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S C Meuer

Publications and source records attributed to S C Meuer.

At least 73 records · Page 4Linked to original sources
PubMed1992

Phenotypical and biochemical characterization of a variant CD45R expression pattern in human leukocytes.

As a result of a regulatory polymorphism a variant pattern of CD45R expression can be found in 8% of healthy individuals. We have previously reported that all resting T cells of these individuals react with CD45RA monoclonal antibodies (mAb) that are directed to the high-molecular mass isoforms (220 and 205 kDa) of the leukocyte common antigen (CD45). In addition, their T cells remain CD45RA+ after in vitro activation. In this report we studied the regulatory CD45R polymorphism in more detail. Flow cytometry studies revealed that CD45RA antigens are weakly expressed on normal monocytes but are absent from granulocytes. In individuals displaying the variant CD45R pattern both monocytes and granulocytes were CD45RA+. In controls and variant T cells CD45RA mAb precipitated two chains with molecular masses of about 220 and 205 kDa. In activated T cells from controls (CD45RA-) neither p220 nor the p205 chain of CD45RA could be detected. However, activated T cells from variant individuals (CD45RA+) did not express p220 but expressed p205 of CD45RA. These data indicate that there is a failure to down-regulate p205 CD45RA in individuals displaying the variant CD45R expression pattern. Since their T cells lost p220 CD45RA during activation the data also suggest that the two isoforms detected by CD45RA mAb can be regulated independently.

Antigens, CD↗
PubMed1992

Four CD45/P56lck-associated phosphorproteins (pp29-pp32) undergo alterations in human T cell activation.

In human T lymphocytes a functional complex is formed between the protein tyrosine phosphatase CD45, the protein tyrosine kinase p56lck and a phosphoprotein, pp32, a possible common substrate. Here we demonstrate that the previously described pp32 protein is composed of two distinct molecules (pp29 and pp32) in both resting human T lymphocytes and continuously proliferating T lymphoma lines. Importantly, T lymphocyte activation employing CD2 monoclonal antibodies (mAb), CD3 mAb or phorbol 12, 13 dibutyrate results in loss of pp29 and pp32 from the CD45/p56lck molecular complex and concomitant association of two distinct phosphoproteins with different molecular weights (pp30 and pp31). These events appear to be unrelated to clonal T cell growth but rather depend on receptor-mediated differentiation signals. Reprecipitation experiments employing an antiserum directed at a consensus sequence of GTP-binding proteins suggest that all four pp29-pp32 molecules might represent proteins with GTP-binding properties. Biochemical analysis of pp29-pp32 employing V8-protease digestion indicates that they differ in low-molecular weight fragments of 8, 5, 4.5, 4 and 3 kDa, respectively.

Antigens, CD↗
PubMed1992

Structural and functional epitopes of the human adhesion receptor CD58 (LFA-3).

CD58 (LFA-3), a heavily glycosylated protein of 40-70 kDa, is expressed on a broad range of hematopoietic and non-hematopoietic cells. It serves as a physiological ligand of the CD2 receptor, present on T cells and natural killer cells, and plays, thus, an important role in lymphocyte adhesion and T cell activation through CD2. Whereas several epitopes and their respective function are known for CD2, a similarly detailed characterization of CD58 is still lacking. We raised a panel of novel murine monoclonal antibodies (mAb) against recombinant human CD58 and describe here the identification of six structurally and/or functionally distinct epitopes on the CD58 molecule. All epitopes were found to be present in equal numbers on a wide range of CD58+ cells, none of them being differentially up-regulated following cell activation or malignant transformation. Two of these epitopes represent functionally relevant sites, involved in binding of CD58 to CD2 and T cell activation via CD2. One further epitope appears to be selectively involved in CD58-mediated activation, whereas the other three displayed no functional effects. The new mAb allow for the first time the detection of CD58 in enzyme-linked immunosorbent assays and immunofluorescence while bound to its receptor CD2 in human serum or on freshly isolated blood cells. Finally, one mAb was found to specifically cross-react with T11TS, the equivalent of CD58 in sheep.

Animals↗
PubMed1992

Definition of immunogenic determinants of the human papillomavirus type 16 nucleoprotein E7.

