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Biomedical subjects

K Blaser

Publications and source records attributed to K Blaser.

At least 109 records · Page 6Linked to original sources
PubMed1996

A case of hypereosinophilic syndrome is associated with the expansion of a CD3-CD4+ T-cell population able to secrete large amounts of interleukin-5.

Interleukin-5 (IL-5) is the major soluble factor able to mediate hypereosinophilia. We report a case of hypereosinophilic syndrome in which the presence of a population of CD3-CD4+ cells able to overproduce IL-5 was shown. The lack of CD3 and TCRAB membrane expression on otherwise phenotypically normal mature T lymphocytes together with the absence of detectable TCRBV mRNA and clonal rearrangement of TCRB gene suggested that the abnormal lymphocyte population was the expression of a peripheral T-cell lymphoma with an indolent clinical course. Peripheral blood lymphocytes enriched in this population were able to secrete high levels of IL-5 but not IL-4, and no IL-2 or interferon-gamma, when stimulated in vitro with phytohemagglutinin and phorbol myristate acetate. The serum contained eosinophil survival factors whose activity was partially neutralized by a specific antihuman IL-5 antibody. This observation further emphasized the relationship between hypereosinophilic syndrome. IL-5, and T-cell lymphoproliferative disorders.

Aged↗
PubMed1996

Expression and function of the Fas receptor on human blood and tissue eosinophils.

The interaction between activated T cells and eosinophils has been proposed to play an important role in the pathogenesis of allergic diseases. T cell-derived cytokines such as interleukin-5 and granulocyte/macrophage colony-stimulating factor inhibit eosinophil apoptosis and may therefore contribute to the development of tissue and blood eosinophilia in these disorders. Withdrawal of these cytokines leads to eosinophil apoptosis in vitro. In contrast, the mechanisms which actively induce apoptosis in eosinophils are at present not completely understood. In this study, we demonstrate that freshly isolated human eosinophils express mRNA and protein for the Fas receptor. Using anti-Fas monoclonal antibody (mAb), we show that Fas activation accelerates apoptotic eosinophil death in vitro. Moreover, treatment of nasal polyps ex vivo with anti-Fas mAb decreased eosinophilic tissue inflammation. However, we observed that blood as well as tissue eosinophils derived from some eosinophilic donors do not express functional Fas receptors, although Fas protein is normally expressed in these cells. This implies that the susceptibility of the Fas receptor is a matter of regulation in eosinophils as previously observed in other systems. These data suggest that Fas ligand/Fas interactions are involved in the regulation of eosinophil apoptosis and that defects in this system could contribute to the accumulation of these cells in allergic and asthmatic diseases.

Antibodies, Monoclonal↗
PubMed1996

A strict requirement of interleukin-4 for interleukin-4 induction in antigen-stimulated human memory T cells.

The role of interleukin-4 (IL-4) in the induction of IL-4 in mouse T cells is well established, but conflicting results have been reported with anti-CD3-primed human T cells and T cell clones. Therefore, IL-4 regulation was investigated in short-term cultured human T cells primed in vitro with either a superantigen or a hapten, nickel sulfate (NiSO4), for 3 days and expanded with IL-2 for another 5 days. Under these conditions, antigen-specific IL-4 producing T cells were generated in 35/40 cultures. Priming for IL-4 production was abrogated in all cultures by anti-IL-4 antibody or soluble IL-4 receptor (sIL-4R). Primed T cells that were IL-4- when cultured with IL-2 only developed an IL-4 producing phenotype when primed and expanded in the presence of exogenous IL-4. T cells primed in the presence of either endogenous or exogenous IL-4 produced 10-200-fold more IL-4 than T cells primed in the presence of anti-IL-4 antibody or sIL-4R. While IL-4 induction was absolutely dependent on IL-4, neither endogenous nor exogenous IL-4 influenced IFN-gamma synthesis. Most importantly, IL-4 induced and sIL-4R abolished priming for IL-4 production even in NiSO4-specific memory T cells from sensitized individuals. Thus, IL-4 induction in antigen-specific human memory T cell populations absolutely required IL-4. The IL-4 pathway of memory T cells retained a remarkable plasticity in sensitized individuals.

