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S C Meuer

Publications and source records attributed to S C Meuer.

At least 37 records · Page 2Linked to original sources
PubMed1997

The receptor function of CD2 in human CD2 transgenic mice is based on highly conserved associations with signal transduction molecules.

The activation of human T cells via CD2 in response to mitogenic monoclonal antibodies (mAbs) typically requires that one mAb is specific for an epitope within the N-terminal Ig domain of CD2 and the other for a partially hidden epitope. We have examined the proliferative response of human T cells and human CD2 (huCD2) transgenic murine T cells to two novel CD2 monoclonal antibodies, AICD2.M1 and AICD2.M2, and have partially mapped the epitopes of these and other mitogenic CD2-specific monoclonal antibodies by way of recognition of CD2:CD58 chimeric proteins possessing either the N-terminal or the membrane proximal immunoglobulin domains of CD2. To understand the molecular basis of proliferation in huCD2 transgenic murine T cells, the interactions of huCD2 with signaling proteins in murine T cells were analyzed. The transgenic huCD2 molecule was found to interact with the murine tyrosine kinases p56lck and p59fyn and the CD3-epsilon and zeta chains of the TCR/CD3 signaling complex and to coimmunoprecipitate tyrosine phosphatase activity. These molecular associations resemble the situation in human T cells and suggest that human CD2 couples to the same signal transduction pathways in humans and transgenic mice.

Animals↗
PubMed1997

Molecular cloning of SKAP55, a novel protein that associates with the protein tyrosine kinase p59fyn in human T-lymphocytes.

In human T-lymphocytes the Src family protein tyrosine kinase p59(fyn) associates with three phosphoproteins of 43, 55, and 85 kDa (pp43, pp55, and pp85). Employing a GST-Fyn-Src homology 2 (SH2) domain fusion protein pp55 was purified from lysates of Jurkat T-cells. Molecular cloning of the pp55 cDNA reveals that the pp55 gene codes for a so far nondescribed polypeptide of 359 amino acids that comprises a pleckstrin homology domain, a C-terminal SH3 domain, as well as several potential tyrosine phosphorylation sites, among which one fulfills the criteria to bind Src-like SH2 domains with high affinity. Consistent with this observation, pp55 selectively binds to isolated SH2 domains of Lck, Lyn, Src, and Fyn but not to the SH2 domains of ZAP70, Syk, Shc, SLP-76, Grb2, phosphatidylinositol 3-kinase, and c-abl in vitro. Based on these properties the protein was termed SKAP55 (src kinase-associated phosphoprotein of 55 kDa). Northern blot analysis shows that SKAP55 mRNA is preferentially expressed in lymphatic tissues. SKAP55 is detected in resting human T-lymphocytes as a constitutively tyrosine phosphorylated protein that selectively interacts with p59(fyn). These data suggest that SKAP55 represents a novel adaptor protein likely involved in Fyn-mediated signaling in human T-lymphocytes.

Amino Acid Sequence↗
PubMed1997

Differential function of CD80- and CD86-transfected human melanoma cells in the presence of IL-12 and IFN-gamma.

Introduction of co-stimulatory molecules like CD80 and CD86 represents a means to augment the immunogenicity of tumor cells and to induce immune responses directed at tumor antigens. Here we compared CD80- and CD86-transfected human melanoma cells to induce primary immune responses by their capacity to promote proliferation of human allogeneic resting T lymphocytes. CD80- and CD86-transfected SkMel63 melanoma cells induced T cell activation to a comparable degree, which was found to be independent of the cell surface density of these co-stimulatory molecules. Co-expression of CD80 and CD86 did not result in a synergistic increase in T cell proliferation. Both CD80 and CD86 transfectants induced the proliferation of isolated CD4+ or CD8+ T cells. Exogenous IL-2, IL-4 and tumor necrosis factor-alpha respectively enhanced primary T cell proliferation independent of CD80 or CD86 expression. Interestingly, differential activities of CD80 and CD86 were observed following stimulation of resting T cells in the presence of IL-12. Whereas IL-12 increased T cell proliferation in the presence of CD86-transfected melanoma cells, it exhibited an inhibitory function in the presence of CD80-expressing SkMel63 cells. Experimental evidence indicates that this inhibitory effect was mediated by IFN-gamma since (I) IFN-gamma secretion of stimulated T cells was augmented by IL-12, (II) exogenous IFN-gamma also inhibited T cell proliferation induced by CD80- but not CD86-transfected SkMel63 cells and (III) the inhibitory effect of IL-12 was blocked by an anti-IFN-gamma mAb.

