Human leukocyte antigen A2 class I major histocompatibility complex molecule (HLA-A2)

HLA-A2 is a class I major histocompatibility complex (MHC) molecule found on virtually all nucleated human cells and platelets. It consists of a polymorphic α chain encoded within the HLA region on chromosome 6, and a non-polymorphic β2 microglobulin. The α chain presents short peptide antigens (typically 8–10 amino acids) within its peptide-binding groove formed by α1 and α2 domains. These peptide complexes are recognized by CD8+ T cell receptors, initiating cytotoxic immune responses against infected or malignant cells. HLA-A2 is highly polymorphic, affecting antigen presentation and immune recognition diversity. It serves as a critical determinant for immune activation, tumor surveillance, infection control, and transplant compatibility. The structure of HLA-A2 is a prototypical reference in immunology; its crystal structure was first determined in 1989, unveiling a conserved fold among MHC class I molecules. HLA-A2 is especially prominent in cancer immunotherapy as a presenting molecule for numerous tumor antigens and neoantigens, guiding patient selection for targeted therapies and vaccines. It is also central to transplant immunology, with mismatches contributing to rejection and GVHD.

Other names

HLA-A2MHC class I HLA-A2Human major histocompatibility complex class I antigen HLA-A2A*02:01HLA class I A2

Facilitation of immune recognition of peptide antigens by T cell receptors (TCRs) on CD8+ T cells; Triggering cytotoxic response leading to target cell lysis; Modulating immune cell activation or tolerance depending on presented peptide; Blocking or enhancing peptide binding/cellular presentation