Major histocompatibility complex class I-peptide complex (pMHC-I)

The Major Histocompatibility Complex class I (MHC-I) peptide complex is a fundamental component of the adaptive immune system, responsible for displaying intracellular protein fragments on the cell surface for surveillance by CD8+ T-cells. These complexes consist of a polymorphic heavy chain, a light chain (beta-2 microglobulin), and a short antigenic peptide, typically 8 to 10 amino acids in length, derived from endogenous proteins. In healthy cells, these peptides represent 'self,' but in the context of infection or malignancy, they present viral or mutated 'neoantigenic' sequences that trigger a cytotoxic immune response. This mechanism is a primary target for modern immunotherapy, including TCR-engineered T-cells and bispecific T-cell engagers like Tebentafusp, which are designed to recognize specific pMHC-I targets on tumor cells. The therapeutic challenge lies in the high specificity required to avoid cross-reactivity with similar self-peptides found in healthy tissues, which can lead to severe adverse events. Furthermore, tumors often evolve to downregulate MHC-I expression as a method of immune evasion, making the restoration or bypass of this presentation pathway a key area of oncological research.

Other names

Antigenic peptides presented by MHC class I moleculesHLA-peptide complexMHC-I restricted antigenT-cell epitopepMHC

T-cell receptor (TCR) binding and activation of CD8+ cytotoxic T-lymphocytes to induce targeted cell lysis.