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Molecular Mechanisms Of T Cell Co Stimulation And Co Inhibition Pdf

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Co-stimulation is a secondary signal which immune cells rely on to activate an immune response in the presence of an antigen -presenting cell.

After decades of extensive research in the development of cancer immunotherapies, during the last ten years these therapies have achieved clinical success. Among the most promising approaches is the blockade of immune checkpoints that regulate immune responses. T cell antigen recognition is highly regulated by co-stimulatory positive and negative signals.

Co-stimulation

The results show that maximal activation of the IL-2 gene requires activation of at least two different protein kinase cascades, i. Stimulation of TCR alone is, however, insufficient to induce proliferation and synthesis of the ultimate mitogen, IL-2, rather causing a state of clonal anergy reviewed in 1,2.

In combination with additional signals—triggered by either accessory molecules or cytokines—T cells become optimally activated 3 — 5. Whether the IL-1 signal plays an enhancing or obligatory role in T cell activation is discussed controversially. More importantly, the molecular mechanisms underlying the co-stimulatory activity of IL-1 still remain unclear. Several signal transduction cascades have been implied to be involved in the control of the IL-2 enhancer 6 — 8.

This is consistent with the finding that T cell activation requires co-stimulatory signals in addition to those activated via the TCR—CD3 complex How these distinct stimuli act synergistically to cause T cell activation has not been fully elucidated. The latter two groups of MAPK i. Activation of MAPK pathways results in phosphorylation of transcription factors, thereby transducing signals from cell surface receptors to the nucleus.

Simultaneous stimulation of distinct MAPK cascades via two different cell surface receptors might therefore amplify a signal by converging on the same effector molecules e. To get insight into the molecular events being responsible for ILinduced co-stimulatory activity in T cells, activation of distinct MAPK cascades as well as their involvement in regulation of IL-2 gene transcription have been investigated in the murine thymoma cell line EL4, expressing high numbers of functionally active TCR and IL-1 receptors IL-1R.

Gaestel Berlin, Germany. The EL-4 subline was a kind gift of Dr R. McDonald Lausanne, Switzerland. Prior to treatment cells were serum starved for 12—14 h. Cells were then stimulated with 2. The cell suspension was filtered through nylon wool and washed 3 times with RPMI medium. Before stimulation cells were washed 3 times with RPMI medium then incubated with 2. Prior to incubation with a specific antibody preclearing was carried out with Protein A—Sepharose for 1 h. Then 1 mg of cytosolic protein was precipitated with ng of a MEK-1 specific antibody bound to Protein A—Sepharose.

The assay was performed as described recently Briefly, after stimulation, samples of 10 7 cells were washed and cytosol prepared as described in Beads were recovered at 10, g for 5 min and washed twice in lysis buffer. Recovery of the enzyme was confirmed by detecting the amount of p38 MAPK by means of a specific antibody. The binding reaction was carried out with radiolabeled double-stranded oligonucleotide 0. Cells were washed and stimulated with anti-CD3 antibodies, IL-1 or their combination for 18 h.

As shown in Fig. Practically all cells possessed both receptors Fig. To ensure that both receptors were functionally active, IL-2 synthesis was measured in activated cells. Upon combination of both stimuli IL-2 synthesis was markedly enhanced, i. In order to investigate whether distinct signal transduction pathways were involved in activation of IL-2 synthesis, protein kinase cascades stimulated via the TCR or IL-1R were studied in detail.

Treatment of the cells with IL-1 led to a time-dependent enhancement of c-Jun phosphorylation compared to the control Fig. In contrast, stimulation with anti-CD3 antibodies did not affect c-Jun phosphorylation data not shown. Similar results were obtained in stimulated murine spleen lymphocytes. Because IL-2 synthesis was activated synergistically by anti-CD3 and IL-1, and both stimuli activated different MAPK cascades, it was obvious to study the activation of transcription factors involved in the regulation of the IL-2 promoter.

In anti-CD3-treated cells elevated NFAT binding was observed after 30 min of stimulation that declined to control levels after min. In cells stimulated through both receptors NFAT was activated in a biphasic manner. The connection between activation of different protein kinase cascades and transcription factors regulating the IL-2 promoter was investigated by specific protein kinase inhibitors PD, a specific inhibitor of MEK-1, and SB, a specific inhibitor of p38 MAPK.

