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Biomedical subjects

E Claassen

Publications and source records attributed to E Claassen.

At least 37 records · Page 2Linked to original sources
PubMed1997

Role of macrophages during Theiler's virus infection.

Theiler's virus, a murine picornavirus, causes a persistent infection of the central nervous system with chronic inflammation and primary demyelination. We examined the nature of infected cells at different times postinoculation (p.i.) with a combined immunocytochemistry-in situ hybridization assay. The virus was found in the gray matter of the brain, mostly in neurons, during the first week p.i. During the following weeks, the virus was present in the spinal cord, first in the gray and white matter, then exclusively in the white matter. Approximately 10% of infected cells were astrocytes at any time during the study. Infected oligodendrocytes were first noticed on day 14 p.i. and amounted to approximately 6% of infected cells. The number of infected macrophages increased with time and reached a plateau by day 21 p.i., when at least 45% of infected cells were macrophages. The role of blood-borne macrophages during infection was studied by depleting them with mannosylated liposomes containing dichloromethylene diphosphonate. The virus did not persist in the majority of the mice treated with liposomes. These mice showed only minimal mononuclear cell infiltration and no demyelination.

Animals↗
PubMed1996

CD40-CD40 ligand interactions in experimental allergic encephalomyelitis and multiple sclerosis.

We investigated the role of CD40-CD40 ligand (CD40L) interactions in multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE). Activated helper T cells expressing CD40L (gp39) surface protein were found in MS patient brain sections, but not in brain tissue sections of normal controls or patients with other neurological disease. CD40L-positive cells were co-localized with CD40-bearing cells in active lesions (perivascular infiltrates). Most of these CD40-bearing cells proved to be of the monocytic lineage (macrophages or microglial cells), and relatively few were B cells. To functionally evaluate CD40-CD40L interactions, EAE was elicited in mice by means of proteolipid-peptide immunization. Treatment with anti-CD40L monoclonal antibody completely prevented the development of disease. Furthermore, administration of anti-CD40L monoclonal antibody, even after disease onset, shortly before maximum disability score was reached led to dramatic disease reduction. The presence of helper T cells expressing CD40L in brain tissue of MS patients and EAE animals, together with the functional evidence provided by successful experimental prevention and therapy in an animal model, indicates that blockade of CD40-CD40L-mediated cellular interactions may be a method for interference in active MS.

Animals↗
PubMed1996

Increased expression of interferon (IFN)-gamma together with IFN-gamma receptor in the rheumatoid synovial membrane compared with synovium of patients with osteoarthritis.

Data concerning the presence of T-cell-derived cytokines in the rheumatic joint are conflicting, challenging the hypothesis that rheumatoid arthritis (RA) is a T-cell-mediated disease. In this study synovial tissue specimens of 11 patients with RA and eight patients with osteoarthritis (OA) were stained for interferon-gamma (IFN-gamma) and its receptor. The level of expression of IFN-gamma was compared with that in tissue specimens of delayed-type hypersensitivity (DTH) reactions of the skin and of chronic tonsillitis. Furthermore, the percentage of T-lymphocytes which stained positive for IFN-gamma was determined using double staining techniques. IFN-gamma and its receptor were detected in all patients with RA and in 7/8 and 3/8, respectively, of patients with OA. Expression of IFN-gamma (P<0.02) and IFN-gamma receptor (P<0.01) in synovial tissue of patients with RA was more abundant compared with that in patients with OA. Although IFN-gamma could be detected in RA synovial tissue, the level of expression was less when compared with DTH reactions of the skin and tonsillitis. The percentage of CD3+ cells being positive for IFN-gamma was approximately 1% in RA, whereas in DTH reactions of the skin it was >90% and in tonsillitis approximately 30%. We conclude that the presence of IFN-gamma and its receptor in RA synovial tissue suggests a role for this cytokine in the ongoing immunological reaction of the inflamed joint.

Antigens, CD↗
PubMed1996

Functions of CD40 and its ligand, gp39 (CD40L).

