Post-Translational Modification Impact on MHC Peptide Binding and TCR Engagement

The human major histocompatibility complex (MHC) plays a crucial role in the presentation of peptidic fragments from proteins in the cytosol; these peptides can be derived from self-proteins or from non-human antigens, such as those produced by viruses or bacteria. To prevent cytotoxicity against healthy cells, thymocytes expressing T-cell receptors (TCRs) that recognize self-peptides are removed from circulation in a process called negative selection. However, post-translational modifications (PTMs) are excluded from negative selection; this feature opens the door to the possibility that PTMs directly contribute to the development of autoreactive T-cells and subsequent autoimmune disease. Despite it being well-established that PTMs are prevalent in peptides presented on MHCs, the exact mechanisms by which PTMs influence the antigen presentation machinery remains poorly understood. In this study, we introduce chemical modifications mirroring PTMs onto peptides to systematically investigate their impact on MHC binding and TCR recognition. Our findings reveal the numerous ways PTMs alter antigen presentation, which could have implications for tumor neoantigen presentation. ### Competing Interest Statement The authors have declared no competing interest.