Adult↗
PubMed1996

The interleukin-8 receptor B and CXC chemokines can mediate transendothelial migration of human skin homing T cells.

We studied the involvement of chemokines that bind to G protein-coupled receptors in the migration of skin homing T cells across a bilayer vascular construct (BVC) consisting of a fibroblast matrix underneath an activated endothelial (EC) monolayer. Based on the expression of the cutaneous lymphocyte-associated antigen (CLA), a skin homing receptor, CD45R0+ T cells freshly isolated from blood or HUT-78 cutaneous T lymphoma cells were separated into CLA+ and CLA- subpopulations. These T cells were incubated on interleukin (IL)-1 beta and tumor necrosis factor-alpha-activated EC, and the number of transmigrated cells was determined. The chemokine IL-8 was selectively involved in the enhanced migration of CLA+ T cells across activated EC as demonstrated by blocking antibody to IL-8 but not to GRO-alpha, MCP-1 and RANTES. Identical results were obtained with both human umbilical vein EC (HUVEC) and microvascular skin EC (HDMEC). Pertussis toxin selectively inhibited the enhanced transendothelial migration (TEM) of CLA+ T cells, suggesting that CLA-dependent TEM depends on Gi protein-transmitted signals. Moreover, the IL-8 receptor B (IL-8RB) appeared to be functionally involved in TEM, as demonstrated by receptor desensitization with the CXC chemokines IL-8 and GRO-alpha and by blocking the IL-8RB with specific monoclonal antibodies. Although only the IL-8RB was involved in CLA-dependent TEM, mRNA encoding IL-8RA and IL-8RB was expressed by both CLA+ and CLA- T cells. This correlated with IL-8RA and IL-8RB surface expression on these cells. Thus, the IL-8RB is selectively functional in TEM of T cells expressing the skin homing receptor CLA. Our results demonstrate a critical role for IL-8 and possibly other IL-8RB ligands in addition to the IL-8RB in TEM and suggest the involvement of these molecules in the homing of specific T cells to inflamed skin.

Animals↗
PubMed1996

Automated serology with recombinant allergens. A feasibility study.

Diagnosis of allergic conditions is based on skin prick- and/or intradermal tests and on serology. Both methods make use of allergenic preparations and the results mainly depend on the quality of the substances applied and on the reactivity of the subjects. Recombinant allergens can be produced as highly pure proteins. They may contribute to a significant improvement of the diagnosis of allergic diseases provided that the allergens became available in a pure, fully antigenic form suitable for routine assessments. We have studied the diagnostic properties of recombinant Aspergillus fumigatus allergen I (rAsp f I/a), a major allergen recognised by about 60% of the A. fumigatus allergic individuals, to test the feasibility of using recombinant allergens for automated serology in the Pharmacia CAP System, a new solid-phase immunoassay. ImmunoCAPs carrying immobilised rAsp f I/a were produced and evaluated using sera from well characterised patients with allergic bronchopulmonary aspergillosis (ABPA), allergic asthmatics with or without A. fumigatus sensitisation, and healthy control persons. The clinical parameters used for the diagnosis of allergy to A. fumigatus were RAST and skin test reactivity to commercial A. fumigatus extracts. IgE antibodies recognising rAsp f I/a were determined by a direct antigen-specific ELISA and with the newly developed rAsp f I/a ImmunoCAPs. Quantitative results from the two rAsp f I/a detection systems correlated closely, indicating that this recombinant allergen can be incorporated in the Pharmacia CAP System with unaltered antigenic activity. The behaviour of a panel of recombinant A. fumigatus allergens in the Pharmacia CAP System will be evaluated in the near future to assess the potential of recombinant allergens for the automated diagnosis of allergic conditions.