Antigens, CD↗
PubMed1996

Dephosphorylation of serine 3 regulates nuclear translocation of cofilin.

Signal transduction processes in T-cells and other cell types alter the phosphorylation state of cofilin, an actin-binding phosphoprotein. Whether reversible phosphorylation is responsible for the regulation of the functional activities of cofilin is not clear at present. Here we have identified the phosphoacceptor site of cofilin and analyzed the role of cofilin phosphorylation with respect to its subcellular localization. Site-directed mutagenesis studies show that phosphorylation occurs exclusively on Ser-3. Expression of non-phosphorylatable mutant cofilin proteins in NIH3T3 cells and determination of their subcellular localization by confocal laser scanning microscopy reveal that non-phosphorylated cofilin accumulates within nuclei. This analysis shows that the subcellular localization of cofilin depends on the phosphorylation state of Ser-3.

3T3 Cells↗
PubMed1996

Inhibition of constitutive serine phosphatase activity in T lymphoma cells results in phosphorylation of pp19/cofilin and induces apoptosis.

In untransformed T lymphocytes, pp19/cofilin, a cytoplasmic actin-binding protein, undergoes dephosphorylation and nuclear translocation in response to costimulation through accessory receptors (e.g., CD2), but not following TCR/CD3 triggering. In malignant T lymphoma cells, dephosphorylation and nuclear translocation of pp19/cofilin occur spontaneously through constitutive activation of a serine phosphatase. Blockade of these processes by the serine phosphatase inhibitor okadaic acid leads to apoptosis. Moreover, lowering the intracellular pp19/cofilin concentrations by antisense-cofilin transfection results in reduced cloning efficiencies. These findings provide support for the view that pp19/cofilin plays a critical role in the growth and survival of both untransformed and malignant T lymphocytes.

Actin Depolymerizing Factors↗
PubMed1996

The outer surface lipoprotein OspA of Borrelia burgdorferi provides co-stimulatory signals to normal human peripheral CD4+ and CD8+ T lymphocytes.

Studies in man and mice have indicated that T cells induced during Borrelia burgdorferi infection are involved in the pathogenesis of the disease. We analyzed the ability of B. burgdorferi to provide co-stimulatory signals to highly enriched normal human CD2+ T lymphocytes in the presence of suboptimal concentrations of immobilized anti-CD3 antibodies. Here we show that the lipid-containing recombinant outer surface lipoprotein A (rlip-OspA) of B. burgdorferi but not its delipidated derivative rNS1-OspA augmented CD3-induced T cell proliferation in a dose-dependent manner and at levels similar to that obtained with anti-CD28 antibodies. Lipopolysaccharide had no effect in this system at any concentration tested, suggesting that the active principle of co-stimulation is associated with the lipid moiety of rlip-OspA and distinct from conventional lipid A. Furthermore, incubation of CD2+ T cells or selected CD4+ as well as CD8+ subpopulations with rlip-OspA, but not with rNS1-OspA led to the production of interferon (IFN)-gamma, interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha, but not IL-4. In contrast, co-stimulation of the respective T cell populations with anti-CD28 antibodies resulted in the generation of IFN-gamma, IL-4 and TNF-alpha, but not IL-6. This indicated that the signal transduction pathway induced by rlip-OspA is distinct from that elicited via the CD28 receptor. Co-stimulation of T cells with rlip-OspA also resulted in the development of cytolytic effector cells. In light of the fact that inflamed tissues of B. burgdorferi-infected hosts contain blood leukocytes together with spirochetes, their degradation products, or both, these results suggest that infiltrating CD4+ and CD8+ T cells of any specificities, including spirochetes, autoantigens, or both, participate in the pathogenesis of Lyme disease.