Initially, a role for the interaction between CD40, expressed on B cells, and gp39 (CD40L), expressed on activated T cells, has been defined in humoral immunity. CD40-CD40L interaction is an essential signal for B cell proliferation, expression of activation markers, immunoglobulin production, and isotype switching. CD40-CD40L interaction is also required for formation of B memory cells and germinal centers, and signaling through CD40 prevents apoptosis of germinal center B cells. Defective expression of CD40L in humans leads to an inability to produce isotypes other than IgM (hyper IgM syndrome), and to an absence of germinal centers. More recent evidence indicates an expansion of the role of the CD40-CD40L axis in cellular interactions beyond antibody formation. Induced expression of CD40 on monocytes can lead to CD40L-activated monocyte effector mechanisms. In addition, CD40-CD40L interactions are crucially involved in development of autoimmune disease in a number of animal models. CD40-CD40L interactions also impact on growth regulation of certain carcinomas. Manipulation of CD40L has also been used to develop novel strategies for long-term antigen-specific tolerization of peripheral T cells. Finally, the CD40-CD40L axis is involved in thymic selection. Following is a comprehensive overview of CD40L-CD40 interactions in physiological and pathogenic cellular responses and a discussion of the therapeutic ramifications of these interactions.

Animals↗
PubMed1996

In vivo expression of interleukin-1 beta (IL-1 beta), IL-2, IL-4, IL-6, tumour necrosis factor-alpha and interferon-gamma in the fetal murine thymus.

Cytokines are known to play a role in T-cell lymphopoiesis as potent growth or differentiation factors, but many experiments focusing on their role in the thymus have been conducted only in vitro. We have thus used frozen sections obtained from fetal thymuses of normal C57BL 6 mice to investigate by immunohistochemistry the presence of interleukin-1 beta (I4-1 beta), IL-2. IL-4. IL-6. interferon-7 (IFN-7) and tumour necrosis facor-alpha (TNF-alpha). The results reveal that apart from IL-2, which was not detected, all these cytokines display a time-dependent expression pattern in the normal fetal thymus. First, production of IL-4, IL-6 and TNF-alpha is detected around days 13 14; this is followed by a second wave on days 16 17, with a production of IL-1 beta, IL-4 and IL-6, and finally, just before birth (day 19), by a third wave of IL-1 beta, IL-4, IL-6, IFN-7 and TNF-alpha production. This supports the hypothesis that cytokines play a rote in T-cell lymphopoiesis.

Animals↗
PubMed1995

An essential role for gp39, the ligand for CD40, in thymic selection.

The interactions between CD40 on B cells and its ligand gp39 on activated T helper cells are known to be essential for the development of thymus-dependent humoral immunity. However, CD40 is also functionally expressed on thymic epithelial cells and dendritic cells, suggesting that gp39-CD40 interactions may also play a role in thymic education, the process by which self-reactive cells are deleted from the T cell repertoire. Six systems of negative selection were studied for their reliance on gp39-CD40 interactions to mediate negative selection. In all cases, when the antigen/superantigen was endogenously expressed (in contrast to exogenously administered), negative selection was blocked by loss of gp39 function. Specifically, blockade of gp39-CD40 interactions prevented the deletion of thymocytes expressing V beta 3, V beta 11, and V beta 12, specificities normally deleted in BALB/c mice because of the endogenous expression of minor lymphocyte-stimulating determinants. Independent verification of a role of gp39 in negative selection was provided by studies in gp39-deficient mice where alterations in T cell receptor (TCR) V beta expression were also observed. Studies were also performed in the AND TCR transgenic (Tg) mice, which bear the V alpha 11, V beta 3 TCR and recognize both pigeon cytochrome c (PCC)/IEk and H-2As. Neonatal administration of anti-gp39 to AND TCR Tg mice that endogenously express H-2As or endogenously produce PCC prevented the deletion of TCR Tg T cells. In contrast, deletion mediated by high-dose PCC peptide antigen (administered exogenously) in AND TCR mice was unaltered by administration of anti-gp39. In addition, deletion by Staphylococcus enterotoxin B in conventional mice was also unaffected by anti-gp39 administration. gp39 expression was induced on thymocytes by mitogens or by antigen on TCR Tg thymocytes. Immunohistochemical analysis of B7-2 expression in the thymus indicated that, in the absence of gp39, B7-2 expression was substantially reduced. Taken together, these data suggest that gp39 may influence negative selection through the regulation of costimulatory molecule expression. Moreover, the data support the hypothesis that, for negative selection to some endogenously produced antigens, negative selection may be dependent on TCR engagement and costimulation.

