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Biomedical subjects

K Blaser

Publications and source records attributed to K Blaser.

212 records · Page 12Linked to original sources
PubMedDate not supplied

IgE-mediated reactions to autoantigens in allergic diseases.

BACKGROUND: There is increasing evidence that IgE-mediated reactivity against autoantigens could play a role in the pathology of severe chronic atopic diseases. METHODS: Human mitochondrial managenese superoxide dismutase (MnSOD), acidic ribosomal P2 protein and cyclophilins were cloned by PCR, expressed as inclusion body proteins in Escherichia coli, purified by Ni2+-chelate affinity chromatography, refolded in vitro and used for further experiments. RESULTS: Human MnSOD, P2 ribosomal protein and cyclophilins respectively, show sequence identity and similarity of >50% and 70% to the corresponding allergens of Aspergillus fumigatus. The human proteins were able to bind IgE from sera of individuals sensitized to the mould proteins and to elicit strong skin reactions of the immediate type in these individuals. CONCLUSIONS: These observations provide evidence for autoreactivity to human proteins in allergic persons chronically sensitized to environmental allergens from A. fumigatus which share a high degree of sequence homology to the corresponding human proteins.

Allergens↗
PubMedDate not supplied

Tapping allergen repertoires by advanced cloning technologies.

BACKGROUND: Complex allergenic sources such as moulds, foods and mites contain complex panels of IgE-binding molecules which need to be cloned, produced and characterized in order to mimic the entire allergenicity of whole extracts reconstituted by mixing single standardized recombinant allergens. METHODS: Phage surface display of cDNA libraries selectively enriched for allergen-expressing clones using IgE from allergic patients allows rapid isolation of large panels of allergens. For the characterization of all different clones present in enriched cDNA libraries in a fast and cost-effective way, high-throughput screening technology is required. RESULTS: The combination of selective enrichment of cDNA libraries based on biopanning against serum IgE from sensitized patients and automated robot technology for picking and high-density gridding of clones onto filter membranes, followed by hybridization, enables fast identification of all the different clones present in an enriched library. The consequent application of selective enrichment and robotic-based screening allows, within weeks, cloning and characterization of the whole allergenic repertoire of any organisms. CONCLUSIONS: Robotic-based high-throughput screening of clones selected for IgE-binding capacity from phage surface-displayed cDNA libraries of Aspergillus fumigatus, Cladosporium herbarum, Coprinus comatus, Malassezia furfur, peanut and human lung tissue allowed rapid characterization of 81, 28, 37, 27, 8 and 151 different sequences, respectively. All these cDNAs bear a high probability to encode allergens derived from the respective allergenic source.

Allergens↗
PubMedDate not supplied

Mechanism of IL-10-induced T cell inactivation in allergic inflammation and normal response to allergens.

BACKGROUND: Induction of specific unresponsiveness (tolerance/anergy) in peripheral T cells and recovery by cytokines from the tissue microenvironment represent two key steps in specific immunotherapy (SIT) with whole allergen or antigenic T cell peptides. METHODS: Antigen-specific T cell responses and molecular mechanisms of T cell inactivation were investigated during conventional SIT, T cell epitope peptide immunotherapy and natural exposure to bee venom in allergic and hyperimmune individuals. RESULTS: T cell unresponsiveness, initiated by autocrine action of IL-10, is characterized by suppressed proliferative and cytokine responses. The unresponsive T cells can be reactivated by different cytokines that may mimic the microenvironmental cytokine influence. IL-10 initiates peripheral tolerance by blocking the CD28 costimulatory signal in T cells. Coprecipitation experiments reveal that upon stimulation CD28 and IL-10 receptor are physically associated in T cells. Accordingly, IL-10 binding to its receptor inhibits CD28 tyrosine phosphorylation, the initial step of the CD28 signaling pathway. This leads to inhibition of phosphatidylinositol 3-kinase p85 binding to CD28. IL-10 only affects T cells that receive a stimulation with low numbers of triggered T cell receptors and that require costimulatory signals by CD28. CONCLUSION: These data demonstrate the pivotal role of autocrine IL-10 and the interaction of its receptor with CD28 in the induction of T cell tolerance as an immunoregulatory mechanism controlling antigen-specific T cell responses.

Allergens↗
PubMedDate not supplied

Histamine upregulates Th1 and downregulates Th2 responses due to different patterns of surface histamine 1 and 2 receptor expression.

Histamine, which acts via G protein-coupled receptors, is an important mediator of immediate hypersensitivity and is also able to influence the nature of T cell responses. We demonstrated that TH1 and Th2 cells express distinct surface histamine receptor patterns and that Th1-type responses are enhanced by histamine, whereas Th2-type responses are negatively regulated, due to different intracellular signals generated by histamine stimulation. These findings account for negative feedback regulation in a wide variety of pathologies.

Cells, Cultured↗
PubMedDate not supplied

Clinical and immunological features of patients with interleukin-5-producing T cell clones and eosinophilia.

Recent work suggests that in some patients with the hypereosinophilic syndrome, a clone of abnormal T cells produces large amounts of interleukin-5. In this study, we examined 60 patients with idiopathic eosinophilia. Sixteen patients had circulating T cells with an aberrant immunophenotype that, in most cases, were associated with different forms of skin inflammation. The abnormal T cells produced large amounts of interleukin-5, which may have increased eosinophil differentiation in the bone marrow of these patients.

Clone Cells↗
PubMedDate not supplied

Human peripheral blood eosinophils express and release interleukin-8.

Eosinophils can synthesize various cytokines. We demonstrate that interleukin-8 (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 (PAF). Priming with granulocyte/macrophage-colory-stimulating factor and a subsequent 25-min stimulation with RANTES or PAF resulted in release of IL-8 from highly purified human eosinophils in vitro.