Allergens↗
PubMed1996

Allergen dose dependent cytokine production regulates specific IgE and IgG antibody production.

The elicitation of a specific immune response against allergens depends on the recognition of antigenic determinants (epitopes) by specific T and B lymphocytes. In order to determine the relevant epitopes for human T and B cells and their features in the regulation and production of specific IgE and/or IgG antibodies, we have investigated the immune response to bee venom phospholipase A2 (PLA) in allergic and non-allergic subjects. This enzyme represents the major allergen in bee sting allergy. It consists of 134 amino acid residues with a carbohydrate side chain at position 13 and is available as recombinant protein. We have developed PLA-specific T-cell clones from bee sting allergic and non-allergic human subjects. Using a panel of dodecapeptides overlapping in 10 residues and a large set of 18-25 mer overlapping peptides, we detected three epitopes that were recognized by peripheral blood T-cells and T-cell clones. A fourth determinant involved the carbohydrate moiety on Asn13 of PLA. Whereas the CHO-depending epitope seems to be mostly active in allergics, the other three epitopes are equally recognized by peripheral blood mononuclear cells (PBMC) of both allergic and non-allergic individuals. In T-cell clones, the ratio of IL-4/IFN gamma cytokines and the quality of the activating signal depend on the strength of the binding of the MHC-II/Ag/TcR complex between APC and T-cells. The number of antigen-specific APC-T-cell contact sites can be varied in vitro by changing the dose of antigen added to the cell culture. While isotype switch for both IgE and IgG4 requires IL-4, this cytokine suppresses antigen-specific IgG4 production by already switched B-cells. Therefore, IL-4 and IFN gamma display counter-regulatory effects on the production of IgE being responsible for atopic states and IgG4 antibodies which are signs of a normal immune response to allergen and act as protective antibodies. The combination of this counter-regulation of IgE and IgG4 antibodies with the fundamental law of mass action for chemical equilibrium reactions revealed that the antigen concentration governs to a great part the ratio of IL-4/IFN gamma secretion and therefore the formation of IgE and IgG and allergy or protection, together with the equilibrium constant K, which represents immunological individuality and a measure of Ag presentation.

Allergens↗
PubMed1996

Cloning Aspergillus fumigatus allergens by the pJuFo filamentous phage display system.

A cDNA library from Aspergillus fumigatus has been displayed on the surface of filamentous phage M13 and screened for gene products binding to human serum IgE. The physical linkage of cDNA gene products to the genetic information required for their production, achieved by exploiting the high-affinity interaction of the Jun and Fos leucine zippers, allows rapid and easier screening of large libraries in semifluid systems. The pJuFo cloning vector is designed to display proteins on the surface of phage and allows selective isolation of genes by gene product-ligand interaction. Thus the system is applicable to clone cDNA that encodes proteins for which a ligand is available. Herein we show that phage expressing IgE binding proteins from A. fumigatus can be enriched and separated from nonspecific phage by using serum IgE from A. fumigatus-allergic individuals coated to plastic dishes. Subsequently, the proteins can be produced in high amounts in Escherichia coli and purified for usage in allergy testing.

Allergens↗
PubMed1996

Skin test reactivity to recombinant Aspergillus fumigatus allergen I/a in patients with cystic fibrosis.

We evaluated the diagnostic value of recombinant Aspergillus fumigatus allergen I/a (rAsp f I/a) for skin testing in cystic fibrosis (CF) patients with allergic bronchopulmonary aspergillosis (ABPA), allergy to A. fumigatus and in CF controls not allergic to A. fumigatus. Skin prick test reactions to rAsp f I/a were 8.5-fold stronger in A.-fumigatus-allergic and 3.3-fold stronger in ABPA patients compared to the CF controls. Three out of 6 well-characterized ABPA patients had positive skin prick test reactions to rAsp f I/a; the same number reacted to crude A. fumigatus extracts. The skin prick test results to rAsp f I/a were significantly correlated with those to crude and commercial preparations. According to these results, rAsp f I/a represents a defined allergen that provides the possibility to perform skin prick tests in CF patients in a highly standardized way. In future, a larger panel of recombinant allergens might also pick up those CF patients with ABPA and allergy to A. fumigatus who did not react to this single allergen.

