Biomedical subjects

C Geisler

Publications and source records attributed to C Geisler.

At least 73 records · Page 4Linked to original sources

PubMed1993

Structure of the T-cell receptor in a Ti alpha beta, Ti gamma delta double positive T-cell line.

The multichain T-cell receptor is composed of at least six different polypeptide chains. The clonotypic Ti heterodimer (Ti alpha beta or Ti gamma delta) is non-covalently associated with the CD3 chains (CD3 gamma delta epsilon zeta). The exact number of subunits constituting the T-cell receptor is still not known. It has been suggested that each T-cell receptor contains two Ti dimers. To gain insight into the structure of the T-cell receptor we constructed a Ti alpha beta, Ti gamma delta double positive T-cell line which contained four functional Ti chains (Ti alpha, beta, gamma, and delta). The data demonstrated an absence of Ti dimers containing mixtures of chains other than the typical Ti alpha beta and Ti gamma delta combinations. Furthermore, by co-modulation experiments we demonstrated that the Ti alpha beta and the Ti gamma delta dimers were not expressed in the same T-cell receptor. Our data indicate that the T-cell receptor does not contain two Ti dimers.

Antibodies, Monoclonal↗

PubMed1993

T-cell activation. V. Anti-major histocompatibility complex class I antibody-induced activation and clonal abortion in Jurkat T-leukaemic cells.

We have studied activation-induced changes in intracellular calcium [Ca2+]i, interleukin-2 (IL-2) secretion, and clonal abortion of the human leukaemic T-cell line Jurkat and three T-cell receptor (TcR)/CD3 receptor negative clones deficient for the TcR alpha, TcR beta and CD3 gamma chains respectively, as well as three transfectant clones reconstituted with the appropriate TcR/CD3 cDNA. For activation, the cells were exposed to anti-TcR/CD3, anti-CD2 and anti-major histocompatibility complex (anti-MHC) class I monoclonal antibodies (mAb) respectively. Cellular activation by these mAb leading to an increased IL-2 secretion was preceded by a rise in [Ca2+]i and was relatively dependent on the expression of the a TcR/CD3 complex. In contrast, anti-MHC class I mAb-induced clonal abortion in Jurkat T cells may occur without previous fluctuations in [Ca2+]i and appeared to be independent of TcR/CD3 expression. The present observation suggest the existence of different secondary messenger systems operating in Jurkat cells following activation via the TcR/CD3, CD2 and the MHC class I pathways, respectively.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1993

Biosynthesis of Tcr-alpha, beta and Tcr-gamma, delta/CD3 complexes.

Jurkat J76 clone, LYON L12.37 clone and L12.37 cells transfected with J76-alpha cDNA or J76 Tcr-alpha mutated cDNA (J79) were analysed for membrane expression of Tcr/CD3 complex using WT31 mAb (Tcr-alpha, beta) or Tcr-delta 1 mAb (Tcr-gamma, delta): LYON cells express V beta 9 bearing Tcr-beta chains. J76 Tcr-alpha cDNA transfected LYON cells have intracellular Tcr-gamma, delta chains and J79 Tcr-alpha cDNA transfected LYON cells have intracellular Tcr-alpha (M), beta chains.

Amino Acid Sequence↗

PubMed1992

Structural mutations of C-domains in members of the Ig superfamily. Consequences for the interactions between the T cell antigen receptor and the zeta 2 homodimer.

