Th1-Zellen, Th2-Zellen und atopische Dermatitis

Der Hautarzt (Impact Factor: 0.54). 48(4):223-227. DOI: 10.1007/s001050050573

ABSTRACT Die zugunsten der Th2-Zellen verschobene Th1/Zh2-Balance ist ein wesentliches Charakteristikum der atopischen Dermatitis (AD).
Die Reaktion auf hochmolekulare Umweltallergene (z.B. Pollen, Hausstaubmilben), Produktion des IgE und Aktivierung von eosinophilen
Granulozyten sind Folge der Th2-Dominanz. Das Th2-Zytokin Interleukin-4 (IL-4) ist für die IgE-Synthese erforderlich. Außerdem
inhibiert IL-4 die Generierung von Th1-Zellen. Reziproke Eigenschaften besitzt das Markerzytokin der Th1-Zellen, das Interferon
γ (IFNγ). Es hemmt die IgE-Synthese und die Th2-Expansion, fördert aber das Th1-Zellwachstum. Während die Mechanismen IgE-mediierter
Soforttyp- Reaktionen schon länger bekannt sind, wurde die Bedeutung des IgE für die AD erst durch die Entdeckung von IgE-Rezeptoren
auf der Langerhans-Zelloberfläche wahrscheinlich gemacht. Vermutlich ist das Langerhans-Zell-gebundene IgE für die Präsentation
hochmolekularer Aeroallergene erforderlich. Th-Analysen zu unterschiedlichen Zeiten nach Allergenexposition zeigten, daß Th2-Zellen
offenbar in der Initialphase inflammatorischer Reaktionen eine wichtige Rolle spielen, während in späteren Phasen auch Th1-Zellen
in größerem Umfang nachgewiesen werden können.

The immunological hallmark of atopic dermatitis (AD) is a Th1/Th2 dysbalance. The reaction to high molecular weight environmental
allergens (e.g. pollen, house dust mites),production of IgE and activation of eosinophil granulocytes result from Th2 dominance.
The Th2-cytokine interleukin-4 (IL-4) is necessary for IgE synthesis. Additionally, IL-4 inhibits the generation of Th1-cells.
The marker cytokine of Th1-cells, interferon γ (IFNγ), exhibits reciprocal effects. It inhibits IgE synthesis and Th2 expansion,
but supports Th1-cell growth. Beside the well known mechanisms of IgE-mediated immediate type reactions, the relevance of
IgE for the pathogenesis of AD seems to be likely since the discovery of IgE-receptors upon Langerhans cell surfaces. Langerhans
cell-bound IgE may be possibly neccessary for the presentation of high molecular weight aero-allergens. Analyses of Th subsets
at different intervals after allergen challenge showed, that Th2-cells play an important role in the initial phase of inflammatory
reactions whereas in later stages Th1-cells can be detected in greater numbes.

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