pMHCbased

pMHCbased refers to approaches and reagents that rely on peptide-major histocompatibility complex (pMHC) molecules to study T cell recognition and function. In these systems, specific peptide epitopes are loaded into MHC molecules and presented on cell surfaces or in soluble form as pMHC complexes. The primary applications are to identify and characterize antigen-specific T cells, monitor immune responses, and enable isolation of T cells for research or therapeutic purposes. pMHCbased methods apply to both major T cell subsets: MHC class I–restricted CD8+ T cells and MHC class II–restricted CD4+ T cells.

Key reagents include soluble pMHC monomers and multimeric complexes such as tetramers and dextramers, typically formed through biotin-streptavidin linking. These multimers bind antigen receptors with higher avidity, allowing detection by flow cytometry. Proper peptide loading, MHC allele matching, and complex stability are critical, and false positives can arise from non-specific binding at high avidity or elongated binding kinetics. Limitations include dependence on TCR affinity, potential peptide exchange, and the need for quality control controls and known HLA restrictions.

Applications span immune monitoring in infectious diseases and vaccination, cancer immunotherapy, and basic T cell biology. pMHCbased assays support enumeration of epitope-specific T cell frequencies, isolation of rare clones for sequencing or TCR discovery, and evaluation of T cell responses in clinical trials. Advances include alternative multimer formats, improved peptide loading methods, and integration with single-cell analyses to link TCR sequences with transcriptional profiles.