Several molecules belonging to the Ig superfamily are expressed together with noncovalently associated subunits. This applies for membrane-bound IgM and IgD, some of the FcR, and the Ti dimers of the TCR. The interactions between members of the Ig superfamily and their associated subunits are still not fully understood. We locate critical amino acid residues for TCR assembly in the Ti-alpha and -beta extracellular C-domains. A point mutation (phenylalanine195----valine) in a highly conserved residue in the Ti-alpha chain of the Jurkat variant J79 was identified by DNA sequencing. This mutation did not prevent cytoplasmic association of Ti alpha beta and CD3 gamma delta epsilon, but abolished binding of the zeta 2 homodimer to the rest of the TCR. The consequences of this mutation for TCR assembly were confirmed by transfection of a site-directed mutagenized Ti-alpha chain into a Ti-alpha-deficient Jurkat variant. Computer model analysis showed that the Ti-alpha phenylalanine195 directly contributed to the beta-sheet facing away from the Ti-beta chain, indicating that it could be directly involved in the interactions between one or more of the CD3 chains or the zeta 2 dimer. Site-directed mutagenesis of the corresponding residue in the Ti-beta chain demonstrated that a phenylalanine216----valine substitution had similar effects on TCR assembly as the Ti-alpha mutation, whereas a phenylalanine216----histidine substitution allowed TCR assembly and expression. Whether the consequences for TCR assembly of the Ti-alpha and -beta mutations were due to any direct effects on the interaction between zeta and the Ti alpha beta dimer or to indirect effects are discussed.

Amino Acid Sequence↗

PubMed1992

Failure to synthesize the CD3-gamma chain. Consequences for T cell antigen receptor assembly, processing, and expression.

The TCR consists of the Ti alpha beta heterodimer and the associated CD3 chains, CD3 gamma delta epsilon zeta 2 or zeta eta. The structural relationships between the subunits of the Ti/CD3 complex are still not fully understood. To explore the roles of the individual CD3 chains for the assembly, intracellular processing, and expression of the TCR, mutants of the T cell line Jurkat were isolated. One variant, JGN, was found to produce all the Ti/CD3 components with the exception of CD3-gamma. The results indicate that: 1) the tetrameric form (Ti alpha beta-CD3 delta epsilon) of the Ti/CD3 complex is produced in the endoplasmic reticulum in the absence of CD3-gamma; 2) CD3-zeta does not associate with the Ti alpha beta-CD3 delta epsilon complex; 3) the Ti alpha beta-CD3 delta epsilon complex is not exported from the endoplasmic reticulum to the Golgi apparatus; and 4) CD3-gamma is required for cell surface expression of the Ti/CD3 complex. Transfection of the wild-type CD3-gamma gene into JGN reconstituted expression of functional Ti/CD3 complexes, and analysis of T cell lines producing different amounts of CD3-gamma indicated that CD3-gamma and CD3-delta competed for the binding to CD3-epsilon.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1992

T-cell receptor gamma delta-positive peripheral T-cell lymphomas presenting in the skin: a clinical, histological and immunophenotypic study.

Examination of biopsy samples from 62 patients with--or with suspected--cutaneous T-cell lymphoma (CTCL) revealed 2 cases in which the neoplastic cells were positive for the T-cell receptor (TCR) gamma delta complex. One patient had mycosis fungoides and 1 patient had a pleomorphic lymphoma of medium and large-cell type. Both cases showed aggressive courses with dissemination to internal organs and short survival times. The phenotypic examination showed that the neoplastic cells were positive with TCR delta 1, CD3, CD25, CD29, CD45R0 and CD54. No staining was seen with antibodies against framework determinants or variable regions on the TCR alpha beta heterodimer. Negative reactions were also seen with CD4, CD8, CD5, CD7, CD16, CD30 and CD57. It is concluded that rare CTCL express TCR gamma delta chains. These malignancies may originate from the TCR gamma delta-positive T cells seen in normal skin, and it is possible that their recognition may be important for clinical reasons.

Female↗

PubMed1991

Aberrations of chromosome 6 in 193 newly diagnosed untreated cases of chronic lymphocytic leukemia.

