Models for Ves v 5 processing and the presentation of allergenic and epitopes. Stable protein segments are shaded. For clarity, only three stable segments are illustrated. Presentation of the deep epitope (upper pathway) requires an initial cleavage that yields a proteolytic fragment whose N-terminal end binds to the MHCII. In the course of DM-catalyzed dissociation and rebinding, the fragment unfolds and optimizes interaction with the MHCII binding site. Presentation of the shallow epitope (lower pathway) is similar; except that an initial cleavage is not required before MHCII binding, and no significant unfolding occurs during DM-catalyzed dissociation and rebinding. Proteolytic trimming of the MHCII-bound fragments yield MHCII-peptide complexes that traffic to the surface of the APC.