Asthma↗
PubMedDate not supplied

Allergen specificity and endothelial transmigration of T cells in allergic contact dermatitis and atopic dermatitis are associated with the cutaneous lymphocyte antigen.

Recent investigations have indicated a role for antigen-specific T lymphocytes in the local skin immunity. The cutaneous lymphocyte antigen (CLA) is supposed to represent a skin-homing receptor for T cells. Inhibition experiments with specific monoclonal antibody demonstrate that CLA participates in selective transendothelial migration of memory/effector T cells in vitro by interaction with E-selectin on endothelial cell layers after activation with proinflammatory cytokines. In addition, the receptor-ligand pairs VLA-4/VCAM-1 and LFA-1/ICAM-1 are involved in this process. Moreover, only CLA+, CD45RO+ (memory/effector) T cells freshly isolated from peripheral blood of patients with allergic contact dermatitis or atopic dermatitis specifically proliferate in response to the respective allergen. CLA-, CD45RO- T cells from these patients do not respond to the allergens. In contrast, memory T cells from asthmatic individuals and patients with both asthma and atopic dermatitis express the allergen specificity in both T cell subsets. Tetanus toxoid, a systemically acting antigen, also induces a proliferative response in both CLA+ and CLA- memory/effector T cell subsets. These results strongly support the selective role of CLA in homing T cells to the cutaneous tissues and therefore playing a role in the local immunity and inflammatory reactions of the skin.

Adult↗
PubMedDate not supplied

Cloning, production, characterization and IgE cross-reactivity of different manganese superoxide dismutases in individuals sensitized to Aspergillus fumigatus.

BACKGROUND: Manganese superoxide dismutase (MnSOD) from Aspergillus fumigatus has been demonstrated to be an allergen showing a high degree of homology with phylogenetically distant MnSODs. We describe cloning, production and characterization of MnSODs from different species. METHODS: MnSODs were cloned by PCR, expressed as inclusion body protein in Escherichia coli, purified by Ni2+-chelate affinity chromatography and characterized. RESULTS: The MnSODs from A. fumigatus, man, yeast, Drosophila melanogaster and E. coli show about 50% identity and 70% similarity on the primary structure. All proteins were produced at a high level in E. coli and refolded to achieve enzymatic activity. The proteins were able to bind IgE from sera of individuals sensitized to the A. fumigatus MnSOD. CONCLUSIONS: MnSOD represents a novel pan-allergen restricted to individuals sensitized to A. fumigatus.

Allergens↗
PubMedDate not supplied

Cholesterol and phospholipid content of 3T3 cells and transformed derivatives.

For 3T3, PY-3T3 and SV40-3T3 cells, the contents of total lipid, cholesterol and phospholipid were determined. Weight of total lipid per cell correlates closely with cellular volume as determined microscopically. This correlation is not observed for cholesterol of phospholipid content per cell. Cholesterol content per cm2 cellular surface area is found about fifty percent higher in the transformed cell lines compared to 3T3 cells. This result is discussed in relation to thermal transitions observed in physical properties of the plasma membrane of these cells as well as in lamellar phospholipid/water model systems containing cholesterol.

Cell Line↗
PubMedDate not supplied

Correlation between blood eosinophils, T-helper cell activity markers and pulmonary function in patients with allergic and intrinsic asthma.

We studied 21 asthmatic patients (17 with allergic asthma and 4 with intrinsic asthma) who on the date of admittance to our clinic presented eosinophil values higher than 400 eosinophils/mm3 and a marked alteration in pulmonary function. From the day of admittance, eosinophils/mm3 were followed-up for 28-30 days, along with T-helper cell activity markers (IL-2R+) and pulmonary function markers. In patients with allergic asthma with or without topical corticoid treatment, and in patients with intrinsic asthma under treatment with topical corticoids, we observed that the number of eosinophils/mm3 and the number of activity markers (IL-2R+) decreased progressively, with subsequent clinical recovery and improvement in pulmonary function. This was not observed in patients with intrinsic asthma not treated with topical corticoids. We conclude that, as previously demonstrated, the activation and proliferation of eosinophils bear a close relationship with the previous activation of T-helper cells (CD4).

Administration, Topical↗
PubMedDate not supplied

P-glycoprotein expression in circulating blood leukocytes of patients with steroid-resistant asthma.

P-Glycoprotein is a transmembrane efflux pump for different lipophilic drugs including glucocorticosteroids. Thus, upregulation of P-glycoprotein may provide a mechanism for reduced glucocorticosteroid responses as they occur in steroid-resistant asthma. To address this issue, we have examined freshly isolated peripheral blood mononuclear cells and granulocytes with regards to P-glycoprotein functional and surface expression. Using two-color immuno fluorescence techniques, we demonstrated a direct correlation between the efflux of the fluorescent dye Rh 123 and P-glycoprotein surface expression in lymphocytes, NK (natural killer) cells, monocytes and granulocytes. P-Glycoprotein levels varied widely between different leucocytes, with NK cells and CD8+ T cells having high, and granulocytes having no detectable levels. There was no evidence for upregulation of P-glycoprotein expression in any cell type from patients with steroid-resistant asthma compared to patients with steroid-sensitive or mild asthma. These results suggest that increased P-glycoprotein expression can be excluded as a mechanism for steroid resistance. Interestingly, a down regulation of P-glycoprotein expression in B cells was associated with systemic glucocorticosteroid treatment in vivo and in vitro. Whether this phenomenon may account for reduced immunoglobulin levels associated with oral glucocortico-steroid therapy remains to be determined.

ATP Binding Cassette Transporter, Subfamily B, Mem↗