From TCR engagement to T cell activation: a kinetic view of T cell behavior.
Explore the source record for details and available documents.
Antigens↗
Biomedical subjects
A Viola
Publications and source records attributed to A Viola.
Distinct kinetics of cytokine production and cytolysis in effector and memory T cells after viral infection.
In the present study, naive T cells were compared with in vivo generated effector and memory T cells expressing the same TCR specific for lymphocytic choriomeningitis virus. Upon restimulation in vitro, the same minimal concentrations of the full agonist peptide p33 and also of weak and partial agonist peptides were required for proliferation of naive, effector and memory T cells, indicating no difference in threshold of activation. However, activation kinetics were distinct. While effector cytotoxic T cells exhibited immediate ex vivo lytic effector function, naive and memory T cells required 12 h and more exposure to antigen to develop lytic activity. However, both effector and memory T cells contained IFN-gamma mRNA in vivo and required less than 3 h for secretion of cytokines upon restimulation in vitro. In contrast, naive T cells did not contain IFN-gamma mRNA and required more than 12 h for cytokine secretion. Our results show that memory T cells exhibit a unique phenotype in that they produce cytokines and commit to proliferation as rapidly as effector cells, whereas they resemble naive T cells in the time requirement for development of cytolytic function.
Animals↗
Complete remission in acute myeloid leukaemia with t(8;21) following treatment with G-CSF: flow cytometric analysis of in vivo and in vitro effects on cell maturation.
A 75-year-old patient diagnosed as having acute myeloid leukaemia with t(8;21) received G-CSF alone as induction therapy. Complete remission was achieved following 2 weeks of treatment. Flow cytometric analysis, performed by CD45 technique modified by the introduction of preliminary gating with LDS-751, confirmed the disappearance of blast cells along with myeloid maturation. Finally, in vitro studies demonstrated that G-CSF, as compared to other differentiation inducers, was able to induce a striking effect toward neutrophilic differentiation.
Acute Disease↗
T-cell activation and the dynamic world of rafts.
Recent evidence, indicates that T-cell receptor (TCR) triggering and T-cell activation are dynamic processes that involve various aspects of T-cell organization. In addition to the interaction between the TCR molecule and its ligand, T-cell activation depends on a combination of many other events involving coreceptor molecules, actin cytoskeleton and plasma membrane lipids. Altogether, these cell structures organize the formation of a specialized junction between the T cell and the antigen-presenting cell (APC), that plays a critical role in sustaining and amplifying TCR signalling.
Animals↗
Hb Rainier [beta145(HC2)Tyr-->Cys] in Italy. Characterization of the amino acid substitution and the DNA mutation.
A high oxygen affinity hemoglobin variant was identified in a 53-year-old male patient from Napoli (Italy), suffering from pulmonary thromboembolism and polycythemia. A detailed structural characterization of the variant hemoglobin was carried out, both at the protein and DNA levels, by a combination of DNA sequencing and allele-specific amplification techniques with mass spectrometric procedures. The amino acid substitution was found to be Tyr-->Cys, and the corresponding DNA mutation was identified as A-->G at the second position of codon 145 of the beta chain. These variations indicated the presence of Hb Rainier. Haplotype analysis of DNA polymorphisms showed that the beta-globin gene from Hb Rainier was associated with haplotype II. Moreover, structural analyses provided direct identification of an intramolecular disulphide bridge joining the newly inserted beta145Cys with beta93Cys. This is the first report of the occurrence of Hb Rainier in Italy.
Adolescent↗
Genomics and transcription analysis of human TFIID.
