras activation in T cells: p95vav and a 36-kD protein that associates with a complex of Grb2 and the Ras exchange protein Sos. Triggering CD28 with both antibodies and B7-1 activates cellular PTKs, and we have exploited the differences between antibodies and B7-1 for p21ras activation in an attempt to identify critical PTK-controlled events for Ras activation in T cells. The data show that antibodies against TCR or CD28 induce tyrosine phosphorylation of both Vav and p36. B7-1 also induces Vav tyrosine phosphorylation but has no apparent effect on tyrosine phosphorylation of the Grb2-associated p36 protein. The intensity of the Vav tyrosine phosphorylation is greater in B7-1 than in TCR-stimulated cells. Moreover the kinetics of Vav tyrosine phosphorylation is prolonged in the B7-1-stimulated cells. These studies show that for CD28 signaling, the activation of p21ras correlates more closely with p36 tyrosine phosphorylation than with Vav tyrosine phosphorylation. However, the experiments demonstrate that Vav is a major substrate for B7-activated PTKs and hence could be important in CD28 signal transduction pathway.

Adaptor Proteins, Signal Transducing↗
PubMed1994

Binding of phosphatidylinositol-3-OH kinase to CD28 is required for T-cell signalling.

The engagement of CD28 with its ligand B7.1/CD80 results in potent costimulation of T-cell activation initiated through the CD3/T-cell receptor complex. The biochemical basis of CD28 costimulatory function is poorly understood. The signalling pathways used by CD28 are unlike those used by the CD3/T-cell receptor in that they are resistant to cyclosporin A and independent of changes in cyclic AMP concentrations. These differences suggest that each pathway provides unique biochemical information which is required for T-cell activation. We report here that CD28 becomes tyrosine-phosphorylated following interaction with B7.1/CD80, which induces formation of a complex with phosphatidylinositol-3-OH kinase, mediated by the SH2 domains of the p85 subunit of the kinase. Phosphatidylinositol-3-OH kinase is a heterodimer of this 85K regulatory subunit and a 110K catalytic subunit, and is a common substrate for most receptor tyrosine kinases and some cytokine receptors, binding through its SH2 domain to phosphotyrosine in the motif Tyr-X-X-Met in the CD28 sequence, which is highly conserved between human, mouse and rat and lies in the intracellular domain. We show that CD28 mutants that have their kinase-binding site deleted or the tyrosine at position 173 substituted by phenylalanine do not associate with the kinase after CD28 stimulation and cannot stimulate production of interleukin-2. Our results suggest that phosphatidylinositol-3-OH kinase is critical for signalling by CD28.

Animals↗
PubMed1994

Regions of the CD8 molecule involved in the regulation of CD2-mediated activation.

The CD8 molecule regulates T cell activation mediated via the CD3 T cell receptor and the adhesion molecule CD2. CD8 mAbs have been found to inhibit early (Ca2+ rise) as well as late events (cytotoxicity, proliferation, and lymphokine secretion) mediated via the CD2 pathway. A panel of eight anti-human CD8 mAbs was tested for inhibition of CD2-mediated Ca2+ rise in a cytotoxic T cell clone. The inhibition ranged from 5 to 53% independently of mAb isotype and affinity measured by half saturation binding. We then characterized these mAbs for their reactivity toward three mutants of the human CD8 alpha carrying amino acid sequence changes in the surface-exposed loops homologous to the immunoglobulin CDR1, 2, and 3. The mutations included replacement of the human CD8 alpha CDR1- and CDR2-like loops by the homologous mouse sequences and the insertion of a glycine in the middle of the CDR3-like loop. Thus, five mAbs were found to be affected by the mutation in the CDR2-like loop but not by alterations in the other CDR-like loops. Conversely, the other two mAbs (8E1.7 and B9.8) were affected only by mutations in the CDR1- and CDR3-like loops, respectively. Cross-inhibition experiments were essentially in agreement with these results. Interestingly, all the mAbs directed against the CDR2-like loop were potent inhibitors of CD2-mediated Ca2+ rise, with one exception probably due to poor affinity. Thus, in addition to being a site of interaction with major histocompatibility complex Class I as recent data have indicated, this region of the CD8 alpha subunit may play a role in regulating T cell activation.

Antibodies, Monoclonal↗
PubMed1994

Profound and possibly primary "idiopathic CD4+ T lymphocytopenia" in a patient with fungal infections.

A profound and long-lasting reduction in circulating CD4+ T lymphocytes (< 80/microliters) was found in a 37-year-old man (without known risk factors for HIV infection) presenting with recurrent oral candidiasis who subsequently developed cryptococcal meningitis. Infection with HIV was ruled out by serological and virological studies. In vitro and in vivo cell-mediated immunity was severely impaired. Abnormal phenotypic patterns of both CD4+ and CD8+ cells were consistently observed. A systematic family survey revealed in some of his asymptomatic relatives several immunological abnormalities which may point to a genetically based primary immunodeficiency disorder.

Adult↗
PubMed1994

Functional expression of human CD28 in murine T cell hybridomas.

