We seek to identify consensus sequences in digested fragments of antigenic proteins regulating selection and major histocompatibility complex (MHC)-restricted presentation to T cells of epitopes within those fragments. One such pattern, of recurrent, hydrophobic sidechains forming a longitudinal hydrophobic strip when a sequence is coiled as an alpha-helix, is found in or near most T cell-presented epitopes. Such recurrent hydrophobicity may lead to protease-protected coiling of the fragment against endosomal membranes and transfer to MHC molecules. This concept leads to better identification of T cell-presented sequences and possible to engineering of T cell-presented vaccines to affect their potency and MHC restriction.