Human leukocyte antigen class I and class II peptide-binding groove (HLA-I/II peptide-binding groove)

The Human Leukocyte Antigen (HLA) class I and class II peptide-binding grooves are specialized structural domains located on the surface of Major Histocompatibility Complex (MHC) molecules. These grooves are responsible for capturing and presenting short peptide fragments—derived from endogenous proteins in Class I or exogenous pathogens in Class II—to T-cell receptors (TCRs) to initiate adaptive immune responses (StatPearls, 2023). The highly polymorphic nature of the amino acid residues lining these grooves determines the specific repertoire of peptides an individual can present, which is fundamental to immune surveillance and self/non-self discrimination (UniProt). In clinical pharmacology, these grooves are the primary site for idiosyncratic drug hypersensitivity reactions; small molecule drugs like abacavir can bind directly within the groove of specific HLA alleles (e.g., HLA-B*57:01), altering the peptide-binding specificity and triggering an autoimmune-like T-cell attack (Nature, 2012). Additionally, the peptide-binding groove is a major target for therapeutic development, including peptide vaccines for cancer and competitive inhibitors like glatiramer acetate used to treat multiple sclerosis by displacing myelin-derived antigens (PubMed, 2021).

Other names

MHC peptide-binding cleftHLA antigen-binding pocketMHC class I and II binding groovesHLA-peptide binding site

Drugs can bind non-covalently within the peptide-binding groove, altering the chemical environment and shape of the pocket. This 'altered repertoire' mechanism causes the HLA molecule to present a different set of self-peptides (neo-antigens) to T-cells, triggering hypersensitivity. Other drugs, like glatiramer acetate, act as competitive inhibitors that displace specific pathogenic peptides from the groove to modulate autoimmune responses.