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Biomedical subjects

H Wekerle

Publications and source records attributed to H Wekerle.

At least 19 recordsLinked to original sources
PubMed1992

Human myoblasts as antigen-presenting cells.

Human myoblasts, cultured from muscle and purified to greater than 95%, were investigated for their capacity to act as facultative APC. The myoblasts reacted with antidesmin mAb and had the capacity to fuse into multinucleated myotubes in appropriate medium. The expression of HLA class I, HLA-DR, HLA-DP, HLA-DQ, intercellular adhesion molecule-1 (ICAM-1/CD54), lymphocyte function-associated (LFA) molecules LFA-1 (CD11a/CD18), LFA-2 (CD2), and LFA-3 (CD58) was investigated by FACS analysis before and after induction for various times with human rIFN-gamma, TNF-alpha, or both. Without cytokine induction, myoblasts expressed only HLA-class I and LFA-3. IFN-gamma alone or in combination with TNF-alpha induced the expression of HLA-DR and ICAM-1 reaching a plateau after 48 h, followed by HLA-DP and even later HLA-DQ. TNF-alpha alone induced only ICAM-1. The functional capacity of myoblasts to present Ag to CD4+ T cells was investigated using autologous T cell lines specific for tuberculin, tetanus toxoid, and human myelin basic protein. Noninduced myoblasts or myoblasts treated with TNF-alpha alone could not present any of these Ag to the T cells. However, myoblasts treated with IFN-gamma induced Ag-specific proliferation. In the presence of relevant Ag, myoblasts were killed by the T cells as observed by microscopy and measured by 51Cr release. Ag-specific T cell proliferation and myoblast killing was inhibited in the presence of anti-DR mAb. These results suggest that human myoblasts may act as facultative APC during local immune reactions in muscle.

Antigen-Presenting Cells↗
PubMed1992

Diversity of T cell receptor alpha and beta chain genes expressed by human T cells specific for similar myelin basic protein peptide/major histocompatibility complexes.

T cell receptor (TcR) alpha and beta nucleotide sequences involved in the human autoreactivity to myelin basic protein (MBP) were studied by screening cDNA libraries derived from 11 independent T lymphocyte clones (TCC) established from multiple sclerosis patients and healthy donors. The TCC with defined MBP peptide specificity and HLA-DR restriction expressed multiple TcR. Even TCC recognizing the same human MBP peptide [amino acids (aa) 139-153] in identical or very similar HLA-DR context expressed diverse TcR. Two TCC which recognized peptide aa 139-153 equally well in the context of both HLA-DR2a and -DR1 molecules used distinct TcR alpha but identical beta chains. The knowledge of TcR beta and TcR alpha chain sequences of human MBP-specific T cells will allow studies correlating structure and function of TcR and their targets in MBP autoreactivity. This may have an impact on the development of immunotherapies in multiple sclerosis.

Amino Acid Sequence↗
PubMed1992

Immune regulation in self tolerance: functional elimination of a self-reactive, counterregulatory CD8+ T lymphocyte circuit by neonatal transfer of encephalitogenic CD4+ T cells lines.

Transfer of encephalitogenic, CD4+ T lymphocyte lines into syngeneic adult Lewis rats not only leads to the development of experimental autoimmune encephalomyelitis (EAE), but, in addition, to the expansion of counterregulatory, CD8+ T lymphocyte clones which are able to lyse specifically the encephalitogenic T cells in vitro and to neutralize their encephalitogenic capacity in vivo. In striking contrast, in neonatal rats, which still lack myelin (autoantigens), injection of the same encephalitogenic lines neither mediates EAE, nor confers protection in later life against the myelin-specific T cells. In fact, this treatment results in the life-long functional elimination of counterregulatory, clonotypic CD8+ T lymphocytes, which cannot even be reinduced by repeated injections of the relevant CD4+ T line. These data seem to point to a self-protective T cell control mechanism which is developed within the immune system prior to, and thus independent of the appearance of the appropriate self antigen.

Animals↗
PubMed1992

Interaction between oligodendroglia and immune cells: mitogenic effect of an oligodendrocyte precursor cell line on syngeneic T lymphocytes.