Adolescent↗
PubMed1996

Automated specific IgE assay with recombinant allergens: evaluation of the recombinant Aspergillus fumigatus allergen I in the Pharmacia Cap System.

BACKGROUND: We report the results of a study comparing the recombinant Aspergillus fumigatus allergen 1 (rAsp f I) to commercial A. fumigatus extracts in serological assays. Pharmacia CAP System and skin tests. OBJECTIVE: The study was designed to test the feasibility of using recombinant allergens in an automated serology system for determination of allergen-specific IgE. METHODS: Patients with allergic bronchopulmonary aspergillosis (ABPA), asthmatics with A. fumigatus allergy and control subjects, who included allergic asthmatics without allergy to A. fumigatus and healthy subjects, were investigated. All subjects were characterized with respect to their total IgE level, radio allergosorbent test to A. fumigatus and skin test reactivity to both commercial A. fumigatus extracts and recombinant rAsp f I protein. RESULTS: All patients with ABPA (n = 30) showed positive skin test reactions with commercial A. fumigatus extracts, and 24 were sensitized to rAsp f I by the same criterion. The 10 patients with asthma and A. fumigatus allergy showed positive skin reactions to at least one commercial extract, and five reacted to rAsp f I. All control subjects (n = 19) scored negatively in skin tests to A. fumigatus extracts and rAsp f I and showed no detectable rAsp f I-specific IgE. ImmunoCAP carrying immobilized rAsp f I were evaluated using sera from all individuals described and the results compared with those obtained with the rAsp f I-specific ELISA for IgE. The data obtained with the two rAsp f I-specific detection systems correlated closely (r = 0.997) and were in perfect agreement with the skin test results. CONCLUSION: The data show that rAsp f I can be used as immobilized allergen in the Pharmacia CAP System indicating the feasibility of using recombinant allergens for an automated serological diagnosis of allergic diseases. However, every recombinant allergen needs to be evaluated individually for its performance if applied to a new diagnostic technology.

Adult↗
PubMed1996

Lack of T-cell-mediated recognition of the fusion region of the pml/RAR-alpha hybrid protein by lymphocytes of acute promyelocytic leukemia patients.

In previous studies, it was shown that the fusion region of the pml/RAR-alpha protein, expressed by acute promyelocytic leukemia (APL) cells, can be specifically recognized in vitro by donor (D. E. ) CD4 T cells in a HLA class II DR11-restricted fashion. We present here the results on the recognition of several pml/RAR-alpha peptides by APL patients expressing HLA DR11. The in vitro immunization of peripheral blood lymphocytes from four patients in remission (S. R., F. R., M. M., P. G.) with BCR1/25, a 25-mer pml/RAR-alpha, did not elicit either a polyclonal or a clonal immune response specific to the peptide. We then generated new donor anti-pml/RAR-alpha CD4(+) T-cell clones. These clones were tested for their recognition of BCR1/25. One clone (C3/5, CD3(+), CD4(+), CD8(-)) was selected for further analysis. Clone C3/5 showed specific proliferation, cytotoxicity, and cytokine (tumor necrosis factor alpha, granulocyte-macrophage colony-stimulating factor) production when challenged with autologous lymphoblastic cell lines pulsed with peptide BCR1/25. C3/5 cells developed specific proliferation and cytotoxicity when challenged with peptide-pulsed lymphoblastic cell lines and peripheral blood lymphocytes from the four DR11(+) APL patients. APL blasts, available only from patients F. R. and P. G., were not lysed by C3/5 and were unable to present peptide BCR1/25. Incubation of APL cells with IFN-gamma failed to induce HLA class II molecules and recognition by the C3/5 clone. Since APL cells do not express HLA class II molecules, we tested in two donors (D. E. and C. H. R.) and in patients S. R. and P. G. whether the use of 9-mer peptides (BCR1/9) would generate a CD8/HLA class I-restricted response. No peptide-specific T-cell line or clone could be generated from both donors and patients. These findings are discussed in relation to possible therapeutic approaches to the immunotherapy of APL.