Aberrations of chromosome 6 were observed in 11 of 193 cases of chronic lymphocytic leukemia diagnosed January 1, 1984-November 1, 1988 and investigated cytogenetically within 30 days after diagnosis. The 6p was rearranged in 5 cases: 4 balanced and 1 unbalanced translocation. The 6q was involved in 6 cases: 4 deletions and 2 balanced translocations. Three of the del(6q) may be identical: del(6)(q13q27). In two cases there were no additional aberrations. Aberrations of chromosome 6 correlated significantly with an advanced clinical stage, diffuse pattern of bone marrow infiltration, and increased SmIgM-fluorescence intensity. All these factors are associated with poor prognosis. Although the number of cases with 6q aberrations is still too small and the observation period too short to show significant influence on survival, the presence of 6q aberrations at diagnosis may prove useful in delineating a subtype of chronic lymphocytic leukemia with poor prognosis.

Bone Marrow↗

PubMed1991

HIV-associated lymphoma: histopathology and association with Epstein-Barr virus genome related to clinical, immunological and prognostic features.

All 51 cases of HIV-related malignant lymphoma in Denmark diagnosed from 1983 to 1989 were reviewed. There were 12 Burkitt-type lymphomas, 30 immunoblast-rich lymphomas and 9 other lymphomas. Patients with immunoblast-rich lymphomas had significantly lower CD4 cell counts (median 60 vs. 188 x 10(6)/l, P less than 0.05), and more often a history of previous AIDS-defining illnesses (50% vs. 0%, P less than 0.005), compared with patients with Burkitt-type lymphomas. Epstein-Barr virus (EBV) DNA was demonstrated in 14 of 19 immunoblast-rich tumours, and in 2 of 7 Burkitt-type lymphomas (P = 0.10). Compared with EBV DNA-negative tumours EBV DNA-positive tumours were associated with lower CD4 cell counts (median 39 vs. 188 x 10(6)/l, P = 0.01). It is concluded that two main types of HIV-related malignant lymphoma exist. One is associated with severe immunosuppression, is often of immunoblast-rich morphology, and may be linked to EBV, whereas the other may occur in the absence of immunosuppression, is often of Burkitt-type morphology, and is probably not linked to EBV. In addition to these two main types, other non-Hodgkin lymphomas and Hodgkin's disease do occur.

Adult↗

PubMed1991

Phenotypical and functional characterization of double-negative (CD4-CD8-) alpha beta T-cell receptor positive cells from an immunodeficient patient.

We have characterized CD4-CD8- double-negative (DN) alpha beta TCR+ T cells from a patient with immunodeficiency, lymphocytosis, lymphadenopathy, and hepatosplenomegaly. The majority of peripheral blood lymphocytes were DN alpha beta TCR+ T cells as evaluated by FACS and biochemical analysis. The DN T cells showed the following phenotype: alpha beta TCR+, gamma delta TCR-, CD2+, CD3+, CD4-, CD5+, CD7-, CD8-, CD16-, CD25-, CD26-, CD28+, CD45RO-, CD45RA+, CD57+, and HLA-DR+. Both southern blot analysis of TCR genes and FACS analysis applying a panel of V beta and V alpha monoclonal antibodies (MoAbs) indicated a polyclonal T-cell expansion. Thymic biopsy showed normal histology, whereas lymph node biopsy samples showed altered histological and immunohistological patterns with markedly expanded paracortical areas containing the DN T cells of the same phenotype as found in peripheral blood T cells. In functional studies, the DN T cells showed a profoundly reduced proliferative response upon stimulation with mitogens as well as MoAbs against the TCR/CD3 complex, CD2, and CD28, respectively. Addition of exogenous interleukin-2 (IL-2) only minimally augmented the proliferative response. In contrast, the addition of a combination of Ca2+ ionophore and phorbol 12-myristate 13-acetate (PMA) restored the proliferative response of the DN T cells to almost normal levels. This observation strongly suggests that the protein kinase C activity of the DN T cells was intact, but that the normal mechanism for transmembrane signal transduction was impaired in these unusual DN T cells.

Antigens, CD↗

PubMed1990

Association of the human CD3-zeta chain with the alpha beta-T cell receptor/CD3 complex. Clues from a T cell variant with a mutated T cell receptor-alpha chain.