We analyzed cellular interactions between T lymphocytes and a recently established immortal glial line, L3 that retains several properties of immature oligodendrocytes (Aloisi et al., J Neurosci Res 27:16-24, 1990). L3 oligodendrocytes (L3-OL) cannot be induced to express class II antigens, nor do they specifically present antigen to syngeneic specific T lymphocyte. However, L3-OL strongly enhance the proliferation of freshly activated, interleukin-2(IL-2)-dependent T-line lymphocytes and concanavalin A (ConA)-activated lymphoblasts, irrespective of their antigen specificity or surface phenotype (CD4+ or CD8+). Resting and some activated T cells were susceptible to the mitogenic effect of L3-OL only in the presence of exogenous IL-2, not of other cytokines. The mitogenic effect of L3-OL did not depend on cell viability. It was observed in paraformaldehyde-fixed L3-OL cells and in membrane preparations, but not in culture supernatant. Neither intact L3-OL cells nor membrane preparations had direct IL-2 activity. The conclusion that the mitogenic effect of L3-OL cells is exerted by membrane structures acting as a costimulatory factor(s) of IL-2 is supported by the finding that it is largely blocked by a monoclonal anti-IL-2 receptor antibody. The effect is distinct from membrane-bound IL-1, membrane-bound tumor necrosis factor-alpha (TNF-alpha), IL-3, or IL-6 and cannot be reconstituted by these cytokines.

Animals↗
PubMed1992

Delineation of tissue damage mechanisms in experimental autoimmune encephalomyelitis (EAE). I. Cell detachment and lysis induced by encephalitogenic CD4+ T lymphocytes.

Myelin basic protein (MBP) reactive CD4+ T lymphocytes, capable of inducing experimental autoimmune encephalomyelitis (EAE), were examined for their ability to damage target cells of central nervous system (CNS) origin. Damage was assessed by monitoring detachment of adherent astrocytes from substratum and astrocyte lysis. MBP-specific, but non-encephalitogenic CD4+ T cells mediated astrocyte detachment but not lysis. However, encephalitogenic CD4+ T cell lines were more efficient in causing astrocyte detachment and could also cause astrocyte lysis. The detachment and lytic activities of the MBP-reactive T cell lines tested were often independent of the presence of specific antigen, and were not restricted to syngeneic major histocompatibility (MHC) antigens. MBP often augmented the detaching and, if lytic, lytic activities of these T cells. The encephalitogenic CD4+ T cells also detached and lysed allogeneic 'bystander' fibroblasts in the presence of unlabelled syngeneic astrocytes, suggesting the involvement of a soluble mediator(s). Although MBP is essential for the initiation of EAE, the presence of MBP on cells of CNS origin, such as astrocytes and oligodendrocytes, does not appear to be necessary for their damage by MBP-specific CD4+ T cells. Immune CD4+ T cells, which penetrate the CNS, may disorganize brain tissue structure by lysing astrocytes directly and by damaging other brain cells indirectly by soluble mediators. Thus cellular detachment, in addition to cell lysis, mediated by MBP-specific CD4+ cells may contribute to EAE pathogenesis.

Animals↗
PubMed1979

Autoimmune interaction measured in a postlabelling microcytostasis assay.

A postlabelling microcytostasis assay was developed to assess primary immune interaction between normal rat lymphocytes and autologous testis cells. In this vitro model of experimental autoimmune orchitis (EAO) unprimed T cells respond to a Sertoli-like subpopulation of testis cells during a 4 day culture period. The T effector cells exert a cytostatic effect on the monolayer-forming target cells. The number of remaining target cells, which inversely correlates with the intensity of the autoimmune reaction, is quantified by 51Cr incorporation. The assay is performed in multiple well plastic plates which allow rapid harvesting by cutting off the bottoms of each well. The attached labelled target cells are directly measured on the bottoms without any further transfer step. The method is adapted for the EAO model but may be useful to study primary T cell interaction with any other monolayer-forming target cells.

Animals↗
PubMed1978

Immunological T-cell memory in the in vitro-induced experimental autoimmune orchitis: specificity of the reaction and tissue distribution of the autoantigens.

Immunological memory has been induced in vitro against testicular autoantigens by priming normal rat T lymphocytes against autologous testis cells, and by permitting the isolated blast cells to revert back to small secondary lymphocytes (secondary EAO cells) in the absence of the priming antigen. The secondary EAO cells vigorously respond in a secondary response when reconfronted with syngeneic testis or lymphoid cells. Their responsiveness to nonself stimulator cells is, however, reduced. Secondary cells derived from concanavalin A-stimulated blasts, do not show that pattern of specificity. The specificity of the secondary EAO cells is definite, and cannot be affected by further culture on allogeneic fibroblasts, which are antigenic for unprimed T lymphocytes. At least part of the autoantigens are determined by the major histocompatibility gene complex (MHC). Factors provided by the culture system do not appear to determine the specificity of this reaction. Only minor cell populations can restimulate secondary EAO cells. One of these populations is presumably phage-like cells within the lymphoid populations can elicit a secondary EAO response. Thus, the autoantigens relevant in the secondary EAO response are either MHC antigens restricted to these testicular and lymphoid subpopulations, or MHC antigens recognized in conjunction with organ-specific non-MHC determinants.