Binding Sites↗
PubMed1995

IL-8 is expressed by human peripheral blood eosinophils. Evidence for increased secretion in asthma.

Eosinophils possess the capacity to synthesize various cytokines. We demonstrate that IL-8 mRNA and protein are constitutively expressed by freshly isolated resting human eosinophils. Most of the patients with bronchial asthma or atopic dermatitis show evidence for up-regulated IL-8 protein expression in eosinophils but not in neutrophils, suggesting that an eosinophil-specific cytokine may act in these patients. To investigate whether the intracellular IL-8 can be released, eosinophils were stimulated by different cytokines and platelet-activating factor. Priming with granulocyte-macrophage CSF and a subsequent 25-min stimulation with RANTES or platelet-activating factor resulted in release of IL-8 from highly purified human eosinophils in vitro. As the eosinophil is the predominant cell in asthmatic inflammation, we determined IL-8 concentrations in bronchoalveolar lavage fluids from normal individuals and asthmatic patients. Bronchoalveolar lavage fluids from patients with bronchial asthma consistently demonstrated high IL-8 concentration compared with the controls. This suggests that IL-8 is released in vivo by inflammatory bronchial cells in asthma.

Asthma↗
PubMed1995

Circulating allergen-reactive T cells from patients with atopic dermatitis and allergic contact dermatitis express the skin-selective homing receptor, the cutaneous lymphocyte-associated antigen.

The cutaneous lymphocyte-associated antigen (CLA) is the major T cell ligand for the vascular adhesion molecule E-selectin, and it has been proposed to be involved in the selective targeting of memory T cells reactive with skin-associated Ag to cutaneous inflammatory sites. To further investigate the relation of CLA and cutaneous T cell responses, we analyzed the CLA phenotype of circulating memory T cells in patients with allergic contact dermatitis and atopic dermatitis (AD) alone vs in patients manifesting bronchopulmonary atopy (asthma with or without AD) and nonallergic individuals. Significant T cell proliferative responses to Ni, a contact allergen, and to the house dust mite (HDM), an allergen to which sensitization is often observed in AD and/or asthma, was noted only in allergic and atopic individuals, respectively. When the minor circulating CLA+CD3+CD45RO+ subset was separated from the major CLA-CD3+CD45RO+ subpopulation in Ni-sensitive subjects, the Ni-dependent memory T cell response was largely confined to the CLA+ subset. A similar restriction of the T cell proliferative response to the CLA+ memory subset was observed for HDM in patients with AD alone. In HDM-sensitive patients with asthma with or without AD, however, the CLA- subset exhibited a strong antigen-dependent proliferation, in contrast to patients with AD alone, whose CLA- subset proliferated very weakly to HDM. In asthma with or without AD, the HDM-dependent proliferation slightly predominated in the CLA- when compared to the CLA+ subset. The functional linkage between CLA expression and disease-associated T cell effector function in AD was also demonstrated by the finding that the circulating CLA+ T cell subset in AD patients, but not nonatopic controls, selectively showed both evidence of prior activation (human histocompatibility antigen-DR expression) and spontaneous production of interleukin 4 but not interferon-gamma. Taken together, these observations demonstrate the correlation of CLA expression on circulating memory T cells and disease-associated memory T cell responses in cutaneous hypersensitivity, and they suggest the existence of mechanisms capable of sorting particular T cell Ag specificities and lymphokine patterns into homing receptor-defined memory subsets.