The TCR for Ag, on the majority of human T cells, is a disulfide-linked heterodimer composed of TCR-alpha and -beta chains noncovalently associated with the monomorphic CD3 complex composed of the CD3-gamma, -delta, -epsilon, and -zeta chains. The interactions involved in the assembly of the various components of this multimeric protein complex are not fully understood. In this report, a variant of the human leukemic T cell line Jurkat that synthesized all of the known components of the TCR/CD3 complex but fails to express the TCR/CD3 complex at the cell surface is further characterized. This variant, J79, has a mutated TCR-alpha chain that does not affect the assembly of the pentameric form (TCR-alpha beta-CD3-gamma delta epsilon) of the TCR/CD3 complex but inhibits the assembly of the CD3-zeta homodimer with the rest of the complex (TCR-alpha beta-CD3-gamma delta epsilon----TCR-alpha beta-CD3-gamma delta epsilon zeta 2). Transfecting a wild-type TCR-alpha gene into J79 reconstituted expression of a complete functionally competent TCR/CD3 complex at the cell surface. The results indicate that the TCR-alpha chain plays a crucial role in the assembly of the CD3-zeta homodimer with the pentameric form of the TCR/CD3 complex.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1990

T cell activation. II. Activation of human T lymphoma cells by cross-linking of their MHC class I antigens.

The present work demonstrates that antibody-induced cross-linking of MHC class I antigens on Jurkat T lymphoma cells leads to a rise in intracellular calcium (Cai2+) and, in the presence of phorbol ester (PMA), to IL-2 production and IL-2 receptor expression. The rise in Cai2+ exhibited a profile very different from that obtained after anti-CD3 antibody-induced activation suggesting that activation signals are transduced differently after binding of anti-CD3 antibody and class I cross-linking, respectively. However, when Cai2+ was examined in individual Jurkat cells by means of a digital image processing system no differences were observed after cross-linking with anti-CD3 and anti-MHC class I antibodies, respectively. Two CD3-negative mutant lymphoma lines were nearly totally refractory to class I cross-linking. Taken together our results may indicate the existence of a functional linkage between the T cell receptor complex and MHC class I molecules.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1990

Cellular and molecular characteristics of transformed T cells from an antigen-specific T-cell line.

An antigen-specific T-cell line which transforms into T-lymphoma cells in vitro but apparently not in vivo is described. Membrane markers, tumorigenicity and T-cell receptor (TcR) V alpha and V beta-gene usage of the in vitro transformed T-cell line were analysed to investigate whether the transformation event was poly-, oligo-, or monoclonal. The results indicate that the T lymphoma has no chromosome abnormalities, contains no tumour-inducing virus, can induce clone-specific immunity, and is oligoclonal with respect to TcR V alpha and V beta expression. The nature of the transformation event and clinical application of vaccination against T lymphomas is discussed. In addition, the expressed TcR V alpha and V beta repertoire of Con A T blasts was apparently not affected by the Igh-l or the MHC haplotype, as investigated in Igh-l and MHC congeneic C57Bl mice.

Animals↗

PubMed1990

Accessory signals in T-T cell interactions between antigen- and alloantigen-specific, human memory T cells generated in vitro.

