It has been over 40 years since it was discovered that the major histocompatibility (MHC) class I molecules present peptides for the CD8 T cell-mediated immune response. The pathways for delivering and processing peptides for the MHC class I complexes have since been thoroughly studied but it is only until more recently that we start to understand the mechanisms that provide peptide material for the endogenous MHC class I pathway. Interestingly, the main source of antigenic peptide substrates does not come from the same mRNA translation mechanism that produces full length proteins but from ribosomes which products sole purpose might be to produce antigenic peptide substrates. We will discuss the latest development in this field and its implications for a better understanding of one of the corner stones for how the immune system distinguishes between self and non-self.
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