Specific T lymphocyte lines and T cell clones were established from peripheral blood mononuclear cells of asymptomatic seropositive individuals employing synthetic peptides which correspond to the sequence of the human papillomavirus (HPV) type 16 transforming protein E7. Specificity analysis of T cells as determined by means of [3H] thymidine incorporation after stimulation with individual peptides revealed three immunogenic determinants of E7 that are recognised in association with at least two different HLA haplotypes. One N-terminal region (aminoacids 5-18) was recognised by one T cell line. T cell clones and the corresponding T cell line established from another donor responded to a different N-terminal (17-38) and to a C-terminal region (69-86). The N-terminal sequence 5-18 and the C-terminal determinant contain a periodicity of hydrophilic and hydrophobic residues that have been found in many T cell epitopes. Phenotypic characterisation of T cell clones by indirect immunofluorescence revealed that the T cell clones expressed the CD4 surface glycoprotein suggesting that the specific E7 determinants were recognised in association with major histocompatibility complex (MHC) class II molecules. With regard to functional properties, at least three T cell clones exhibited specific cytotoxic activity towards autologous B lymphocytes transformed by Epstein-Barr virus in the presence of the relevant HPV16 E7 peptides. The implications of these results regarding the development of vaccination strategies and host-virus interaction are discussed.

Amino Acid Sequence↗
PubMed1992

Dephosphorylation of pp19: a common second signal for human T cell activation mediated through different accessory molecules.

Accessory molecules are thought to provide essential regulatory signals for T cell activation. In order to identify specific intracellular events linked to triggering through accessory surface receptors, mAbs against CD2, CD3, CD4, and CD8 were employed to activate resting human T lymphocytes in vitro. Subsequently, intracellular phosphorylation of phosphoprotein (pp) 19, a recently identified substrate of a serine phosphatase involved in CD2 mediated T cell triggering, as well as functional parameters (responsiveness to IL-6, production of IL-2 and IFN-gamma) were determined. As in responses to CD2 mAbs, cross-linking of CD4 and/or CD8 to the TCR-CD3 complex but not CD3 cross-linking alone promoted pp19 dephosphorylation. This early event was in all cases followed by particular late functional responses, i.e. induction of IL-6 responsiveness and secretion of IL-2. In marked contrast, no relationship was found between pp19 dephosphorylation and IFN-gamma production. Taken together, a common intracellular pathway appears to exist in which signals mediated through CD2, CD4, and CD8 merge to promote monokine responsiveness and IL-2 production in human T cells. Dephosphorylation of pp19 thus appears to represent a process which is linked to critical 'second signals' involved in the generation of antigen induced T cell responses.

Antibodies, Monoclonal↗
PubMed1992

Spontaneous responsiveness to cytokines by human T-cell leukemias.

The molecular basis for autonomous growth of malignant forms of human T lymphocytes is not known. It can be investigated by functional responses of malignant cells in comparison with untransformed counterparts. At least two pathways (the CD2 and CD3 pathways) of human T-cell activation have been recently defined on the basis of monoclonal antibody activities in vitro, an experimental model exists which can be used to investigate which pathway of T-cell triggering might be involved in malignant growth. In untransformed T lymphocytes, responses to addition of cytokines are strictly controlled by signals which are mediated through triggering molecules including CD2 and CD3 and we therefore investigated 20 freshly recovered human T leukemias with regard to spontaneous growth in response to interleukins. The majority of cases (16 out of 20) investigated displayed spontaneous responsiveness to cytokines (interleukins 1, 4, and 6), which might be related to activation signals mediated through the CD2 pathway. The functional repertoire of T leukemias did not correlate with expression of differentiation antigens conventionally employed for leukemia typing.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1992

Immunomodulatory properties of soluble recombinant human CD58 (LFA-3) molecules.

The interaction between the E-rosette receptor (CD2) expressed on the cell surface of T lymphocytes and its natural ligand CD58 (LFA-3), a broadly distributed cell surface molecule, represents a potential target for immune modulation. To explore this possibility, we have expressed a soluble recombinant form of human CD58 which exerts potent biological effects in that it acts as a competitive inhibitor for cell surface CD58 in its binding to CD2 positive lymphocytes. Thus, recombinant CD58 blocks NK-mediated cytotoxicity, the mixed lymphocyte reaction, and the T lymphocyte adhesion to CD58 positive cells. In contrast, recombinant CD58 synergized with mitogenic CD2R monoclonal antibodies (anti-T11(2/3) or 9.1) in T cell triggering.

Adjuvants, Immunologic↗
PubMed1991

A serine phosphatase is involved in CD2-mediated activation of human T lymphocytes and natural killer cells.

