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M H Claesson

Publications and source records attributed to M H Claesson.

At least 91 records · Page 5Linked to original sources
PubMed1990

T-cell activation. III. Attempts to activate MHC class I-negative and class I-transfected EL4 T-lymphoma cells by immobilized anti-CD3 antibody.

The aim of this study was to examine whether the unresponsiveness of MHC class I-negative subclones of the EL4 thymoma to CD3 cross-linking can be restored by transfection of class I genes into the H-2-negative cells. Cell activation experiments with selected MHC class I-negative subclones and H-2b- and H-2Ld-positive transfectants showed that these cells are equally capable of secreting interleukin 2 (IL-2) after exposure to the phorbol ester phorbol 12-myristate 13-acetate (PMA) and ionomycin. In contrast, only the parental H-2-positive EL4 cells are capable of responding to treatment with immobilized anti-CD3 antibody with IL-2 secretion and IL-2 receptor expression. Measurements of intracellular free Ca2+ (Ca2+i) following anti-CD3 antibody-induced cross-linking of parental EL4 cells and H-2-negative and H-2b gene-transfected subclones showed that the parental cells and two of the class I transfectants, one H-2-positive and one H-2-negative, responded with a slow rise in Ca2+i, whereas one H-2-positive transfected cell clone was completely refractory to CD3 cross-linking. Modulation experiments using parental EL4 cells, H-2-negative subclones and H-2-positive transfectants demonstrated that the CD3 and class I molecules of these different cells are modulated to the same extent after exposure to specific antibodies. The present findings thus indicate that the unresponsiveness of H-2-negative EL4 subclone cells to CD3 cross-linking is not functionally associated with a lack of class I surface expression.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1990

Thymic epithelial cells. I. Expression of strong suppressive (veto) activity in mouse thymic epithelial cell cultures.

We show that thymic epithelial cells grown under serum-free conditions in a chemically defined culture medium can act as veto cells in vitro. The veto activity of thymic epithelial cells results in inactivation of specific alloreactive cytotoxic T-cell precursors at the clonal level. It is concluded that the epithelial stromal cells of the thymus, by acting as veto cells, may be responsible for the negative intrathymic selection of self-reactive thymocytes leading to elimination of the vast majority of immature thymic lymphocytes.

Animals↗
PubMed1990

Inhibitory effect of mycoplasma-released arginase. Activity in mixed-lymphocyte and tumour cell cultures.

Non-fermenting mycoplasma species deplete culture media for arginine through arginase activity linked to their arginine deiminase pathway, resulting in proliferation arrest and cell death in mycoplasma-contaminated cell cultures. The presence of only 2-3 Mycoplasma (M.) arginini-contaminated T cells in a one-way allogeneic mixed-lymphocyte culture (MLC) significantly inhibits development of cytotoxic T-cell activity. Likewise, strong degrees of inhibition are observed after addition of nanogram doses of M. arginini extracts (MAE) to MLC or cell proliferation cultures. M. arginini-induced cell inhibition can be reversed by addition of excess arginine to the culture medium. Antisera raised against non-fermenting, but not against fermenting, mycoplasma species block the inhibitory effect of MAE. SDS-PAGE separation of MAE disclosed a broad band at 60 kDa which contained arginase activity when assayed in MLC and cell proliferation culture. SDS-PAGE followed by western blotting and reaction with antisera raised against non-fermenting mycoplasma species demonstrated a band at 43 kDa common for these micro-organisms.

Animals↗
PubMed1989

Functional heterogeneity in allospecific cytotoxic T lymphocyte clones. III. Direct correlation between development of syngeneic cytotoxicity and loss of veto activity; implications for the mechanism of veto action.

Two veto active allospecific cytotoxic T-cell clones (CTL), 4A2 and 4B3, were studied for the development of autoreactivity. The 4A2 CTL became autoreactive within 6 days when cultured without appropriate allospecific stimulator cells, whereas the 4B3 CTL retained its alloreactivity without becoming autoreactive when cultured under these conditions. Simultaneously with the development of autoreactivity, the 4A2 CTL lost its veto activity. Limiting dilution cultures of normal allospecific 4A2 CTL cells and autoreactive 4A2 CTL cells and mixtures of both showed that the former CTL cells were capable of inhibiting clonal growth of the autoreactive CTL cells in a dose-dependent manner. We suggest that this growth inhibition reflects veto activity, i.e. cells capable of growing are inhibited by autorecognition of veto active allospecific 4A2 CTL cells. Taken together, the present results indicate that the existence of intraclonal down-regulation of potentially autoreactive cells is a normal feature of allospecific cytotoxic T-cell clones.

Animals↗
PubMed1989

T-cell activation. I. Evidence for a functional linkage between class I MHC antigens and the Tc-Ti complex.