TFIID, a multisubunit protein comprised of TBP (TATA box-binding protein) and TAF(II)s (TBP-associated factors), has a central role in transcription initiation at class II promoters. TAF(II)s role as mediators of regulatory transcription factors, such as pRb and p53, and their involvement in signal transduction pathways suggest that some may participate in the control of cell proliferation and differentiation: therefore, they could be considered potential protooncogenes or antioncogenes. With the aim of starting to analyse these potential roles, we have determined the genomic position of nine human TAF(II) genes (TAF[II]250, TAF[II]135, TAF[II]100, TAF[II]80, TAF[II]55, TAF[II]43, TAF[II]31, TAF[II]28, TAF[II]20/15) and of two previously unknown sequences related to TAF(II)250 and TAF(II)31, respectively. Except for those encoding TAF(II)250 and TAF(II)31, these genes are present in a single copy and, with the exclusion of those for TAF(II)43 and TAF(II)28 (both at 6p21), are localized in different segments of the genome. Indeed, six of them map to a chromosomal region commonly altered in specific neoplasias, which defines them as candidates for involvement in oncogenesis. Our experiments also demonstrate that TAF(II) transcripts are synthesized ubiquitously, mostly at low levels similar to those of TBP. Interestingly, the amount of the major mRNA species detected by TAF(II)20/15 cDNA is higher, which suggests that the polypeptide it encodes may also perform functions independently of TFIID. TAF(II) isoforms, indicated by additional bands on Northern blots, may play a role in modulation of TFIID function. These data will be useful for analysing variations of TAF(II) mRNA phenotype during cell proliferation, differentiation and development, both normal and pathological.
Animals↗
ESR studies of a series of phthalocyanines. Mechanism of phototoxicity. Comparative quantitation of O2-. using ESR spin-trapping and cytochrome c reduction techniques.
ESR experiments with 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TEMP) and the spin-trap 5,5-dimethyl pyrroline-N-oxide (DMPO) have been performed on a series of new phthalocyanines: the bis(tri-n-hexylsiloxy) silicon phthalocyanine ([(nhex)3SiO]2SiPc), the hexadecachloro zinc phthalocyanine (ZnPcCl16), the hexadecachloro aluminum phthalocyanine (AlPcCl16), the hexadecachloro aluminum phthalocyanine sulfate (HSO4AlPcCl16), whose photocytotoxicity has been studied against various leukemic and melanotic cell lines. Type I and Type II pathways occur simultaneously in DMF although the Type II seems to be prevalent. These results are not changed when the bis(tri-n-hexylsiloxy) silicon phthalocyanine is entrapped into liposomes. By contrast, the Type I process is favored in membrane models for all the perchlorinated phthalocyanines. This modified behavior may be accounted on a possible stacking of phthalocyanines in membranes and a preventing effect of axial ligands against aggregation in the case of the bis(tri-n-hexylsiloxy) silicon phthalocyanine. The photodynamic action of zinc perchlorinated phthalocyanine is not dependent on singlet oxygen, phototoxicity of this molecule being essentially mediated by oxygen free radicals. Quantitation of the superoxide radical was accomplished, with good agreement, by two techniques: the cytochrome c reduction and the ESR quantitation based on the double integration of the first derivative of the ESR signal. The disproportionation of the superoxide radical or degradation of the spin-trap seem to be avoided in aprotic solvents such as DMF.
Cyclic N-Oxides↗
Quantitative contribution of CD4 and CD8 to T cell antigen receptor serial triggering.
CD4 and CD8 are thought to function as coreceptors by binding to the cognate major histocompatibility complex (MHC) molecules recognized by the T cell antigen receptor (TCR) and initiating the signal transduction cascade. We report that during T cell-antigen-presenting cell interaction, triggered TCRs and coreceptors are downregulated and degraded with identical kinetics. This coordinated disappearance takes place whenever the TCR is triggered, even when the coreceptor does not engage the cognate MHC molecule and is the consequence of binding of the coreceptor-associated Lck to ZAP-70. The interaction of coreceptor and cognate MHC molecules is dispensable when T cells are stimulated by optimal ligands, but becomes crucial when suboptimal ligands are used. In the latter case the coreceptor increases the efficiency of TCR triggering without changing the activation threshold or the quality of the T cell response.
CD4 Antigens↗
A T cell receptor (TCR) antagonist competitively inhibits serial TCR triggering by low-affinity ligands, but does not affect triggering by high-affinity anti-CD3 antibodies.
