The Glycosylation Pattern of Common Allergens: The Recognition and Uptake of Der p 1 by Epithelial and Dendritic Cells Is Carbohydrate Dependent

Allergens are initiators of both innate and adaptive immune responses. They are recognised at the site of entry by epithelial and dendritic cells (DCs), both of which activate innate inflammatory circuits that can collectively induce Th2 immune responses. In an attempt to have a better understanding of the role of carbohydrates in the recognition and uptake of allergens by the innate immune system, we defined common glycosylation patterns in major allergens. This was done using labelled lectins and showed that allergens like Der p 1 (Dermatophagoides pteronyssinus group 1), Fel d 1 (Felis domisticus), Ara h 1 (Arachis hypogaea), Der p 2 (Dermatophagoides pteronyssinus group 2), Bla g 2 (Blattella germanica) and Can f 1 (Canis familiaris) are glycosylated and that the main dominant sugars on these allergens are 1–2, 1–3 and 1–6 mannose. These observations are in line with recent reports implicating the mannose receptor (MR) in allergen recognition and uptake by DCs and suggesting a major link between glycosylation and allergen recognition. We then looked at TSLP (Thymic Stromal Lymphopoietin) cytokine secretion by lung epithelia upon encountering natural Der p 1 allergen. TSLP is suggested to drive DC maturation in support of allergic hypersensitivity reactions. Our data showed an increase in TSLP secretion by lung epithelia upon stimulation with natural Der p 1 which was carbohydrate dependent. The deglycosylated preparation of Der p 1 exhibited minimal uptake by DCs compared to the natural and hyperglycosylated recombinant counterparts, with the latter being taken up more readily than the other preparations. Collectively, our data indicate that carbohydrate moieties on allergens play a vital role in their recognition by innate immune cells, implicating them in downstream deleterious Th2 cell activation and IgE production

Should digestion assays be used to estimate persistence of potential allergens in tests for safety of novel food proteins?

Food allergies affect an estimated 3 to 4% of adults and up to 8% of children in developed western countries. Results from in vitro simulated gastric digestion studies with purified proteins are routinely used to assess the allergenic potential of novel food proteins. The digestion of purified proteins in simulated gastric fluid typically progresses in an exponential fashion allowing persistence to be quantified using pseudo-first-order rate constants or half lives. However, the persistence of purified proteins in simulated gastric fluid is a poor predictor of the allergenic status of food proteins, potentially due to food matrix effects that can be significant in vivo. The evaluation of the persistence of novel proteins in whole, prepared food exposed to simulated gastric fluid may provide a more correlative result, but such assays should be thoroughly validated to demonstrate a predictive capacity before they are accepted to predict the allergenic potential of novel food proteins

Different initiation of pre-TCR and γδTCR signalling

International audienceLineage choice is of great interest in developmental biology. In the immune system, the alphabeta and gammadelta lineages of T lymphocytes diverge during the course of the beta-, gamma- and delta-chain rearrangement of T-cell receptor (TCR) genes that takes place within the same precursor cell and which results in the formation of the gammadeltaTCR or pre-TCR proteins. The pre-TCR consists of the TCRbeta chain covalently linked to the pre-TCRalpha protein, which is present in immature but not in mature T cells which instead express the TCRalpha chain. Animals deficient in pre-TCRalpha have few alphabeta lineage cells but an increased number of gammadelta T cells. These gammadelta T cells exhibit more extensive TCRbeta rearrangement than gammadelta T cells from wild-type mice. These observations are consistent with the idea that different signals emanating from the gammadeltaTCR and pre-TCR instruct lineage commitment. Here we show, by using confocal microscopy and biochemistry to analyse the initiation of signalling, that the pre-TCR but not the gammadeltaTCR colocalizes with the p56lck Src kinase into glycolipid-enriched membrane domains (rafts) apparently without any need for ligation. This results in the phosphorylation of CD3epsilon and Zap-70 signal transducing molecules. The results indicate clear differences between pre-TCR and gammadeltaTCR signalling