FIG 4.

Processing and presentation of a dominant epitope and an I-A^k+ epitope that is concealed by a disulfide bond. Proteolytic cleavage makes the dominant epitope available for loading into the MHC protein. In the case of an intact disulfide bond (upper pathway), the I-A^k+ epitope remains unavailable for loading because the disulfide bond stabilizes the partially folded conformation. In the case of a mutated disulfide bond (lower pathway), the I-A^k+ epitope is presented because the protein undergoes additional unfolding.