Adult↗
PubMed1995

Migration of skin-homing T cells across cytokine-activated human endothelial cell layers involves interaction of the cutaneous lymphocyte-associated antigen (CLA), the very late antigen-4 (VLA-4), and the lymphocyte function-associated antigen-1 (LFA-1).

The cutaneous lymphocyte-associated Ag (CLA) is expressed by a subset of circulating memory/effector T cells and by the vast majority of skin-infiltrating T cells. CLA is thought to target skin-associated T cells to inflammatory skin sites by interacting with endothelial cell ligand E-selectin (CD62E). We have examined adhesion molecules involved in the migration of human CLA+ and CLA- memory/effector T lymphocytes through IL-1- and TNF-alpha-activated and nonactivated HUVEC layers under static (nonflow) conditions. CLA-enriched memory/effector T lymphocytes migrated more actively across cytokine-activated HUVEC than CLA-depleted memory/effector T cells. This enhanced migration is dependent on the CLA/E-selectin interaction. mAb to very late Ag-4 (VLA-4) and vascular cell adhesion molecule-1 (VCAM-1) blocked the migration of CLA-enriched, but not of CLA-depleted, T cells across activated HUVEC. The observation that anti-VLA-4 and anti-CLA mAb did not show additional inhibition supports the concept that CLA and VLA-4 are sequentially involved in the extravasation. The fact that only CLA+ T cells were inhibited by the anti-VLA-4 mAb suggests that, in this system, CLA engagement is required for using the VLA-4/VCAM-1 pathway. Our studies demonstrate that CLA+ T cells use LFA-1/intercellular leukocyte adhesion molecule-1 (ICAM-1) for transmigration but that CLA expression is not required for the LFA-1/ICAM-1-dependent transmigration because anti-CD18/CD11a mAbs and anti-ICAM-1 mAbs were able to block T cell migration regardless of the activation state of HUVEC or the CLA expression by T cells. Taken together, our results suggest that CLA has a homing function in conducting the T cell to interact with LFA-1/ICAM-1 and/or VLA-4/VCAM-1; this results in enhanced adhesion and migration across cytokine-activated endothelial cells.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1995

Carbohydrate-dependent, HLA class II-restricted, human T cell response to the bee venom allergen phospholipase A2 in allergic patients.

The T cell-independent antibody response to polysaccharide antigen (Ag) is believed to result from their inability to bind major histocompatibility complex (MHC) restriction elements. However, recent studies using glycosylated analogues of known immunogenic peptides revealed that glycopeptides can interact with MHC molecules and are able to elicit specific T cell responses in experimental animals. This raises questions about the possible role which carbohydrates can play in T cell responses following natural exposure to glycoprotein antigens. Analyzing the fine specificity of the human T cell response against the major bee venom allergen phospholipase A2 (PLA), a 16-20-kDa protein glycosylated at a single site (Asn13), we have identified several T cell clones which proliferate in response to the glycoprotein but not to its non-glycosylated variants. Neither the carbohydrate moiety alone nor the combination of carbohydrate and non-glycosylated protein could substitute for the intact glycoprotein. Antibody directed against the carbohydrate moiety inhibited Ag-induced proliferation of these clones whereas control clones with known peptide specificity were not affected, providing additional evidence for the involvement of carbohydrates in T cell recognition. Moreover, peripheral blood mononuclear cells of two individuals from whom glycosylation-dependent T cell clones have been isolated showed significantly higher proliferation in response to glycosylated compared to non-glycosylated Ag, suggesting that glycosylation can contribute in some cases extensively to the immunogenicity of a glycoprotein Ag. Thus, this report shows that glycosylation-dependent Ag recognition by T cells can also occur following natural exposure to a glycoprotein.

Allergens↗