Adjuvants, Immunologic↗
PubMed1996

Differential interaction of the CD2 extracellular and intracellular domains with the tyrosine phosphatase CD45 and the zeta chain of the TCR/CD3/zeta complex.

T cell activation via CD2 requires interaction of CD2 with several signaling molecules. To investigate the structural requirements for an association of CD2 with the tyrosine phosphatase CD45 and the zeta chain of the T cell receptor (TCR)/CD3/zeta complex, we have expressed in mouse EL4 T cells a series of human CD2 chimeric and mutant proteins. Chimeric proteins in which the CD2 transmembrane and/or cytoplasmic domains were deleted or exchanged with analogous regions of CD4, CD28 or CD58 retained association with high levels of murine CD45 phosphatase activity, suggesting that the CD2 extracellular domain largely controls interaction with CD45. To a lesser extent, the cytoplasmic domain of CD2 was also shown to interact with CD45, as demonstrated by an increase in co-immunoprecipitated phosphatase activity observed following replacement of the CD58 cytoplasmic domain with that of CD2. In contrast, the cytoplasmic domain of CD2 was found to be responsible for the majority of CD2 interaction with the zeta chain of the TCR/CD3/zeta complex. Deletion of the CD2 cytoplasmic domain, excluding the first three amino acids, removed virtually all CD2 associated zeta chain and approximately sevenfold higher levels of zeta chain were found in association with a CD58/58/2 chimera than with control human CD58 wild type. This study suggests that the CD2 extracellular and intracellular domains are differentially involved in regulating T cell activation through interaction with the tyrosine phosphatase CD45 and the zeta chain of the TCR/CD3/zeta complex.

Animals↗
PubMed1996

Immune reactions induced by interleukin-2 transfected colorectal cancer cells in vitro: predominant induction of lymphokine-activated killer cells.

One aim of the genetic modification of tumor cells is the generation of immunogenic variants that can be used for the induction of immune responses against tumors. We engineered the human colorectal carcinoma cell line SW480 by means of plasmid transfection to secrete interleukin (IL)-2. Transfection of SW480 cells resulted in stable IL-2 secretion at 5-30 ng/ml per 10(5) cells in 24 h and, unexpectedly, in CD54 expression on the cell surface. SW480 variants expressing IL-2 and CD54 were tested for their capacity to induce T lymphocyte activation in vitro in comparison to untransfected and CD54 transfected cells. The cytolytic effector function of a class I MHC restricted CD8+, peptide antigen specific T cell clone was augmented following expression of CD54. IL-2 secreting SW480 variants did not further increase antigen-dependent cytolysis. Primary activation of resting T lymphocytes was assessed following allogeneic stimulation. When compared with unmodified SW480 cells, CD54 expressing variants did not initiate T cell proliferation. In contrast, IL-2 secreting SW480 cells strongly promoted primary T cell proliferation. Similarly, exogenous IL-2 and SW480 cells induced T cell proliferation which was not only due to IL-2 but was dependent on tumor cells. However, following the initial wave of cell growth in response to IL-2 secreting SW480 cells T lymphocytes could not be restimulated with SW480 or IL-2 secreting variants and could not be further expanded. T cells initially activated by IL-2 secreting SW480 cells exhibited cytolytic activity towards SW480 cells. This reactivity, however, was transient and completely blocked by K562 cells, suggesting MHC-unrestricted, nonspecific cytotoxicity. We conclude that endogenous IL-2 secretion by the colorectal carcinoma cell line SW480 does not result in the activation of MHC restricted specific T lymphocytes but predominantly induces lymphokine-activated killer cells. Considering that tumor cell vaccines are aimed at inducing tumor-specific immune responses, our in vitro observation would rather argue against the in vivo application of such a tumor cell modification in colorectal cancer.