It has been demonstrated that modified peptides which fail to induce detectable T cell responses can act as T cell receptor (TCR) antagonists when presented together with agonist by the same antigen-presenting cell (APC). We report that a TCR antagonist competitively inhibits TCR triggering induced by low-affinity ligands such as agonistic peptides or bacterial superantigens. However, the same antagonist cannot inhibit TCR triggering and T cell activation induced by high-affinity anti-CD3 antibodies that engage most TCR at once. These results indicate that TCR antagonists inhibit T cell responses by interfering with the ongoing process of serial triggering, rather than by delivering an inhibitory signal to T cells.
Antibodies, Monoclonal↗
Phototoxicity of some novel porphyrin hybrids against the human leukemic cell line TF-1.
Photodynamic induced cytotoxicity by porphyrin-DNA cross linker/intercalator hybrid diads and triads has been studied on the human leukemic cell line TF-1. Cells were incubated for 1 to 4 h with these new photosensitizers and irradiated with white light. Cell survival was assessed by the propidium iodide staining, using flow cytometry analysis. A comparison of the dark and light cell survival factor values suggests that irradiation has a significant effect on the toxicity at low concentrations for the porphyrin-chlorambucil diad and to a lesser extent at high concentrations for the porphyrin-acridone diad, the porphyrin-acridine diad and the porphyrin-cholic acid-chlorambucil triad. While the intrinsic antileukemic (via DNA cross-linking) activity of the chlorambucil moiety and the structural details may be responsible for the photoenhancement of the toxicity, the presence of acridine or acridone which are avid intercalators of DNA, is responsible for a similar effect seen for diads.
Acridines↗
Compound heterozygosity for Hb Lepore-Boston and Hb Neapolis (Dhonburi) [beta 126(H4)Val-->Gly] in a patient from Naples, Italy.
The simultaneous presence of two hemoglobin variants has been detected in a 14-month-old patient affected by thalassemia intermedia. The two variants were characterized by a combination of allele-specific amplification methods and mass spectrometric procedures carried out on isolated globins. These were identified as Hb Lepore-Boston and Hb Neapolis (also known as Hb Dhonburi) or beta 126 (H4)Val-->Gly. Hb Lepore-Boston is the most common hybrid variant detected in Campania and several cases of Hb Neapolis which causes a mild hypochromic microcytic anemia have been identified in this region in the last few years. This is the first report of a double heterozygosity involving Hb Lepore-Boston and Hb Neapolis.
Follow-Up Studies↗
[Dynamic phototherapy: study of anti-tumour potentialities of bis (tri n-hexylsiloxy) silicon phthalocyanine on malignant achromic M6 melanocytes. EPR study of phototoxic mechanism].
Photodynamic therapy of cancerous cells is a technique relying upon the irradiation of tumorous cells after selective incorporation of a photosensitizer. The bis (tri n-hexylsiloxy) silicon phthalocyanine is a second generation photosensitizer. Anti-cancerous potentialities of this molecule have been evaluated against the melanotic M6 cell line. Results have evidenced a high phototoxicity at low concentration and no dark toxicity under the same conditions. EPR studies on the photochemical pathways involved in phototoxicity processes have been realised in solvent and model membranes (liposomes). Results provide evidences for the production of singlet oxygen (1O2) as well as superoxide (02(o)-) and hydroxyl radicals (0OH).
Antineoplastic Agents↗
T cell activation determined by T cell receptor number and tunable thresholds.
The requirements for T cell activation have been reported to vary widely depending on the state of the T cell, the type of antigen-presenting cell, and the nature of the T cell receptor (TCR) ligand. A unitary requirement for T cell responses was revealed by measurement of the number of triggered TCRs. Irrespective of the nature of the triggering ligand, T cells "counted" the number of triggered TCRs and responded when a threshold of approximately 8000 TCRs was reached. The capacity to reach the activation threshold was severely compromised by a reduction in the number of TCRs. Costimulatory signals lowered the activation threshold to approximately 1500 TCRs, thus making T cells more sensitive to antigenic stimulation.
Antibodies↗
Electron paramagnetic resonance evidence of the generation of superoxide (O2.-) and hydroxyl (.OH) radicals by irradiation of a new photodynamic therapy photosensitizer, Victoria Blue BO.
