Peptide–human leukocyte antigen complex (Peptide–HLA complex)

The **peptide–human leukocyte antigen (HLA) complex** is a molecular assembly formed when short antigenic peptides, derived from viral, tumor, or self proteins, are bound and presented on the surface of cells by HLA (major histocompatibility complex, MHC) proteins. These complexes are essential for immune surveillance, allowing T cells to distinguish between healthy cells and those infected by viruses or transformed by cancer[1][2][5]. There are two main classes: **MHC class I peptide–HLA complexes**, which present intracellular antigens to CD8+ cytotoxic T cells (critical for recognition of virus-infected cells), and **MHC class II peptide–HLA complexes**, which present antigens to CD4+ helper T cells[1]. The structure and specificity of the peptide–HLA complex determines T cell activation and downstream immune response. These complexes serve as key therapeutic targets for immunotherapies (such as engineered T cell therapies, bispecific engagers, and checkpoint inhibitors) by exploiting or enhancing T cell recognition of disease-specific antigens displayed by infected or cancerous cells[5][6]. The diversity and allelic variability of HLA molecules underlies their clinical relevance in infection, cancer, and transplantation[1][2][3][5].

Other names

Peptide–MHC complexPeptide–major histocompatibility complexpMHCHLA–peptide complexPeptide–MHC class I/II complex

Recognition and targeting of specific peptide–HLA complexes by engineered T cell receptors or bispecific molecules; Enhancement of immune response via immune checkpoint blockade