Abstract
Pollen allergy is characterized by a TH2-biased immune response to pollen-derived allergens. However, pollen-exposed epithelia do not encounter pure allergen but rather a plethora of protein and non-protein substances. We demonstrated that pollen liberate lipids with chemical and functional similarities to leukotriens and prostaglandins - the pollen associated lipid mediators (PALMs). To date, two main groups of PALMs have been characterized: The immunostimulatory PALMs activating innate immune cells such as neutrophils and eosinophils, and the immunomodulatory E1-phytoprostanes blocking IL-12 production of dendritic cells, resulting in the preferential induction of TH2 responses. This article reviews our work in the field of PALMs and their effects on cells of the innate and adoptive immune system. From recent results a general picture starts to emerge in which PALMs (and possibly other pollen-associated substances) may - independently from protein allergens - propagate an overall TH2 favoring micromilieu in pollen exposed tissue of predisposed individuals.
Highlights
Atopic diseases are characterized by a predominance of T helper cell type 2 (TH2) biased immune responses to environmental allergens
The trafficking of immature dendritic cell (DC) to sites of inflammation and of mature DCs to the T cell area of secondary lymphoid organs is regulated by the expression of different chemokines and chemokine receptors [6]
pollenassociated lipid mediator (PALM) confer a TH2 promoting phenotype on DCs. Apart from their effects on neutrophils and eosinophils we investigated the impact of PALMs on human dendritic cells - the initiators of T cell responses
Summary
Atopic diseases are characterized by a predominance of T helper cell type 2 (TH2) biased immune responses to environmental allergens. DCs matured in the presence of aqueous pollen extracts respond by releasing TH2 attracting chemokines and aquire a distinct migratory phenotype. Since arachidonic acid metabolites are well known to affect human innate and adaptive immune responses we were prompted to further investigate the effects of aqueous pollen extracts and their constituents.
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