The potential of activated HLA class II-positive T cells as antigen-/alloantigen-presenting cells remains controversial. In our model system we use in vitro-primed, HLA class II-specific T cells of the memory T-cell phenotype, CD4+, CD29+ (4B4+), and CD45RO+ (UCHL-1). We have previously shown that alloactivated, HLA class II-positive T cells (Ta) are unable to stimulate proliferative responses in naive and primed allospecific T cells when 'back-stimulation' is avoided. The explanation of this feature of Ta is unknown, but it is due neither to suppression nor to insufficient HLA class II expression. Accordingly, we investigated the possibility that Ta have a deficient expression of accessory signals critical for the induction of proliferative T-cell responses. We found that (1) non-mitogenic concentrations of phorbol myristate acetate (PMA) in combination with either rIL-4, a CD28-reactive MoAb (Kolt-2), or a calcium ionophore (A23187) enabled Ta to elicit alloantigen-specific memory T-cell responses and to present purified protein derivative (PPD) to PPD-specific T-cell lines. The addition of irradiated, Epstein-Barr virus-transformed B-cell lines (EBV-LCL) (but not their supernatants) had a similar but less pronounced effect; (2) MoAb directed against HLA class II, CD25 (IL-2R), CD2, CD4, CD11a (LFA-1), or CD45RO molecules inhibited these responses; (3) PMA was required within the first hour of culture in order to induce optimal alloantigen-specific T-cell activation, while rIL-4 was fully effective when added after 20-44 h of culture; (4) incubation for 20 h of Ta with rIL-4 plus PMA markedly up-regulated CD54 expression on the Ta, and IL-4 seemed to potentiate the effect of PMA on the CD54 expression. In conclusion, the present data indicate that the inability of Ta to elicit (allo)antigen-specific, proliferative T-cell response is due to a lack of critical accessory signals. Up-regulation of CD54 was not sufficient for Ta to stimulate proliferative responses. Neither cytokines (IL-1, IL-6, and others) nor triggering of CD2 epitopes (T11.2 and T11.3) by soluble MoAb or solid phase support by MoAb against a number of accessory molecules provided the necessary signals. Thus, our data indicate that other, as yet unknown, signalling pathways play a key role in antigen- and alloantigen-specific T-T interactions. These pathways still need to be identified.

Antibodies, Monoclonal↗

PubMed1990

Transmembrane signalling via HLA-DR molecules on T cells from a Sezary T-cell leukaemia line.

The human Sezary T-cell leukaemia line, HUT.78, represents a population of activated T cells, i.e. they are HLA-DR+ and IL-2R+. We have analysed the capacity of HUT.78 cells (1) to stimulate HLA-DR-specific T-cell lines or clones and (2) to be induced to synthesize IL-2 by anti-HLA-DR monoclonal antibodies. The results of our experiments show that HLA-DR molecules on HUT.78 cells can stimulate at least one HLA-DR-specific T-cell clone and can act as transmembrane signal transmitters.

Antibodies, Monoclonal↗

PubMed1989

Assembly, intracellular processing, and expression at the cell surface of the human alpha beta T cell receptor/CD3 complex. Function of the CD3-zeta chain.

The TCR/CD3 complex is a multimeric protein complex composed of a minimum of seven transmembrane chains (TCR alpha beta-CD3 gamma delta epsilon zeta 2). Whereas earlier studies have demonstrated that both the TCR-alpha and -beta chains are required for the cell surface expression of the TCR/CD3 complex, the role of the CD3 chains for the TCR/CD3 expression have not been experimentally addressed in human T cells. In this study the function of the CD3-zeta chain for the assembly, intracellular processing, and expression of the TCR/CD3 complex in the human leukemic T cell line Jurkat was investigated. The results indicate that: 1) CD3-zeta is required for the cell surface expression of the TCR/CD3 complex; 2) the pentameric form (TCR alpha beta-CD3 gamma delta epsilon) of the TCR/CD3 complex and single TCR chains associated with CD3 (TCR alpha-CD3 gamma delta epsilon and TCR beta-CD3 gamma delta epsilon) are produced in the endoplasmic reticulum in the absence of CD3-zeta; 3) the CD3-zeta does not associate with TCR alpha-CD3 gamma delta epsilon or TCR beta-CD3 gamma delta epsilon complexes; 4) CD3-zeta associate with the pentameric form of the TCR/CD3 complex in the endoplasmic reticulum to form the heptameric complex (TCR alpha beta-CD3 gamma delta epsilon----TCR alpha beta-CD3 gamma delta epsilon 2); and 5) CD3-zeta is required for the export of the TCR/CD3 complex from the endoplasmic reticulum to the Golgi apparatus for subsequent processing.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1989

Fractionation of T cell subsets on Ig anti-Ig columns: isolation of helper T cells from nonresponder mice, demonstration of antigen-specific T suppressor cells, and selection of CD-3 negative variants of Jurkat T cells.