To establish a link between activation of different protein kinase cascades and regulation of IL-2 synthesis, the influence of specific protein kinase inhibitors on TCR- and ILstimulated IL-2 synthesis has been investigated. The influence of specific protein kinase inhibitors on IL-2 synthesis induced by co-stimulation with anti-CD3 and IL-1 is shown in Fig.

Preincubation of the cells with the combination of both inhibitors resulted in a further decrease in ILspecific mRNA level Fig.

The data imply that at least two groups of MAPK, i. The results imply that several protein kinase cascades have to be activated and converge at the level of IL-2 gene transcription for induction of maximal IL-2 synthesis. ILinduced activation of both protein kinases was less prominent in splenic lymphocytes as compared to thymoma cells. This finding is, however, not surprising considering the significantly lower amounts of JNK and p38 MAPK proteins of splenic lymphocytes compared to thymoma cells data not shown.

However, it is obvious to speculate that phosphorylation by p38 MAPK of well-defined molecular targets like ATF-2 or Elk-1 or of some transcription factors not identified so far might participate in transcriptional regulation in T lymphocytes similar to several other cells Furthermore, p38 MAPK might be involved in the post-transcriptional regulation, i.

It is well documented that JNK family protein kinases phosphorylate the N- terminal activation domain of c-Jun resulting in activation of the transcription factor. Besides activating c-Jun, JNK also enhance the transcriptional activity of Jun proteins 14 , 30 , Although we have no direct evidence so far for participation of ILactivated JNK in the regulation of IL-2 synthesis, because of the lack of specific inhibitors, several reports indicated phosphorylation of c-Jun and ATF-2 , subsequent elevated nuclear binding, and expression of c-Jun protein in different cells and cell lines.

Furthermore, the JNK pathway is required for the normal regulation of AP-1 transcriptional activity 14 , 32 — These results indicate that JNK catalysed phosphorylation of its specific substrates might activate cytokine gene transcription also in T lymphocytes.

It remains to be elucidated whether TCR and IL-1 activated different members of the NFAT family or, alternatively, nuclear export and import, or rephosphorylation of NFAT were responsible for activation of the transcription factor after 3—4 h in co-stimulated cells 37 , In spite of this, NFAT proteins seem to be obvious targets of both TCR- and ILstimulated signaling cascades resulting in their activation, nuclear translocation and finally up-regulation of IL-2 gene transcription.

Although proinflammatory cytokines, e. In summary, the data clearly show that signaling pathways activated via TCR and IL-1R converge at the level of the IL-2 gene transcription, resulting in synergistically enhanced IL-2 synthesis and secretion. Maximal activation of the IL-2 gene requires activation of at least two different protein kinase cascades, e. The co-stimulatory effect of IL-1 in T cell activation might be due to convergence of different signaling pathways at the level of the IL-2 promoter resulting in enhancement of its transcriptional activity.

The results also suggest that convergence of TCR and IL-1 induced signaling cascades is obligatory for maximal IL-2 synthesis in co-stimulated cells. Flow cytometry was carried out as described under Methods. Cells 10 7 were incubated with 2. MEK-1 was immunoprecipitated with a specific antibody and its activity measured with hr-ERK-1 as substrate, as described under Methods. Results are representative for two independent experiments. JNK was immunoprecipitated and subjected to an in vitro kinase assay using hr-GST—Jun fusion protein as substrate according to Methods.

Results are representative for four independent experiments. C Cells 10 7 were incubated with 2. The reaction was stopped by the addition of activated GSH—Sepharose. Samples were shaken for 30 min, and beads recovered by centrifugation and washed. Phosphorylated GST—Jun protein was visualized by autoradiography. For further details see Methods. Lymphocytes were stimulated as described in A.

Recovery of the enzyme was confirmed by detecting the amount of p38 MAPK by means of a specific antibody lower part. Cells 10 7 were stimulated with 2. Nuclear extracts were prepared and 7. Results are representative for five independent experiments. Protein—oligonucleotide complexes were separated by PAGE and visualized by autoradiography. Extraction of nuclear proteins and experimental conditions were identical with those described under A.

