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Biomedical subjects

M H Claësson

Publications and source records attributed to M H Claësson.

At least 19 recordsLinked to original sources
PubMed1998

Effect of the opioid methionine enkephalinamide on signal transduction in human T-lymphocytes.

T cell receptor (TCR/CD3) induced fluctuations in intracellular free ionizied calcium, [Ca2+]i, was analysed in the human T leukemia cell clone, Jurkat, cultured in the presence of the opioid methionine enkephalinamide (Met-Enk) in titrated concentrations (10[-7] to 10[-15] M) or saline (PBS). In the majority of individual experiments, the activation-induced fluctuations in [Ca2+]i were similar in cells cultured in the presence of Met-Enk and PBS, respectively. However, when all the experimental data from 101 separate TCR/CD3-activation experiments with Met-Enk were compared with the 67 separate control experiments, we found that a fraction (20-40%) of the individual sets of Met-Enk experiments responded significantly different when compared to PBS-controls. In this fraction of experiments the increase in [Ca2+]i after ligation of the TCR/CD3 complex was extremely slow compared to controls. Moreover, the levels of [Ca2+]i in this particular fraction were lower than control levels prior to ligation of the TCR/CD3 complex. The data support the idea that signal transduction in T cells can be influenced by endogenous opioid. The data therefore give credit to the evolving hypothesis of a functional relationship between the neuroendocrine system and the immune system.

Calcium↗
PubMed1997

Inflammatory bowel disease: potential therapeutic strategies.

This review deals with potential and possibly primary therapeutics that, through insight into the inflammatory cascade, result in more rational treatment principles replacing the classical therapy of inflammatory bowel disease (IBD), i.e. Crohn's disease (CD) and ulcerative colitis (UC). These new therapies might be useful for IBD patients, especially since the 'classical therapy' with agents like glucocorticoids, sulfasalazine, mesalazine, azathioprine, 6-mercaptopurine, cyclosporin and methotrexate is often only moderately effective and may have important side-effects. Controlled trials of the novel agents mentioned in this review have not yet been performed, however.

Animals↗
PubMed1994

Binding of human beta 2-microglobulin to murine EL4 thymoma cells upregulates MHC class I heavy-chain epitopes, inhibits IL-2 secretion and induces resistance to killing by natural killer cells.

A variety of murine tumor cell lines was studied for its binding of exogeneously added human beta 2-microglobulin (h beta 2m). Three T lymphomas and one IL-2-dependent T-cell line (HT-1) bound substantial amounts of h beta 2m, whereas P815 mastocytoma cells, an Abelson virus-infected pre-B cell line (ABLS-8), X63 B-lymphoma cells and YAC cells did not bind h beta 2m. In two of the T lymphomas, EL4 and BW5147, binding of h beta 2m led to an increase in major histocompatibility complex class I (MHC-I) heavy-chain epitope expression as measured by anti-H-2K/D antibody binding and FACS analysis. EL4 cells which had bound h beta 2m decreased their rate of constitutive IL-2 secretion and became resistant to activated natural killer (NK) cell killing. The present data suggest the binding of h beta 2m to mouse T cells leads to conformational changes of MHC-I heavy chains which influence both effector and target functions of the cell.

Animals↗
PubMed1993

Veto suppression: the peripheral way of T cell tolerization.

Cells with veto activity induce a state of tolerance in T cell precursors with specificity for antigen determinants expressed on the surface of the veto-active cell. This state of tolerance is not strictly defined, but results in altered responses to specific antigen, such as decreased proliferation, decreased development of cytotoxicity and secretion of interleukins, down-regulated ability to reject grafts and expression of T cell and IL-2 receptors. Both clonal anergy and clonal deletion has been shown to operate in vetoed T cells. Veto-induced tolerance can be established in vitro and in vivo for both MHC class I and II as well as minor histocompatibility antigens. The most powerful veto activity is present in mature activated cytotoxic CD8+ T cells, but other cells including noncytotoxic cells are also capable of acting as veto cells. Thus it appears that veto activity per se is not confined to a certain cellular entity, but rather reflects a constitutively expressed immunoregulatory capability inherent to a broad array of activated T cell and non-T cell categories with their own distinct functions not related to their eventual veto activity.

Animals↗
PubMed1993

T-cell activation. VI. Inhibitory and stimulatory effects of anti-major histocompatibility complex class I antibodies in allogeneic mixed lymphocyte culture.