CD28 is a 44 kDa Ig superfamily cell surface molecule expressed on most mature T cells. Through its interaction with the recently identified B7/BB1 counter-receptor, it is believed to play an important role as a co-stimulator of T cells along with the TCR-CD3 complex. Activation of T cells with CD28 mAbs synergizes with TCR-CD3 and CD2 stimulation, resulting in long term T cell proliferation, differentiation of cytotoxic T cells and production of large amounts of cytokines. In order to further delineate the role of CD28 in signal transduction and T cell activation, human CD28 was transfected into CD3+ murine T cell hybridomas. High levels of cell surface CD28 expression was achieved by protoplast fusion. The transfected molecule retained all the native CD28 mAb epitopes found on human T cells. In these transfectants, CD28 mAbs, similarly to CD3 mAbs, were able to induce Ca2+ mobilization, IL-2 promoter induction (measured as beta-galactosidase activity in T cells hybridomas pre-transfected with the IL-2-lac Z reporter gene), IL-2 secretion, TNF alpha production and apoptosis (observed as growth arrest and genome fragmentation). The parental host cells, or cells transfected with vector alone, responded only to mAbs to CD3. IL-2 secretion in the transfectants was obtained using either an IgM mAb to CD28 or IgG mAbs presented on the surface of IgG-FcR+ B lymphoma cells. Optimal activation via CD28 was inhibited by suboptimal concentrations of soluble CD3 mAb, suggesting an interaction between the two pathways. The immunosuppressive drugs Cyclosporin A and FK506 completely blocked CD28 and CD3 mediated IL-2 production in these transfectants whereas rapamycin had only a partial inhibitory effect. Finally, since the transfected human CD28 molecule confers full functional responsiveness to the murine T cell hybridomas without the need for costimulators such as PMA, this model is ideal for studying the structure-function relationships of the CD28 molecule as well as the transmembrane and cytoplasmic associations implied in CD28 signaling.

Animals↗
PubMed1994

Sonographic uterine predictors of pregnancy in women undergoing ovulation induction for assisted reproductive treatments.

OBJECTIVE: To determine preovulatory uterine sonographic predictors of pregnancy in women undergoing ovulation induction for assisted reproductive treatments. DESIGN: Prospective evaluation of uterine sonographic and vascular flow profiles in women stimulated with leuprolide acetate and hMG. SETTING: Private fertility center and tertiary-care academic center. PATIENTS: Ninety-six women underwent 102 cycles of ovulation induction for IVF (46), GIFT (20), and zygote intrafallopian transfer (36). MAIN OUTCOME MEASURES: Endometrial texture, thickness, resistance index at the first branch of uterine artery, diastolic blood flow, and pregnancy outcome (no conception, spontaneous abortion, and delivery). RESULTS: Triple-lined pattern was predominant in women who delivered liveborn infants (P < 0.005). Endometrial pattern and diastolic blood flow were the only predictive markers of term pregnancy (P < 0.001 and P < 0.05, respectively). CONCLUSION: Preovulatory triple-lined sonographic endometrial texture and the presence of end diastole blood velocities at the first branch of uterine artery are the most important uterine predictors of conception.

Adult↗
PubMed1994

Rapid induction of cytolytic T cells via CD28 stimulation for cellular immunotherapy.

One approach to adoptive cancer immunotherapy is based on the use of bispecific monoclonal antibodies (mAb) capable to redirect ex vivo generated cytolytic T lymphocytes (CTL) onto tumour cells. The efficiency of the CD28 T-cell activation pathway to induce CD3-dependent cytolytic activity was investigated while avoiding modulation of the TCR/CD3 complex needed for targeting by bispecific mAb. When used e.g. in conjunction with anti-CD2 antibodies or diacylglycerol derivatives, the in vitro stimulation of T cells with anti-CD28 mAb resulted within 36 h in high levels of CD3-dependent cytolysis (tested on a FcR+ target in the presence of anti-CD3 mAb) and sustained lymphokine production, such as TNF alpha, IFN gamma and IL-2, which may affect tumour growth when delivered locally by the transferred T cells. Rapid activation may reduce costly in vitro procedures, preserve homing capacities of retransfused T cells, and thus facilitate implementation of clinical trials based on the use of bispecific antibodies.

Antibodies, Bispecific↗
PubMed1994

Modifications of leukemic blast cells induced by in vivo high-dose recombinant interleukin-2.

High-dose recombinant human Interleukin-2 was given to 21 patients with acute myeloid (n = 11) or lymphoid (n = 10) leukemia in relapse. A rapid decrease in the peripheral leukemic blasts numbers was observed in six patients. We were unable to demonstrate at the bone marrow level a diminution in the percentage of leukemic blasts. However an increase in the expression of the adhesion molecule CD54/ICAM-1(LFA-1 ligand) affected the leukemic bone marrow blasts of these six patients. This increase in CD54 was found in eight of the 11 (73%) AML and four out of the ten (40%) ALL blasts and CD58/LFA-3 (CD2 ligand) to a lesser extent. This increased expression was not associated with modifications in the expression of MHC class II molecules. In vivo IL-2 also dramatically modified the bone marrow T-cell subsets via the increase of CD3+ cells expressing the CD45RO 'memory' marker (six out of the eight tested patients) or CD54 (seven out of the eight tested patients). Altogether these results demonstrate that leukemic blasts can be affected by in vivo IL-2 via mechanisms that could involve T cells.

Acute Disease↗