Peptide–HLA complex (pHLA complex)

A peptide–HLA complex is a **cell-surface complex formed by a peptide (typically 8–15 amino acids) bound within the peptide-binding groove of a Human Leukocyte Antigen (HLA) molecule**. HLA molecules—classified as class I (HLA-A, -B, -C) and class II (HLA-DP, -DQ, -DR)—are responsible for the presentation of processed peptide antigens to T-cell receptors (TCRs) on T lymphocytes[2][3][4][5]. The peptide-binding groove of the HLA molecule contains specific pockets that determine the selectivity for peptide side chains, and the resulting complex (peptide-HLA or pHLA) is recognized by TCRs, which triggers immune responses including cytotoxicity toward infected or malignant cells[2][3][6]. pHLA complexes are highly polymorphic due to HLA gene diversity and regulate the range of presented antigens; they have become central therapeutic targets for engineered T-cell and TCR-mimic antibody therapies, as well as for diagnostic purposes in infection, cancer, and autoimmunity[4][6]. Therapeutic targeting of pHLA can be challenging due to cross-reactivity and safety risks, but offers potentially high selectivity for diseased cells by recognizing unique or neoantigen-derived peptide–HLA complexes[4][6].

Other names

peptide–MHC complexpMHC complexpeptide–major histocompatibility complex complexpeptide–HLA-I complex (for class I)peptide–HLA-II complex (for class II)

Direct targeting by T-cell receptor (TCR)-mimic biologics: drugs bind specific peptide–HLA complexes on cell surfaces to mediate immune responses, often cytotoxicity in presence of T-cells[4]. Redirection of T-cell activity by bispecific antibodies: these drugs bridge effector T-cells to cells presenting specific pHLA complexes, leading to cell killing. Activation or modulation of immune recognition by targeting the presented peptide repertoire for vaccine approaches. Selective depletion/introduction of peptide–HLA complexes by small molecules for immune evasion or tolerance (experimental).