We investigated early activation events after T cell triggering via the Ag receptor (TCR/CD3) complex as compared to activation via the CD2 surface molecule. To this end, resting peripheral human T lymphocytes were preincubated with 32P-orthophosphate and subsequently exposed to mitogenic mAb directed at either TCR/CD3 or CD2 for varying time periods. Cells were lysed and postnuclear lysates subjected to two-dimensional-gel electrophoresis (IEF and SDS-PAGE). As early as 10 min after stimulation through CD2, dephosphorylation of a cytosolic 19-kDa protein was observed. In contrast, this protein remained phosphorylated in unstimulated as well as CD3 activated T cells. Phosphoprotein (pp) 19 dephosphorylation was transient because, at later time points (2-4 h) after CD2 triggering, this protein was phosphorylated again. Phosphoaminoacid analysis indicated that pp19 is dephosphorylated on serine residues. Identical results were obtained using a CD2+ but TCR/CD3- human NK cell clone indicating that pp19 dephosphorylation occurs independent of surface expression of a TCR/CD3 complex. These data show that, in addition to protein phosphorylation events, serine dephosphorylation is involved in T cell triggering. More important, a selective signaling mechanism appears to be linked to T cell activation through the CD2 pathway.

Antibodies, Monoclonal↗
PubMed1991

Human T cell responses to IL-1 and IL-6 are dependent on signals mediated through CD2.

We investigated the involvement of IL-1 and IL-6 in activation of resting human T lymphocytes via the Ti-Ag receptor/CD3-dependent and the CD2-dependent pathways, respectively. When lymphocytes were triggered through CD3-Ti, neither IL-1 nor IL-6 nor the combination of both cytokines was capable of inducing a proliferative response, whereas addition of monocytes or IL-2 to such a system mediated DNA synthesis and cellular mitosis. In contrast, in the presence of submitogenic concentrations of mAb directed at CD2, IL-1 and/or IL-6 produced marked comitogenic dose-dependent effects. Moreover, although the action of IL-1 was clearly dependent on expression of the IL-2/IL-2R system, proliferation to CD2 antibody plus IL-6 could not be blocked by mAb directed at the IL-2R and/or IL-4. T cell responsiveness to both IL-1 and IL-6 was facilitated in the presence of CD58-like signals as delivered by human rCD58, SRBC or a mAb (anti-T111A), which binds to an interaction site for CD58 on the human CD2 molecule. These findings indicate that CD2 and its ligand CD58 play an important role in T cell/monocyte interactions during primary immune responses by means of upregulating T cell susceptibility to monocyte-derived cytokines.

Antibodies, Monoclonal↗
PubMed1991

Expression of different CD8 isoforms on distinct human lymphocyte subpopulations.

Human CD8+ lymphocyte subpopulations were analyzed for their expression of CD8 alpha and CD8 beta subunits. Investigations with uncloned peripheral blood lymphocytes as well as cloned human natural killer and T cell subpopulations demonstrate that CD3- natural killer cells, T cell receptor gamma/delta, and CD4+CD8+ T cell clones express exclusively CD8 alpha gene products. Structural analysis of CD8 molecules demonstrates that CD8 alpha+/beta- T lymphocytes surface express 75-kDa CD8 alpha/alpha homodimers whereas CD8 alpha/beta lymphocytes express concomittantly two CD8 isoforms of different molecular masses (67 kDa and 75 kDa, respectively). Peptide mapping of these latter two isoforms suggests that CD8 is expressed as alpha/alpha homodimers and alpha/beta heterodimers on CD8 alpha/beta+ cells. Importantly, we found that the two CD8 isoforms behave functionally different. Thus, in contrast to CD8 alpha/beta+/CD8 alpha/alpha+ T lymphocytes, cytolytic activity of CD8 alpha/beta-/CD8 alpha/alpha+ T cell clones was not inhibited by anti-CD8 monoclonal antibodies and the latter were not induced to proliferate following CD3/CD8 cross-linking.

Antibodies, Monoclonal↗
PubMed1991

Down-regulation of protein kinase C activation in human lamina propria T lymphocytes: influence of intestinal mucosa on T cell reactivity.

