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

The Human Leukocyte Antigen (HLA) class I and II peptide-binding groove is the specialized structural domain of Major Histocompatibility Complex (MHC) molecules responsible for anchoring and presenting processed peptide fragments to T-cell receptors (TCRs). Class I grooves, formed by the alpha-1 and alpha-2 domains, typically bind short endogenous peptides (8-10 amino acids) to activate CD8+ cytotoxic T cells (Neefjes et al., 2011, Nature Reviews Immunology). Class II grooves, formed by the alpha-1 and beta-1 domains, accommodate longer exogenous peptides (13-25 amino acids) to activate CD4+ helper T cells (Rock et al., 2016, Chemical Reviews). This site is a fundamental determinant of immune specificity and plays a central role in immune surveillance, autoimmunity, and transplant rejection. In pharmacology, the groove is a target for peptide-based vaccines and TCR-mimetic antibodies designed to direct immune responses against specific tumor or viral antigens. Furthermore, certain small-molecule drugs can bind non-covalently within the groove, altering the repertoire of presented self-peptides and triggering severe idiosyncratic hypersensitivity reactions, such as those observed with Abacavir in HLA-B*57:01-positive individuals (Illing et al., 2012, Nature; Chung et al., 2014, Nature).

Other names

MHC peptide-binding cleftHLA binding pocketMajor Histocompatibility Complex peptide-binding grooveAntigen-binding grooveMHC binding site

Altered peptide repertoire model, pharmacological interaction with immune receptors (p-i) model, competitive peptide binding, stabilization of the HLA-peptide complex, and direct TCR-mimetic binding.