T-cell receptor (TCR)

Each T cell carries T-cell receptors of a single specificity. When a TCR encounters a pMHC complex it fits, the T cell activates — proliferating and, for killer T cells, destroying the displaying cell.

Predicting which TCRs recognize which pMHCs (“TCR–pMHC” prediction) is one of the hardest open problems in immunology and a frontier for deep learning, because it determines whether a presented neoantigen actually triggers a response rather than just being displayed.