A biological function for the XP motif within the N terminus of major histocompatibility complex class II‐associated peptides

摘要

AbstractA high proportion (up to 30) of major histocompatibility complex (MHC) class II‐bound peptides in the mouse and humans contains a proline residue at the N‐terminal penultimate position (XP motif). We used a set of ovalbumin (OVA)‐specific and hen egg lysozyme (HEL)‐specific T cell hybridomas and asked whether the XP motif in MHC class II‐associated peptides might influence the stimulation of T cells. We created N‐terminally substituted variants of OVA323–339, an H2‐Adrestricted OVA epitope and of HEL50–63, a dominant epitope in the context of H2‐Ak. Our results show that the N‐terminal sequence of MHC class II‐bound peptides has a strong impact for the overall stimulation of specific T cells. Proline at the N terminus of antigenic peptides, in contrast to other amino acids, is tolerated or even enhances the recognition of MHC class II‐bou