15. Mainzer Allergie-Workshop 2003

Production of interleukin-13 by human dendritic cells after stimulation with protein allergens is a key factor for induction of T helper 2 cytokines and is associated with activation of signal transducer and activator of transcription-6

Dendritic cells (DC) are able to induce not only T helper 1 (Th1) but also Th2 immune responses after stimulation with allergens. While DC-derived interleukin (IL)-12 and IL-18 are the key factors for the induction of Th1 cells, early signals being involved in Th2 differentiation are less well characterized so far. To analyse such early signals we used an antigen-specific setting with CD4+ T cells from atopic donors stimulated in the presence of autologous mature DC, which were pulsed with different allergen doses. The addition of increasing amounts of allergen during DC maturation with tumour necrosis factor-alpha, IL-1beta and prostaglandin E2 resulted in enhanced secretion of IL-6 and IL…

Direct evidence that FK506 inhibition of FcεRI-mediated exocytosis from RBL mast cells involves calcineurin

eRI-mediated exocytosis of preformed mediators from mast cells and basophils (e.g. histamine, serotonin, beta-hexosaminidase) is sensitive to the immunosuppressants cyclosporin A and FK506 (IC 50 200 and 4 n M , respectively) but not rapamycin. The mechanism of inhibition does not appear to involve tyrosine phosphorylation, hydrolysis of inositol phosphates or calcium flux. Here we report experiments using a molecular approach to assess the role of calcineurin, a serine/threonine phosphatase thought to be the primary pharmacological target of these drugs. Calcineurin’s activity requires association of its catalytic (A) subunit with an intrinsic regulatory (B) subunit. We hypothesized that c…

Coupling of Contact Sensitizers to Thiol Groups is a Key Event for the Activation of Monocytes and Monocyte-Derived Dendritic Cells

Strong contact sensitizers are able to induce distinct signal transduction mechanisms in antigen-presenting cells by coupling to cell proteins. The predominant target structures of haptens are thought to be thiol and amino groups in cysteine and lysine residues. We studied whether coupling of small reactive chemicals to thiol or amino groups might be responsible for the activation of monocytes and mature monocyte-derived dendritic cells. Human peripheral blood mononuclear cells were stimulated in vitro with subtoxic concentrations of the strong haptens 5-chloro-2-methylisothiazolinone plus 2-methylisothiazolinone and 2, 4, 6-trinitrochlorobenzene, the thiol-reactive reagents N-hydroxymaleim…

Activation and translocation of p38 mitogen-activated protein kinase after stimulation of monocytes with contact sensitizers.

Recently we described the induction of tyrosine phosphorylation by contact sensitizers as an early molecular event during the activation of antigen- presenting cells. In this study, the role of the p38 mitogen-activated protein kinase for the activation of human monocytes after exposure to four structurally unrelated contact sensitizers was analyzed in comparison with the irritant benzalkonium chloride and an inductor of oxidative stress (H 2 O 2 ) using immunofluorescence, Western blotting, and enzyme-linked immunosorbent assay techniques. Bio chemical analysis revealed a translocation of p38 from the cytoplasm to the detergent-resistant cell fraction only upon stimulation with contact sen…

Kontaktallergie (V 58–V 65)

Detection of increased tyrosine phosphorylation in murine Langerhans cells after stimulation with contact sensitizers.

The signalling pathways in epidermal Langerhans cells (LC) during activation by contact sensitizers are poorly understood. Recently, we have described an increased phosphorylation of tyrosine residues in human MHC class II-positive cells in vitro following stimulation with contact sensitizers. In the study reported here the formation of phosphotyrosine (p-tyr) in murine epidermal LC upon stimulation with contact sensitizers was examined. By the use of a flow cytometric technique a significant increase in p-tyr was demonstrated in LC stimulated in vitro with the strong contact sensitizers TNCB (2,4,6-trinitro-chlorobenzene) and MCI/MI (5-chloro-2-methylisothiazolinone plus 2-methylisothiazol…