Electron paramagnetic resonance (EPR) experiments were performed on Victoria Blue BO, a cationic dye whose photocytotoxicity has been studied against the human leukaemic cell lines K-562 and TF-1. EPR experiments with 2,2,6,6-tetramethyl-4-piperidone and spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide showed that, on illumination in aerated aqueous solution or DL-alpha-dipalmitoylphosphatidylcholine liposomes, photoexcited Victoria Blue BO is unable to generate 1O2, whereas O2.- and .OH are trapped by 5,5-dimethyl-1-pyrroline-N-oxide in the presence or absence of electron donors. The O2.- formed probably leads to the .OH radical, with an efficiency which is increased by electron donors such as FE2+.
1,2-Dipalmitoylphosphatidylcholine↗
Genomic localization of the human gene encoding Dr1, a negative modulator of transcription of class II and class III genes.
Dr1 is a nuclear protein of 19 kDa that exists in the nucleoplasm as a homotetramer. By binding to TBP (the DNA-binding subunit of TFIID, and also a subunit of SL1 and TFIIIB), the protein blocks class II and class III preinitiation complex assembly, thus repressing the activity of the corresponding promoters. Since transcription of class I genes is unaffected by Dr1. it has been proposed that the protein may coordinate the expression of class I, class II and class III genes. By somatic cell genetics and fluorescence in situ hybridization, we have localized the gene (DR1), present in the genome of higher eukaryotes as a single copy, to human chromosome region 1p21-->p13. The nucleotide sequence conservation of the coding segment of the gene, as determined by Noah's ark blot analysis, and its ubiquitous transcription suggest that Dr1 has an important biological role, which could be related to the negative control of cell proliferation.
Animals↗
Identification of the -92 (C-->T) mutation by the amplification refractory mutation system in southern Italy.
Explore the source record for details and available documents.
Base Sequence↗
DNA polymorphisms associated with Hb D-Los Angeles [beta 121(GH4)Glu-->Gln] in southern Italy.
We detected Hb D-Los Angeles [beta 121(GH4)Glu-->Gln], the most common hemoglobin variant after Hb S and Hb Lepore-Boston, in six unrelated families in Southern Italy. Ten patients were studied; eight patients were heterozygotes and two were compound heterozygotes for the hemoglobin variant and the beta-thalassemia codon 39 (C-->T) nonsense mutation. The beta-globin gene sequence was characterized by polymerase chain reaction direct sequencing; restriction fragment length polymorphisms were defined by Southern blot analysis. The gene variant, due to the GAA-->CAA substitution at codon 121, was found in association with the 5' subhaplotype [+ - - - -] and the beta-globin gene framework 1; in addition, it was found to be associated with the absence of Ava II/phi beta and Xmn I/5'G gamma, and with the presence of Hpa I/3' beta. This restriction fragment length polymorphism haplotype is common in the Mediterranean area as well as in other populations. The findings are equally compatible with an independent origin in the Mediterranean area or with origin in Asia and subsequent spread to Italy.
Base Sequence↗
Hb O-Arab [beta 121(GH4)Glu-->Lys]: association with DNA polymorphisms of African ancestry in two Mediterranean families.
Hb O-Arab [beta 121(GH4)Glu-->Lys] was detected in two Mediterranean families, one from Southern Italy and the other from Albania. The GAA-->AAA mutation at codon 121 was characterized by DNA sequencing. The mutant genes were associated with the same beta-globin gene framework variant and with the rare Hpa I/3' beta polymorphic restriction site generating a 7.0 kb fragment. However, at 5' the gene of the Italian family was associated with the restriction fragment length polymorphism subhaplotype [+ - - - +] and the Taq I/3'G gamma polymorphic site, while that of the Albanian family was associated with subhaplotype [- - - - +] but not with the Taq I/3'G gamma site. The particular features of these polymorphisms support the hypothesis of an African origin for the Hb O-Arab gene and a subsequent recombination event leading to the haplotype found in the Italian family.
Adolescent↗