Human lamina propria T lymphocytes (LPL-T) were shown to have lower proliferative responses to CD3 triggering than autologous peripheral blood T lymphocytes (PBL-T), yet preserved their responsiveness to CD2 stimulation. In order to elucidate the basis of these differences, freshly recovered human LPL-T and autologous PBL-T were stimulated with CD2 monoclonal antibodies anti-T11(2/3) plus sheep red blood cells and phorbol 12,13-dibutyrate (PBu2) plus ionomycin, respectively. LPL-T showed invariably lower responses to PBu2 plus ionomycin than PBL-T. In contrast, LPL-T still preserved proliferation to CD2 activation even when their responses to PBu2 plus ionomycin were decreased almost to background levels. Preincubation of PBL-T with intestinal mucosa supernatant led to a similar reactivity as observed in fresh LPL-T. Moreover, the protein kinase C (PKC) inhibitor sphinganine was able to inhibit DNA synthesis to stimulation with PBu2 plus ionomycin but not to CD2 triggering. This study suggests that CD2-induced proliferation is not dependent on PKC activation and that down-regulation of PKC activation may be one of the mechanisms for inhibition of the CD3-Ti-dependent activation pathway in LPL-T by intestinal mucosa-derived influences in vivo.

Antigens↗
PubMed1991

Activation and signaling status of human lamina propria T lymphocytes.

In this study, proliferative responses of human lamina propria T lymphocytes were examined in vitro. The response of lamina propria T lymphocytes to Sepharose-bound anti-CD3 antibody plus interleukin 2 was significantly lower than the response of autologous peripheral blood T lymphocytes, whereas the responses of lamina propria T lymphocytes to anti-T11(2/3) antibodies plus sheep erythrocytes or anti-CD28 antibody plus interleukin 2 were largely preserved. After coculture with mucosa supernatant, peripheral blood T lymphocytes showed a similar pattern of reactivity as lamina propria T lymphocytes. This reduced reactivity to T-cell antigen receptor stimulation appears to exist at the level of signal transduction, because triggering of CD3 induces low amounts of intracellular inositol 1,4,5-triphosphate and no free calcium increase in lamina propria T lymphocytes when compared with peripheral blood T lymphocytes. This study indicates that the antigen receptor-dependent activation pathway of lamina propria T lymphocytes for proliferation is down-regulated by intestinal mucosa derived factor(s) and that the alternative pathways mediated by CD2 or CD28 are largely preserved. Based on previous data that lamina propria T lymphocytes can provide help to B cells, it is possible that these alternative activation pathways play an important role in T-B cell interaction in the gut.

Antibodies, Monoclonal↗
PubMed1991

Dual function of recombinant human CD58: inhibition of T cell adhesion and activation via the CD2 pathway.

To produce large quantities of recombinant CD58 (rCD58) glycoproteins for biochemical and functional studies, a cDNA clone containing the phosphatidylinositol-linked form of human CD58 was expressed in insect cells using the baculovirus system. Gel filtration showed rCD58 to form soluble oligomeric aggregates which were functionally, antigenically, and biochemically similar to their natural counterpart. Sequence analysis of the amino- and carboxy-terminal ends of released rCD58 protein revealed that the 28 amino acid signal peptide was accurately removed. In contrast, the hydrophobic C-terminal peptide was not removed. rCD58 binds to its natural ligand CD2 with a dissociation constant Kd = 5 x 10(-8) M, which is equivalent to the affinity of physiological T cell adhesion mediated by the membrane bound CD2-CD58 receptor-ligand pair. Rosette formation of human T lymphocytes with sheep and human erythrocytes was completely abrogated. In addition, the mixed lymphocyte reaction was significantly inhibited by rCD58. Moreover, cytotoxicity of human NK clones (CD2+CD3-) was inhibited by rCD58 similar to inhibition by CD58 mAbs. In contrast, rCD58 synergized with mitogenic CD2R mAbs in T cell triggering. These data demonstrate that rCD58 might serve as a biological immunomodulator which influences T cell adhesion and activation.

Amino Acid Sequence↗
PubMed1991

Clonal analysis of CD4+/CD8+ T cells in a patient with aplastic anemia.

T cell clones were established from peripheral blood of a patient with severe aplastic anemia. 8 of 18 individual clonal T cell populations stably coexpressed CD4 and CD8 molecules, a phenotype characteristic for thymocytes and a minor subpopulation of circulating T lymphocytes. Analysis of T cell receptor genes revealed identical rearrangements of T cell receptor beta chain genes, suggesting clonality of these T cells. CD4+/CD8+ T cells clones were found to be efficiently cytotoxic towards autologous lymphoblasts. Autocytotoxicity could be blocked by a CD3 MAb, a MAb specific for monomorphic MHC class II determinants, and particularly, by an MHC-DP-specific MAb, suggesting specificity for autologous DP molecules. Perhaps more important, CD4+/CD8+ T cell clones inhibited differentiation of autologous progenitor enriched bone marrow cells in vitro by a direct cell-mediated mechanism. These data suggest that circulating cytotoxic CD4+/CD8+ T cell clones specific for autologous MHC-DP determinants may be involved in hematopoietic failure in some cases of aplastic anemia.