Animals↗
PubMed1978

In vitro induction of experimental autoimmune orchitis: characterization of a primary T lymhocyte response against testicular self antigens.

Lymphocytes from normal, young adult rats were autosensitized in vitro against trypsin-dissociated autologous testis cells. The autoimmune response had been assayed both by determination of the lymphocyte proliferation, using a (3H)thymidine incorporation test, as well as by determination of their specific cytostatic activity against monolayer-forming testis cells which was measured in a terminal 51Cr uptake assay. The actively responding cells in this system are T lymphocytes. Non-T cells can exert additional, non-specific cytostasis. The immune specificity of the in vitro experimental autoimmune orchitis (EAO) has been demonstrated on two levels. First, the responding T lymphocytes were found to specifically adhere around cells from one particular testis subpopulation which morphologically resemble Sertoli cells. The rosetting lymphocytes respond only to testicular self antigen, but not to allogeneic lymphocytes. Second, specificity to the effector T lymphocytes was revealed in transfer experiments. Autosensitized EAO effector T cells cytostatically affected only major histocompatibility gene complex (MHC)-compatible testis cells. Their reactivity against MHC-different testis cells or MHC-compatible nontesticular fibroblasts was significantly decreased which suggests both tissue as well as MHC specificity of the EAO response.

Animals↗
PubMed1978

Intrathymic pathogenesis of myasthenia gravis: transient expression of acetylcholine receptors on thymus-derived myogenic cells.

Differentiation of myogenic stem cells from undifferentiated thymic stem cells is thought to play a critical role in the pathogenesis of myasthenia gravis. The expression of membrane acetylcholine receptor (AChR) on the membranes of developing muscle clones in cultures of murine thymus reticulum was followed and found to be transient. AChR are first expressed shortly after fusion of myotubes. In subsequent stages of myogenic development, the density of homogenously distributed AChR is strongly increased, and, in addition, concentrated "hot spot" AChR areas appear. During further maturation, membrane AChR are lost. Highly mature myotubes (3 months in culture) lack substantial amounts of homogenous AChR, as well as hot spots.

Acetylcholine↗
PubMed1977

Intrathymic pathogenesis and dual genetic control of myasthenia gravis.

We propose a two-step model for the pathogenesis of myasthenia gravis. In the first step, primitive intrathymic stem-cells are induced by abnormal stimuli to differentiate to (abnormal?) myogenic cells. In the second step, immunocompetent T lymphocytes start an autoimmune reaction against these newly differentiated myogenic cells. The clinical stage is reached when autosensitised effector T lymphocytes leave the thymus and either infiltrate the synaptic spaces of peripheral muscles or participate in the formation of autoantibodies, causing the neuromuscular symptoms. At two points the pathogenesis is under genetic control--the first at the differentiation of the stem-cells to myogenic cells and the second at the immune responsiveness of the lymphocytes to these atypical intrathymic muscle cells.

Animals↗
PubMed1977

Recognition of alterations induced by early vaccinia surface antigens and dependence of virus-specific lysis on H-2 antigen concentration on target cells.

Specific recognition of antigens by cytolytic T lymphocytes sensitized to vaccinia virus was tested by monolayer adsorption. Adsorption was possible only on monolayers also expressing syngenic H-2 as viral antigens present during the sensitization phase. Vaccinia-virus-infected target cells were subjected to papain and neuraminidase treatment. H-2 antigenic determinants could be removed by papain treatment. Due to virus-specific inhibition of host-cell protein synthesis, reexpression of H-2 antigenic determinants did not take place, but viral surface antigens were resynthesized. Susceptibility of target cells to T-cell-mediated lysis was decreased after papain treatment. Substrains of vaccinia virus were used in order to define the minimal changes induced by vaccinia virus necessary for T-cell sensitization in vivo and target-cell lysis in vitro. When the immune response to a conditioanl lethal mutant strain of vaccinia virus was investigated, it could be demonstrated that expression of early surface antigens is sufficient for induction of the cellular immune reactions. These data were confirmed by inhibition studies with virus-specific antisera.

Animals↗
PubMed1976

Thymus-derived striated muscle clones. An ultrastructural analysis of cell differentiation.

Myogenic clones can be induced in thymus reticulum cultures from adult mice. We investigated the differentiation and maturation of myogenic cells by combined ultrathin section and freeze etching analyses. New insights into the development of cell membranes and cytoplasmic organelles will be discussed in the light of previous investigations of embryonic muscle cell cultures.

Animals↗