Murine T splenocytes stimulated in primary allogeneic mixed lymphocyte culture (MLC) were incubated with soluble anti-major histocompatibility complex (MHC) class I monoclonal antibodies. These antibodies induced inhibition in the cytotoxicity of the responding population and this inhibition was not dependent on the domain on class I molecules recognized by the antibodies. Cross-reactivity of the antibodies between the responder and stimulating cell population caused a marked reduction in the inhibitory effect compared to systems where no such cross-reactivity was present. Saturating levels of the antibodies caused a reduction in generation of T-cell cytotoxicity, whereas low concentrations stimulated the same response. These results demonstrate that the MHC class I molecules of T cells are of significant importance in antigen-induced signal transduction.

Animals↗
PubMed1991

CD3+ T cells in severe combined immune deficiency (scid) mice. I. Transferred purified CD4+ T cells, but not CD8+ T cells are engrafted in the spleen of congenic scid mice.

Young (less than 3 months of age) and old (greater than 1 year of age) C.B-17 scid/scid mice were tested for the presence of immunoglobulin in serum and CD3+ T cells in spleen and peritoneal cavity. In all old severe combined immune deficiency (scid) mice tested we found detectable, but very variable levels of serum immunoglobulin as well as splenic and peritoneal CD3+ T cells comprising 3% to 10% of the nonfractionated cell populations of these organs (n = 10). In contrast, none of the analyzed young scid mice showed any evidence of peripheral lymphocytes. Low numbers (2 x 10(5) to 5 x 10(5) cells/mouse) of highly purified CD4+ cells from congenic C.B-17 or BALB/c donor mice were injected intravenously into young scid recipient mice. A CD4+ T cell population was clearly engrafted when transplanted scid mice were analyzed 8 to 13 weeks after T cell transfer: (a) a CD3+CD4+CD8- T cell population was detectable in the spleens of all recipient scid mice by flow microfluorometry analyses; (b) CD3+CD4+CD8 T cell lines could be grown out of these spleens in vitro; (c) the histological examination revealed evidence of lymphoid cell repopulation in the spleens of all transplanted scid mice and (d) transplanted CD4+ T cell populations could be serially transferred into secondary and tertiary recipient scid mice. These data indicate that scid mice can be constructed in which only the CD4+ T cell compartment is selectively reconstituted. In contrast to the successful engraftment of CD4+ T cell, highly purified congenic CD8+ T cells could not be engrafted into the spleen of scid mice.

Aging↗
PubMed1990

[Interleukin-2 based immunotherapy of cancer].

Interleukin-2 (IL-2) is produced by activated T-helper lymphocytes and stimulates both the antigen-specific and the non-specific immune defence. In vitro, IL-2 activated peripheral blood lymphocytes (LAK-cells) can lyse a broad spectrum of both NK-sensitive and NK-resistant tumour cell lines and IL-2 expanded tumour infiltrating lymphocytes (TIL) are, in certain cases, selectively able to lyse autologous tumour cells. In vivo, the mechanism behind the anti-tumour effect of IL-2 is unknown. Recombinant IL-2 has been available since 1984 and world-wide more than 3,000 patients have been treated. IL-2 has most frequently been administered in combination with either in vitro activated autologous effector cells and/or other cytokines or anti-cancer chemotherapeutic agents. The generation of autologous effector cells for patient treatment demands considerable resources and their contribution to the clinical effect is uncertain. The best responding tumour-types have been renal cell carcinoma and malignant melanoma with response rates up to 35% and 24%, respectively. IL-2 therapy is associated with considerable side-effects. The most serious are due to the development of a "capillary leak syndrome" with peripheral vasodilation and increased vascular permeability resulting in hypotension, oedema and organ-dysfunction. The majority of these side-effects are reversible with improvement within hours after terminating the IL-2 administration. It is concluded that IL-2 therapy is still experimental and it should be limited to treatment according to protocols in highly specialized clinical departments in a close cooperation with immunological laboratories.

Animals↗
PubMed1987

Veto cell H-2 antigens: veto cell activity is restricted by determinants encoded by K, D, and I MHC regions.