Amino Acid Sequence↗
PubMed1996

Epidemiologic investigation of serum levels of the soluble forms of CD25, CD54 and CD58, and T cell responsiveness after stimulation via the CD2-dependent pathway in a random sample of the general population.

A sero-epidemiologic correlation study on immune parameters which would correlate with the frequency of common colds (FCC) had been conducted in 1992. There, an inverse relationship between circulating adhesion molecules CD54 and CD58 and FCC was found. Eighteen months later we performed an analogous assessment in order to verify the previous findings and to carry out additional experiments including in vitro proliferative responses of T cells and their production of various cytokines (IFN-gamma, IL-2, IL-6 and IL-10). The additional examinations showed that individuals with frequent common colds exert a higher T cell proliferation and higher production of cytokines than persons which experience never or few common cold infections. These findings could be confirmed statistically. Taken together, the results suggest consistently in individuals with frequent common colds an association with low serum levels of the immunosuppressive soluble adhesion molecules sCD54 and sCD58, high proliferation of unstimulated and stimulated T cells and secretion of higher concentrations of cytokines (IFN-gamma, IL-2, IL-6 and IL-10) into the cell culture supernatants.

Age Factors↗
PubMed1995

Amino acid residues required for binding of lymphocyte function-associated antigen 3 (CD58) to its counter-receptor CD2.

Efficient activation and regulation of the cellular immune response requires engagement of T cell accessory molecules as well as the antigen-specific T cell receptor. The lymphocyte function-associated antigen (LFA) 3 (CD58)/CD2 accessory pathway, one of the first discovered, has been extensively characterized in terms of structure and function of the CD2 molecule, which is present on all T lymphocytes and natural killer cells of the human immune system. The binding site of human CD2 for LFA-3 has been localized to two epitopes on one face of the first immunoglobulin (Ig)-like domain of this two-domain, Ig superfamily molecule. Human LFA-3 is genetically linked and is 21% identical in amino acid sequence to CD2, suggesting that this adhesive pair may have evolved from a single ancestral molecule. We have aligned the amino acid sequences of LFA-3 and CD2 and mutagenized selected amino acids in the first domain of LFA-3 that are analogous to those implicated in the binding site of CD2. The data show that K30 and K34, in the predicted C-C' loop, and D84, in the predicted F-G loop of LFA-3, are involved in binding to CD2, suggesting that two complementary sites on one face of the first domain of each molecule bind to each other.

Amino Acid Sequence↗
PubMed1995

Human T lymphocyte activation induces tyrosine phosphorylation of alpha-tubulin and its association with the SH2 domain of the p59fyn protein tyrosine kinase.

A glutathione-S-transferase-src-homology domain 2 (GST-SH2) fusion protein was employed to identify molecules interacting with the protein tyrosine kinase p59fyn. Among several proteins which bound to the fyn SH2 domain in lysates of human Jurkat T lymphocytes, alpha- and beta-tubulin were identified by N-terminal sequencing. Further analysis established that alpha-tubulin exists as a tyrosine-phosphorylated protein in Jurkat cells, where it interacts with p59fyn, but not with p56lck. By contrast, in untransformed resting human T lymphocytes alpha-tubulin is not detectable as a tyrosine phosphorylated protein. However, following T cell activation, it becomes rapidly phosphorylated on tyrosine residues and subsequently associates with the SH2 domain of fyn. Interestingly, constitutively tyrosine-phosphorylated alpha-tubulin that is able to interact with the fyn-SH2 domain is expressed in peripheral blood T lymphoblasts isolated from leukemic patients in the absence of external stimulation.

Amino Acid Sequence↗
PubMed1995

Cytokine messenger RNA expression and proliferation status of intestinal mononuclear cells in noninflamed gut and Crohn's disease.

