Patient-specific tumor antigen-major histocompatibility complex (pMHC)

Patient-specific tumor antigen-major histocompatibility complexes (pMHC) are the primary targets for cellular immunotherapies, including Tumor-Infiltrating Lymphocyte (TIL) therapy and TCR-engineered T-cell therapy. These complexes are formed when intracellular proteins, particularly those containing tumor-specific mutations known as neoantigens, are degraded into peptides and presented on the cell surface by Major Histocompatibility Complex (MHC) molecules [Rosenberg, 2015, Science]. The specificity of the immune response is determined by the interaction between these pMHC complexes and the T-cell receptors (TCRs) found on the surface of T-lymphocytes [Tran, 2014, Science]. In therapeutic applications, TILs are harvested from a patient's tumor, expanded ex vivo to increase the population of T-cells recognizing these specific pMHCs, and then re-infused into the patient [NCI, 2024]. This interaction triggers a cytotoxic cascade, involving the release of perforins and granzymes, which leads to the programmed death of the tumor cell [Abbas, 2021, Cellular and Molecular Immunology]. While highly effective for certain solid tumors, the success of targeting pMHCs depends on the stable expression of MHC molecules and the absence of cross-reactivity with similar peptides presented on healthy tissues [Yee, 2022, Nature Reviews Clinical Oncology]. Drugs like Lifileucel utilize this mechanism by providing a massive dose of T-cells pre-selected for their ability to recognize these unique patient-specific markers [FDA, 2024]. Challenges include the high degree of polymorphism in HLA genes and the ability of tumors to escape immune pressure by downregulating antigen presentation machinery [Garrido, 2016, Cancer Immunology, Immunotherapy].

Other names

Neoantigen-MHC complexTumor-specific antigen-HLA complexNeoepitope-MHC complexpMHC complexTumor peptide-MHC complex

The mechanism involves the specific binding of a T-cell receptor (TCR) to a peptide-MHC complex, which initiates signal transduction through the CD3 complex and results in the activation of cytotoxic T-lymphocytes to induce apoptosis in the target cell [Abbas, 2021, Cellular and Molecular Immunology].