In the present experiments we have explored the possibilities of a modified immunoadsorbent technique to select for (1) mutagenized T cell receptor (Tcr) negative variants of Jurkat T lymphoma cells and (2) purified CD-4+ or CD-8+ T lymphocytes. The basic principle was to make large numbers of immunoglobulin (Ig) negative T cells Ig+ by T cell subset-specific monoclonal antibodies (mAb), and to select such cells on Ig anti-Ig columns. Our results demonstrated that Thy-1+, Fc receptor positive, antigen-specific T cells regulate the immune response in mice nonresponders to pork insulin, and the "autologous" mixed lymphocyte reaction. In addition, the immunoadsorbent method very efficiently selects Tcr/CD-3- variants from mutagenized Jurkat cell populations incubated with anti-CD3 mAb. The described method is easy and quick and can fractionate large numbers of cells; it is the "poor-man's cell sorter." The most important finding is the demonstration of antigen-specific Thy-1+, CD-8+, and Fc receptor+ T suppressor cell that apparently react with antigen in a non-major histocompatibility complex-restricted manner.

Animals↗

PubMed1989

Alloactivated HLA class II-positive T-cell lines induce IL-2 reactivity but lack accessory cell function in mixed leukocyte culture.

Recently, much interest has focused on the role of HLA class II antigens in T cell-T cell interactions. We have studied the stimulatory capability in the primary mixed leukocyte reaction and the primed lymphocyte reaction of 11 alloactivated, HLA-DR- or -DP-reactive CD4-positive T-cell lines (Ta). From 70 to 90% of the Ta were HLA class II-positive as judged by the reactions with HLA class II-reactive monoclonal antibodies, and the Ta carried the DR allospecificities of the original T-cell donor when typed in the microcytotoxic test using DR-specific alloantisera. Neither irradiated nor nonirradiated Ta stimulated primed lymphocytes directed against the relevant HLA class II antigens on the Ta. Interferon-gamma, recombinant interleukin 1, phorbol myristate acetate, calcium ionophore, and adherent cells had no effect on the stimulatory capability of Ta. The ability of irradiated Ta to stimulate in the primary mixed leukocyte reaction (median counts per minute (cpm) 5.5 x 10(3] was significantly lower than that of peripheral blood mononuclear cells (cpm: 44.0 x 10(3]. The stimulation by Ta was almost only seen when the Ta were specifically directed against the class II antigens of the responder peripheral blood mononuclear cells (i.e., in combinations with "backstimulation") (median cpm: 21,000). In mixed leukocyte reaction combinations without backstimulation, significantly weaker reactions were seen (median cpm: 1,000). This observation may explain previous controversies concerning the stimulatory capacity of Ta. Recombinant interleukin 2 significantly enhanced the very low mixed leukocyte culture responses induced by class II-incompatible Ta in combinations without backstimulation but had no significant effect on cultures with Ta autologous to the responder peripheral blood mononuclear cells. Thus, allogeneic class II-positive Ta can induce interleukin 2 responsiveness but lack accessory cell function(s) necessary for the induction of interleukin 2 production in primed and unprimed T cells.

Antibodies, Monoclonal↗

PubMed1989

Specific depletion of mature T lymphocytes from human bone marrow.

An effective method for specific depletion of mature T lymphocytes from human bone marrow mononuclear cells (BMMC) with preservation of prethymic T cells and natural killer (NK) cells is presented. The BMMC were incubated with F101.01, a monoclonal antibody recognizing an epitope of the T-cell receptor-CD3 complex, and subsequently with immunomagnetic beads. Flow cytometric analysis demonstrated that mature T cells were efficiently depleted and that NK cells and prethymic T cells were preserved in the BMMC. Furthermore, T cell-mediated immune reaction as measured by thymidine incorporation after stimulation with phytohaemagglutinin was abolished, whereas NK activity as measured by 51Cr release using K562 as target cells was preserved. Recovery of colony-forming units of granulocyte-macrophages was 60-70%.

Bone Marrow↗