MHCpeptide

MHCpeptide refers to a peptide that is bound by a Major Histocompatibility Complex (MHC) molecule as part of antigen presentation to T cells. In vertebrates, MHC molecules are highly polymorphic cell-surface glycoproteins encoded by the MHC (known as HLA in humans) gene complex. Peptides are generated from proteins inside the cell or in endosomal pathways and are then loaded onto MHC molecules for display on the cell surface.

MHC class I peptides are typically derived from intracellular proteins and are loaded in the endoplasmic reticulum after proteasomal processing and transport by TAP. They are presented to CD8+ cytotoxic T cells. MHC class II peptides originate from extracellular or endocytosed proteins that are processed in lysosomal compartments and loaded onto MHC II molecules in endosomes, where they are displayed to CD4+ helper T cells. The loading and stability of MHCpeptides depend on chaperones and accessory molecules such as tapasin for class I and HLA-DM for class II.

The diversity of MHCpeptides is driven by MHC polymorphism, the range of proteolytic enzymes, and the repertoire of available antigens. The affinity and longevity of the MHCpeptide complex influence T cell recognition and the strength of the immune response. MHCpeptides are central to immune surveillance, vaccine design, transplant compatibility assessment, and cancer immunotherapy, where neoantigen-targeted strategies seek to elicit robust T cell responses. Advances in peptidomics and structural biology continue to map the landscape of MHC-bound peptides and their immunogenic potential.