Amino Acid Sequence↗
PubMed1995

Requirement of CTLA-4 counter receptors for IL-4 but not IL-10 elevations during a primary systemic in vivo immune response.

The CD28/CTLA-4 costimulatory signal is required for TCR-mediated T cell activation resulting in increased IL-2 production in vitro, but its role in IL-4 production is unclear and few studies have examined the function of CTLA-4/CD28 in the in vivo immune response. We have examined the in vivo effects of blocking the interaction of B7 with its ligands, CTLA-4 and CD28, in an IL-4 dominant in vivo immune response to goat anti-mouse IgD. This response is characterized by elevations in serum Igs preceded by elevations in IL-2 and the Th2 cytokines: IL-4, IL-9, and IL-10. The fusion protein CTLA4-Ig administered during the in vivo immune response to goat anti-mouse IgD caused an inhibition in elevations of IL-2, IL-4, and IL-9 gene expression at both day 3 and day 6 after immunization. In contrast, IL-10 cytokine gene expression as late as day 6 after immunization was not decreased. Cell sorting analysis demonstrated that TCR-alpha beta +, CD4+ T cells were the primary source of the elevated IL-10, suggesting that T cell activation leading to IL-10 gene expression may not require CTLA-4 ligand interactions. Similarly CTLA4-Ig completely blocked elevations in the number of IL-4- but not IL-10-secreting cells, as measured by ELISPOT, in both unsorted splenic cells and sorted CD4+, TCR-alpha beta+ T cells. In situ staining of spleen sections also showed inhibition of IL-4-producing cells. These results suggest that, with the notable exception of IL-10, interaction, of B7 with its ligands is required for elevated Th2 cytokine gene expression and secretion during a primary systemic IL-4-dominant response.

Abatacept↗
PubMed1995

Antigen detection in vivo after immunization with different presentation forms of rabies virus antigen: involvement of marginal metallophilic macrophages in the uptake of immune-stimulating complexes.

Several mechanisms have been postulated to explain the relatively high immunogenicity of antigens presented in immune-stimulating complexes (iscom). Their potency can in part be explained by the specific targeting of these structures to cells presenting antigens to the immune system. However, until now no method for the subcellular detection of iscom in situ was available. In the present study, a novel, fast and simple method for the detection of iscoms in situ is demonstrated. By making use of the lipophilic fluorescent carbocyanine dyes, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) and 3,3'-dioctadecyloxacarbocyanine perchlorate (DiO), rabies virus antigen and iscom prepared with this antigen were visualized with fluorescence microscopy. The labeled antigen and iscoms were observed in macrophages of spleen and liver of mice within 1-2 h after intravenous administration. When administered intramuscularly or in the footpad, uptake in macrophages of draining lymph nodes could be demonstrated. In the spleen, labeled inactivated virus antigen localized preferentially in the marginal zone macrophages and to a lesser extent in the red pulp macrophages. In contrast, antigen presented in iscom was taken up mainly by the marginal metallophilic macrophages and to a much lesser extend by marginal zone macrophages or follicular-dendritic and -B cells. This method enables the detection of iscom and membrane viruses and allows the analysis of their relation to antigen-presenting cells in situ. Here, we demonstrate that iscom containing rabies virus antigen are taken up by a subset of macrophages in the spleen distinct from those that take up inactivated rabies virus antigen not presented in iscom, thereby possibly explaining the observed difference in immunogenicity of these antigen preparations. Furthermore, we show a lower efficiency on the induction of humoral and cellular responses after intravenous immunization for both types of antigen when compared with subcutaneous immunization.