Results are representative for three independent experiments. Cells 10 6 were stimulated with 2. Results are means of three independent experiments. EL-4 cells 1. Cells were stimulated with anti-CD3 antibody 2. RNA was then prepared and Northern blotting performed as described under Methods. Spots were visualized by autoradiography. The competent technical assistance of Mrs M. Golombek is gratefully acknowledged. The authors thank Mrs K. Erdogan for her excellent typing assistance. Ullman, K.

Transmission of signals from the T lymphocyte antigen receptor to the genes responsible for cell proliferation and immune function: the missing link. Crabtree, G. Signal transmission between the plasma membrane and nucleus of T lymphocytes.

Collins, T. Adhesion receptors in lymphocyte activation. Rudd, C. Today 15 : June, C. The B7 and CD28 receptor families.

Co-signal Molecules in T Cell Activation

Perspective Free access Address correspondence to: Craig B. Phone: ; Fax: ; E-mail: drt mail. Find articles by Frauwirth, K. Find articles by Thompson, C.

Abstract: T cell costimulatory and coinhibitory pathways are essential orchestrators and regulators of the adaptive immune response. In recent years, the costimulatory CD28 receptor and B7 ligand families have been expanded to include a total of four and seven members, respectively. Several polymorphisms, mutations, and deletions in both regulatory and protein-coding regions of these genes have subsequently been discovered and evaluated for genetic linkage to various human diseases. Here, we review this evidence as we discuss T cell costimulation and coinhibition in the context of genetic susceptibility to autoimmunity, cancer, and other diseases. As we gain further insight into the functional significance and mechanism of these immunoregulatory pathways by both genetic and immunological approaches, these receptors and ligands are poised to become key targets for immunotherapy. The vertebrate immune system is regularly challenged to mount an immune response of appropriate specificity and magnitude to a vast array of foreign antigens, while restraining potentially deleterious responses to self and harmless environmental antigens. This requires a profound regulation of the immune response, especially at the level of the T cell , as these lymphocytes bear a central role in adaptive immunity and contribute to the cytokine milieu in which elements of innate immunity operate as well.

The results show that maximal activation of the IL-2 gene requires activation of at least two different protein kinase cascades, i. Stimulation of TCR alone is, however, insufficient to induce proliferation and synthesis of the ultimate mitogen, IL-2, rather causing a state of clonal anergy reviewed in 1,2. In combination with additional signals—triggered by either accessory molecules or cytokines—T cells become optimally activated 3 — 5. Whether the IL-1 signal plays an enhancing or obligatory role in T cell activation is discussed controversially. More importantly, the molecular mechanisms underlying the co-stimulatory activity of IL-1 still remain unclear.


Request PDF | On Jun 5, , Lieping Chen and others published Molecular mechanisms of T cell co-stimulation and co-inhibition | Find, read.


Molecular mechanisms of T cell co-stimulation and co-inhibition

It seems that you're in Germany. We have a dedicated site for Germany. This book equips young immunologists and health professionals with a clear understanding of the fundamental concepts and roles of co-signal molecules and in addition presents the latest information on co-stimulation. The first part of the book is devoted to co-signal molecules and the regulation of T cells.

Effective T cell-dependent immune responses require an antigen-specific signal through the T cell receptor TCR and simultaneous antigen non-specific signaling through a co-stimulatory receptor, whereas antigen signals alone induce anergy. Besides the prototype co-stimulatory receptor CD28, T cells also express a variety of other co-stimulatory receptors 1. However, although co-stimulation is an established crucial mechanism, there are a several generally neglected causes of uncertainty about its role. It is thus difficult to reconcile the fact that co-stimulatory signals are completely independent of TCR signaling 2 — 9 with a simple coupled enhancing effect on TCR-induced activation and this is reinforced by the abundance of co-stimulatory receptors 1.

Mechanisms of antigen presentation to T cells

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Targeting Costimulatory Molecules to Improve Antitumor Immunity

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