T-cell activation and local cytokine production probably contribute to the pathogenesis of Crohn's disease. This study investigates the proliferative status of intestinal mononuclear cells (MNC) and cytokine messenger RNA (mRNA) production in gut tissue sections from patients with Crohn's disease and noninflamed controls. mRNA in situ hybridization was performed using 33P-labelled riboprobes for human interleukin (IL)-1 beta, IL-2, IL-4, IL-5, IL-6, tumour necrosis factor-alpha and interferon-gamma. The expression of the proliferation-associated antigen Ki-67 was analysed by immunohistochemical single and double staining. Compared with controls, where proliferation of MNC and cytokine expression was restricted to mucosal lymphoid follicles, inflamed gut tissue contained increased numbers of cells expressing cytokine mRNA, most prominently IL-1 beta and IL-6, but also interferon-gamma and tumour necrosis factor-alpha. Proliferating T-cells were increased in number, and small amounts of IL-2-expressing cells were detected. IL-4 was expressed by a few cells exclusively in follicular germinal centres. IL-5 was negative. Proinflammatory cytokines are strongly expressed in situ in Crohn's disease and largely predominate over lymphokine mRNA. Our results provide in situ evidence of a local lymphocyte response in Crohn's disease with characteristics of a delayed-type hypersensitivity reaction.

Adolescent↗
PubMed1995

Development of immunogenic colorectal cancer cell lines for vaccination: expression of CD80 (B7.1) is not sufficient to restore impaired primary T cell activation in vitro.

The capacity of colorectal carcinoma and melanoma cell lines to induce primary versus effector T lymphocyte activation in vitro was investigated. Established epithelial tumour cell lines derived from colorectal carcinoma and melanoma did not activate a primary proliferative response of resting T lymphocytes in allogeneic mixed lymphocyte tumour cell cultures (MLTCs). In contrast, the same tumour cells were effectively lysed by preactivated cytolytic T cell clones. This demonstrates that tumour cells are impaired in inducing a primary immune response but are susceptible to effector immune responses. Attempts at improving primary T cell activation revealed that exogenous cytokines, including interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha) and interleukin-2 (IL-2), were not effective. Expression of CD80 (B7.1), by transfecting a CD80 cDNA into the melanoma cell line SkMel63, improved T cell proliferation considerably. In contrast, CD80 expression in two colorectal carcinoma cell lines (SW480, SW707) did not result in T cell activation. This was not due to lack of class II MHC expression on SW480 since coexpression of a HLA-DR3 alloantigen and CD80 had no effect. Our data suggest that de novo CD80 expression is not, in general, sufficient to improve primary T cell activation by human tumour cells.

Antigens, Neoplasm↗
PubMed1995

Activation of lamina propria T lymphocytes in Crohn's disease.

Crohn's disease is characterized by chronic inflammatory infiltrates and granuloma formation in the gut. T cell directed immunotherapy appears to be effective in relieving these symptoms. Under normal conditions, lamina propria T lymphocytes have a low proliferative response to antigen receptor stimulation in vitro due to the influence of the local intestinal environment. This study shows that lamina propria T lymphocytes exhibit an enhanced response to antigen receptor stimulation in active Crohn's disease, which may contribute in its pathogenesis.

CD3 Complex↗
PubMed1995

Accessory signals for growth and differentiation of human T lymphocytes.

Accessory signals represent the level at which functional immune responses are regulated. Impairment of ligand-receptor interactions or, alternatively, intracellular signalling processes plays a pivotal part in vivo. Thus, tumour tolerance might result from missing co-stimulatory signals, which is supported by numerous recent data. Conversely, blocking accessory receptors might provide the means to influence allograft rejection. Upregulation of accessory receptors and their ligands is a hallmark of inflammatory reactions. Finally, given that particular microenvironments are characterized by the presence of particular combinations of ligand molecules for critical accessory receptors on T lymphocytes, one could envisage novel approaches to local immune intervention. All these perspectives, however, are based on our understanding of how accessory receptors are composed and interact with intracellular enzymes, which all together transmit critical signals to the nucleus, and on an understanding of how these signals contribute to functional T cell behaviour.

Animals↗