This paper examines the possibility of a functional linkage between class I MHC molecules and the T-cell receptor complex for antigen (T3-Ti). A newly developed anti-CD3 antibody (500A2) was used as an activation signal for EL4 lymphoma cells and allospecific cytotoxic T-cell clones (CTL), and the production of IL-2/IL-2 receptor in EL4 cells and serine esterase in CTL was determined. Anti-CD3 antibody-induced activation of both EL4 and CTL cells was enhanced in the presence of immunologically cross-linked and immobilized anti-H-2 (class I) antibody reactive against the H-2 haplotype of the responding T cells. A number of H-2-negative and H-2-positive EL4 subclones were generated and tested for anti-CD3 antibody-induced IL-2/IL-2 receptor production. Although both H-2-positive and -negative subclones expressed CD3 antigen and produced IL-2 after activation with the phorbol ester TPA, only the H-2-positive cell clones produced IL-2 and expressed IL-2 receptor after anti-CD3 antibody induction. Our results are compatible with the existence of a functional linkage between the class I and the CD3 molecules on the surface of T cells.

Animals↗
PubMed1988

Studies of the MHC class I molecules of veto-active and veto-inactive lectin-stimulated spleen cell populations.

Mouse spleen cells activated for three days with ConA, but not with PHA and LPS, were found to possess strong veto activity. Thus, ConA-activated spleen cells were capable of preventing a cytotoxic T cell response generated in MLC against the H-2 haplotype of the ConA-activated cells. Radiolabelling and chemical cross-linking of veto-active and veto-inactive cells, followed by immunoprecipitation of H-2, class I antigens, and analyses of the precipitates by one and two dimensional SDS PAGE were performed. By these procedures we were unable to demonstrate qualitative and quantitative differences between precipitates of veto-active and veto-inactive cell populations.

Animals↗
PubMed1985

Functional heterogeneity in allospecific cytotoxic T lymphocyte clones. II. Development of syngeneic cytotoxicity in the absence of specific antigenic stimulation.

Two out of four long-term murine allospecific cytotoxic T lymphocyte (CTL) clones tested could develop high levels of cytotoxicity against syngeneic target cells when cultured under appropriate conditions. All CTL clones maintained strict allospecificity so long as they were cultured with both appropriate allogeneic stimulator cells and growth factor (supernatant from secondary mixed lymphocyte cultures). In two of the clones, syngeneic reactivity rapidly developed when the allogeneic stimulator cells were replaced with syngeneic or third party stimulator cells, and when the supernatant from EL4 thymoma cells stimulated with phorbol ester was used as growth factor. In addition to killing the appropriate allogeneic target, clones with syngeneic reactivity could kill both syngeneic C57BL/6 targets and H-2-congenic BALB.B targets but not third party unrelated targets, suggesting that the self structure recognized was coded for within the major histocompatibility complex. Such clones did not kill the natural killer (NK) target YAC. The results obtained from cold target inhibition and from subcloning at limiting dilution of clones with syngeneic reactivity suggested that both allogeneic and syngeneic reactivity could be expressed by the same individual cell in the CTL clone. The specificity for syngeneic H-2 as opposed to third party H-2 and NK-sensitive target cells, and the observation that both allospecific and syngeneic killing could be partially blocked by anti-Lyt-2 antibody treatment of the CTL, strongly suggested that different recognition structures are involved in CTL-mediated syngeneic cytotoxicity and NK cytotoxicity.

Animals↗
PubMed1977

B lymphocyte colony-forming cells in the SJL/J mouse.

Mercatoethanol-induced B lymphocyte cloning in semi-solid agar has been used to study lymphocyte colony formation by cells from the SJL/J mouse thymus. From the 3rd month of life, the SJL/J mouse thymus. From the 3rd month of life, the SJL thymus develops an increasing frequency of cells forming B lymphocyte colonies in agar. The peak frequency in 6- to 12-month-old mice was one colony per 1000 to 2000 cultured thymus cells. In contrast, 10 to 100 times lower frequencies were found in the thymus of five other inbred mouse strains. The rise in B lymphocyte colony-forming cells correlated well with the age-related rise in Ig-positive cells and approximately 50% of the colony cells reacted with anti-micron-serum indicating the B lymphocyte nature of the colony cells. Colony-forming cells from the thymus showed higher sensitivity than colony-forming spleen cells to cortisol and irradiation. Cell transfer experiments and thymus grafting suggested that the increased frequency of colony-forming cells in the thymus is caused by development of special thymus-seeking B lymphocytes in ageing SJL/J mice. Finally, B lymphocyte colony-forming cells were found to be more frequent in the thymus, spleen, and lymph nodes from healthy aged mice than in lymphoid organs from mice with spontaneous reticulum cell tumors.

Age Factors↗