Responder cells from primary syngeneic and allogeneic one-way mixed-lymphocyte cultures (MLC) specifically inhibit the development of cytotoxic T lymphocytes (CTL) directed against the major histocompatibility complex (MHC) antigens of the MLC responder cells. This special kind of suppressor activity is known as veto suppression. Ia+ cells with veto activity obtained from H-2 recombinant mouse strains were shown to downregulate alloantigen (class II)-specific helper activity for class I-specific CTL development in a primary MLC provided that the veto cells expressed the same I-E alpha subregion as the MLC stimulator cells. The veto-induced suppression of allo-help was prevented by the addition of supernatant from concanavalin A-stimulated spleen cells (Con A-SN) and was inhibited considerably by very high amounts of recombinant interleukin-2 (IL-2). In the presence of Con A-SN, CTL precursors recognizing either the K end or the D end of the veto cell MHC were found to be inactivated. Thus, our results indicate that MLC responder cells include active veto cells expressing Ia region-encoded restriction elements for allospecific T helper cells, as well as K- or D-encoded restriction elements for allospecific T cytotoxic cells.

Animals↗
PubMed1987

Colony formation by subpopulations of human T lymphocytes. VI. Further studies on colony phenotype, function, and cloning efficiency.

Phytohemagglutinin (PHA)-induced colony formation in semisolid agar medium by human peripheral blood T lymphocytes showed an increasing cloning efficiency with decreasing numbers of cultured cells. Ninety percent of CD4+ cells (inducer/helper phenotype) and 20% of CD8+ cells (cytotoxic/suppressor phenotype) formed colonies when cultured at 10-200 cells/ml culture in the presence of sheep red blood cells (SRBC) and a source of interleukin-2 (IL-2). Probably all T-colony-forming cells, but none of the subsequent colony cells, expressed the Leu-8 antigen. The cloning efficiencies of FACS-sorted cells expressing the natural killer antigenic phenotypes Leu-7+ and CD16+ were found to be less than 1%. The costimulatory effect of red blood cells for colony formation was specific for SRBC and not observed in the presence of red cells obtained from seven other species including man. All T-lymphocyte colonies obtained from unseparated peripheral blood mononuclear cells expressed the CD25 antigen (IL-2 receptor) and colonies were always composed of either CD4+ or CD8+ cells. None of the colony cells expressed the Leu-8 or the CD16 antigens. By their specific morphology in agar culture the majority of colonies composed of CD4+ cells were easily recognized, but but approximately one-third of the CD4+ colonies could not be distinguished from colonies composed of CD8+ cells. On expansion of individual colonies in liquid subculture in the presence of interleukin-2, approximately 15% of the colonies developed natural killer (NK)-like cytotoxic activity, being capable of direct killing of K562 tumor cells. It is concluded that the present method for growing human T colonies exhibits the same cloning efficiency as the most efficient liquid culture systems. Individual T colonies are composed exclusively of T inducer/helper or T cytotoxic/suppressor cells, they are never of mixed phenotype, and they do not contain cells of natural killer phenotype. Regulatory mechanisms influencing colony formation are operating between and within the various subsets of T lymphocytes.

Adult↗
PubMed1987

Proteolytically modified human beta 2-microglobulin augments the specific cytotoxic activity in murine mixed lymphocyte culture.

A proteolytically modified form of beta 2-microglobulin (beta 2-m) present in the serum of patients suffering from autoimmune, immunodeficient diseases and cancer has been reported in the literature. In the present study we show that human beta 2-m as well as the proteolytically modified human form (M-beta 2-m) bind to murine lymphocytes expressing H-2 class I antigens; M-beta 2-m, when added at day 0 and 1 of culture in nanomolar concentrations to a one-way murine allogeneic mixed lymphocyte culture (MLC) augments the generation of specific cytotoxic T lymphocytes; M-beta 2-m increases the endogenous production of interleukin 2 in the MLC culture; monoclonal antibody which reacts with both the native beta 2-m and M-beta 2-m molecule blocks the augmentation of cytotoxic T lymphocyte production induced by M-beta 2-m; murine as well as human MLC responder cells can proteolytically modify native human beta 2-m; and the modifying activity of murine MLC responder cells was blocked in an intermediary step by an alloantibody, which reacts specifically with murine major histocompatibility complex, class I-associated beta 2-m. These findings suggest that the modification process is preceded by an association of human beta 2-m with the cell surface of the responder cells. Our data indicate that the modification of beta 2-m might reflect early events in allospecific responder cell activation.

Animals↗