Defining cross presentation for a wider audience

Cross presentation is the process of production of peptide-MHC Class I complexes by cells in which the antigen that is the source of peptide is not translated. The majority of recent studies have described many facets of the classical TAP-dependent cross presentation pathway, but numerous pathways for transfer of antigenic material from a donor to a recipient cell followed by subsequent MHC-I-restricted presentation have been established, including transfer of protein antigen, peptide, RNA, DNA or even peptide-MHC-I complexes. The extent to which each of these pathways generates overlapping or unique peptide repertoires is unknown, as is the contribution of each of these pathways to generation of protective CD8+ T cells during infection or anti-tumor immune responses.