Adult↗
PubMed1991

Hepatocellular expression of lymphocyte function-associated antigen 3 in chronic hepatitis.

T lymphocyte-mediated cytolytic immune reactions are considered a major cause of hepatocyte injury in chronic viral and autoimmune hepatitis. To further investigate local immune responses, we studied the expression of lymphocyte antigens and cell-cell interaction molecules known to be involved in effector-target cell interactions by light and electron microscopy in liver biopsy specimens from patients with chronic viral and autoimmune hepatitis. CD8+ lymphocytes were found to be the predominant population of cells in the inflammatory infiltrate in chronic hepatitis B and non-A, non-B hepatitis. In contrast, CD4+ cells constituted a comparably higher proportion of cells and were more numerous than CD8+ cells in chronic autoimmune hepatitis. In both viral and autoimmune hepatitis, a substantial portion of lymphocytes expressed activation antigens such as T11/3 (CD2R) and IL-2-R (CD25). Lymphocyte function-associated antigen-3 (CD58), which mediates lymphocyte adhesion and activation and is the natural ligand of the CD2/T11 lymphocyte surface receptor, could be demonstrated on endothelial cells and hepatocytes. Hepatocellular lymphocyte function-associated antigen-3 expression in chronic hepatitis showed membranous and cytoplasmic staining of hepatocytes and had a positive correlation with the degree of inflammatory activity. These results suggest that effector-target interactions between hepatocytes and lymphocytes mediated by the lymphocyte function-associated antigen-3/CD2 pathway play a role in chronic inflammatory liver disease. Possible functional consequences of this interaction include enhancement of antigen-specific immune reactions and antigen-independent mechanisms of T cell activation, which may contribute considerably to the degree of inflammatory activity and tissue damage in chronic hepatitis.

Antigens, Surface↗
PubMed1990

Association of CD2 and CD45 on human T lymphocytes.

At least two membrane receptors have been defined through which human T lymphocytes can be induced to proliferate and differentiate, namely the CD3-Ti antigen receptor complex and the CD2 molecule. Monoclonal antibodies directed at either CD2 or CD3 induce intracellular second messenger production and subsequent protein phosphorylation. On most human non-B lymphocytes, CD3-Ti and CD2 are coexpressed and seem to be functionally interrelated. But there are minor subpopulations in which these receptor systems can transduce signals despite a mutually exclusive expression, indicating that CD3-Ti and CD2 can act independently of each other. This view is supported by the finding that most monoclonal antibodies directed at the CD45 molecules are strongly co-mitogenic with CD2 but not CD3 monoclonal antibodies. As the intracytoplasmic domains of CD45 have tyrosine phosphatase activity these functional effects could be explained by a physical association between CD2 and CD45. Using chemical crosslinking techniques, we now show that CD45 is linked to CD2 on the surface of human T lymphocytes.

Antibodies, Monoclonal↗
PubMed1990

T cell receptor gene rearrangements of T lymphocytes infiltrating the liver in chronic active hepatitis B and primary biliary cirrhosis (PBC): oligoclonality of PBC-derived T cell clones.

Immunological events are involved in the pathophysiology of chronic active hepatitis as indicated from the accumulation of T lymphocytes at the site of tissue damage. We generated T cell clones from liver biopsies of 3 patients with chronic active hepatitis B and 2 patients with primary biliary cirrhosis. These T cell clones (n = 84) were analyzed by means of T cell receptor (TcR) beta gene rearrangements to determine whether the infiltrate consists of a polyclonal or oligoclonal T cell population. The vast majority (62 of 64) of T cell clones from three different patients with chronic active hepatitis B showed no identical rearrangements of the TcR beta chain genes. In marked contrast, in both patients with primary biliary cirrhosis, T cell clones established were of limited diversity. Thus 5 out of 10 and 2 out of 10 T cell clones from one patient and 3 out of 9 and 2 out of 9 T cell clones from the second patient, respectively, showed identical TcR beta gene rearrangements. These data suggest that a clonal dominance is characteristic for local T cell responses in autoimmune liver disease such as primary biliary cirrhosis whereas in virus-induced chronic active hepatitis T cell activation occurs polyclonally.

Adult↗