Animals↗
PubMed1995

Comparison of adjuvants for immune potentiating properties and side effects in mice.

Four types of adjuvants were evaluated as alternatives to the use of Freund's complete adjuvant in mice. The adjuvants evaluated included a water-in-oil emulsion (Specol), a microorganism (Lactobacillus), performed immune-stimulating complexes (ISCOM) containing rabies virus glycoprotein and a saponin, Quil A. The adjuvants and saline were combined with three weak immunogens (a synthetic peptide, a self antigen and a particulate antigen) and given by three different routes (intraperitoneal, subcutaneous and dorsal in the foot). The evaluation was based on clinical observations, behavioural studies, pathological lesions and capacity to support immunological responses to weak immunogens. Lesions were most severe after injection of antigen combined with Freund's adjuvant or Quil A, mild to moderate with Specol and minimal with Lactobacillus, iscom conjugates or saline. Despite pathological changes, no signs of prolonged pain or distress could be demonstrated based on clinical observations and behavioural studies. Minimal immunological responses were found after injection of antigen in combination with saline or Lactobacillus. T-cell activation and high antibody responses were found after injection of antigen-iscom conjugates or antigen in Freund's adjuvant emulsions. After Specol/antigen immunisations T-cell activation was demonstrated and high antibody titres were found except for Specol/self antigen immunisations. Presented data suggest that Specol is a possible alternative to Freund's complete adjuvant for the induction of an immune response against weak immunogens except possibly self antigens, for which performed iscoms seem very suitable.

Adjuvants, Immunologic↗
PubMed1995

In vivo cytokine profiles in allergic and irritant contact dermatitis.

Local cytokine profiles in skin biopsies from allergic and irritant patch test reactions were determined by in vivo immunohistochemistry to differentiate between these 2 clinically identical afflictions especially at the same time of final reading in diagnostic patch testing. Biopsies were taken from established allergic persons after specific allergic patch tests to epoxy resin (1%), and formaldehyde (1%) and from non-allergic individuals with irritant patch tests to sodium lauryl sulfate (10%) and formaldehyde (8%). At 72 h after application of the agents, significantly enhanced frequencies of dermal infiltrating cells, producing IL-alpha, IL-2, and IFN-gamma per 100 infiltrating cells in the dermis, were observed in allergic as well as irritant test patch reactions, as compared to normal skin. Significantly higher frequencies of IL-1alpha producing cells were observed in biopsies from epoxy resin (1%) allergen-affected and formaldehyde (8%) irritant affected skin. The allergic and irritant patch test reactions showed similar levels of expression of the Th1 cytokines IL-2 and IFN-gamma in the dermis, confirmed by probe based detection of IL-2 mRNA and IFN-gamma mRNA. In conclusion, the described similarity shows that allergens and irritants can induce the same profile of IL-1alpha, TNF-alpha, IL-2, and IFN-gamma production, resulting in the near impossibility of discriminating between allergic and irritant contact dermatitis at the time of patch test reading.

Allergens↗
PubMed1995

Migration of human antigen-presenting cells in a human skin graft onto nude mice model after contact sensitization.

Fluorescent contact chemical allergens provoke sensitization after application on both syngeneic and allogeneic skin grafts in mice. We attempted to determine whether the functional activity in a contact sensitization response of human skin graft was affected at the level of antigen uptake and migration. After xenogeneic skin transplantation, we examined the effect of topical exposure of the graft to rhodamine B isothiocyanate (RITC). This paper describes the migration of RITC-carrying cells and human major histocompatibility complex (MHC) class II DR (HLA-DR)+ cells, from the graft to mouse draining lymph nodes. As demonstrated by immunohistochemistry, grafting resulted in a time-dependent decrease of human HLA-DR+ and CD1a+ cells, and an increase of mouse MHC class II (Ia)+ cells within the graft. Application of RITC on a 3-week-old human skin graft showed optimal migration capability compared to 6- or 9-week-old grafts. In addition, the time-dependent increase of frequencies of RITC+ and HLA-DR+ cells in the draining lymph nodes, and the time-dependent decrease of HLA-DR+ cells in the 3-week-old human skin graft, were concurrent. Supporting these data, human cytokine interleukin-1 alpha (IL-1 alpha), IL-1 beta and tumour necrosis factor-alpha (TNF-alpha), analysis in situ revealed that cytokine production by keratinocytes, a property associated with dendritic cell migration, was preserved in the human skin graft. Thus, like dendritic cells in contact sensitization in allografted skin, dendritic cells from human xenografted skin onto nude mice are capable of migration to mouse draining lymph nodes after allergen application. Induction of contact hypersensitivity is possible in a human skin graft onto nude mice model, although the use of this ex vivo model to analyze contact sensitivity is probably limited to 3 weeks after transplantation.

