Specific and non-specific pathways to the cellular uptake of beta-lactoglobulin, a major food allergen

Beta-lactoglobulin (BLG) is abundant in bovine whey and is a major food allergen. The physiological consequences of technological treatments of BLG are much debated, also because multiple mechanisms seem to be involved in BLG recognition and uptake. Since food protein allergens are consumed in the presence of other food components, we aimed at understanding the consequences of conformational changes ensuing from the interaction of BLG with hydrophobic interfaces (such as oil-in-water emulsions), and how these can affect its capability of binding to specific antibodies, to be taken up by cells, and to activate response by cells of the immune human system. BLG increases its immunoreactivity after interaction with the interface, and affinity of interface-bound BLG towards specific monoclonal antibodies remains high after trypsin hydrolysis, at least when compared with the protein hydrolyzed in solution. However, the physical state of BLG does not influence the rate of its uptake by antigen presenting cells, e.g. monocytes, but competition experiments indicate that different uptake pathways seem to be operate operating for free and interface-bound BLG. These results highlight the importance of the protein physical state with respect to physiologically relevant properties, with significant practical implications. MM and MM are the grateful recipients of postdoctoral fellowships from the University of Milan. A stay of RGB in Denmark was made possible by the Erasmus-Placement program.