Tumor antigen–Major Histocompatibility Complex class I complex (pMHC-I)

Tumor antigen–Major Histocompatibility Complex (MHC) class I complexes are the fundamental units of recognition for the adaptive cellular immune system, specifically CD8+ cytotoxic T lymphocytes. These complexes consist of a proteolytically derived peptide fragment, typically 8-11 amino acids in length, derived from tumor-associated antigens or neoantigens, nested within the binding groove of an MHC class I molecule (HLA in humans) [Janeway's Immunobiology, 9th edition]. This presentation mechanism allows the immune system to monitor the intracellular proteome for abnormalities, such as somatic mutations or the aberrant expression of germline genes like MAGE-A4 or NY-ESO-1. In therapeutic contexts, these complexes are targeted by engineered T-cell receptor (TCR) therapies and bispecific proteins to induce potent, tumor-specific lysis [PMID: 34551229]. The clinical success of targeting these complexes is highly dependent on the patient's specific HLA genotype and the stable expression of the target peptide on the tumor surface. However, a significant challenge remains the potential for lethal cross-reactivity if the therapeutic TCR recognizes similar peptides presented on vital healthy organs [PMID: 23770511].

Other names

Peptide-MHC complexpMHCpHLATumor-associated antigen-MHC complexNeoantigen-MHC complexMHC-peptide complexHLA-peptide complex

Therapeutic agents targeting these complexes, such as TCR-engineered T cells (TCR-T) or bispecific T-cell engagers (ImmTACs), utilize high-affinity T-cell receptors or TCR-like antibodies to bind the specific peptide-MHC complex on the tumor cell surface. This binding event triggers the formation of an immunological synapse, leading to the release of perforins and granzymes by the T cell, which induces apoptosis in the target tumor cell [PMID: 34551229, PMID: 38552654].