Adult↗
PubMed1995

Activated rat T cells synthesize and express functional major histocompatibility class II antigens.

In the present report, we studied the presence and functional significance of major histocompatibility complex (MHC) class II antigen on rat T cells. Most rat T-cell lines cultured in vitro were found to be MHC class II+. Also, these T-cell lines were shown to synthesize MHC class II molecules. Immunohistochemical and flow cytometric double stainings for T-cell receptor (TCR) and MHC class II showed that in vivo as well a large proportion of T cells was MHC class II+. The immunohistochemical staining of spleen sections enabled us to characterize the MHC class II+ and MHC class II- T cells. It was shown that resting T cells in vivo were MHC class II-. In contrast, activated T cells, as determined by their localization in the marginal zone of the spleen, proved to be MHC class II+. Finally, T-cell clones were found to be able to present peptidic antigens, but could only poorly present more complex exogenous antigens, probably due to inefficient uptake of such antigens. These features would endow activated rat T cells with the capacity to present cell-specific self-proteins, such as TCR, to regulatory CD4+ MHC class II-restricted T cells, as was described by our group elsewhere.

Animals↗
PubMed1994

gp39-CD40 interactions are essential for germinal center formation and the development of B cell memory.

gp39, the ligand for CD40 expressed on activated CD4+ T helper cells, is required for the generation of antibody responses to T-dependent (TD) antigens. Treatment of mice with anti-gp39 in vivo inhibits both primary and secondary antibody formation to TD, but not T-independent antigens. However, the role of this receptor-ligand pair in the development of germinal centers and the generation of B cell memory is as yet undefined. Using an antibody to gp39, this study examines the in vivo requirement for gp39-CD40 interactions in the induction of germinal center formation, as well as in the generation of B cell memory. Animals were immunized, treated in vivo with anti-gp39, and evaluated using immunohistochemical staining for the presence of splenic germinal centers 9-11 d after immunization. The results demonstrate that the formation of germinal centers was completely inhibited as a result of treatment with anti-gp39. Moreover, adoptive transfer experiments demonstrate that the generation of antigen-specific memory B cells is also inhibited as a consequence of blocking gp39-CD40 interactions. Taken together, the data demonstrate that gp39-CD40 interactions are critical not only for the generation of antibody responses, but also in the development of B cell memory.

Animals↗
PubMed1994

In vivo T-B cell interactions and cytokine-production in the spleen.

T-B cell interactions have a central role in the development of humoral immunity. The binding of a 39 kDa protein (gp39), selectively expressed on activated Th cells, to its receptor CD40, on B cells, results in the initial B cell activation. Thereafter, Th cell derived cytokines regulate the differentiation of B cells into antibody-forming cells. Most of these data are derived from in vitro experiments. This article discusses in vivo experiments dealing with T-B interactions. First, the immunohistochemical analysis of T cell activation (gp39 expression), cytokine and antibody production in murine spleens after injection of model antigens (TNP-Ficoll, TNP-KLH, and rabbit anti-IgD antibodies). Second, the in vivo role of gp39 and cytokines in these immune responses. Finally, by combining these in vivo experiments with in vitro data we present an in vivo model for T cell dependent antibody responses.

Animals↗