Human leukocyte antigen class I - CD8 alpha complex (HLA-I/CD8α)

The HLA class I via CD8α co-receptor interaction is a fundamental component of the adaptive immune system, specifically governing the activation and effector functions of cytotoxic T lymphocytes (CTLs). Human Leukocyte Antigen (HLA) class I molecules (UniProt P01889) present endogenous peptides on the surface of almost all nucleated cells, while the CD8α co-receptor (UniProt P01732), typically expressed on CTLs, binds to the non-polymorphic α3 domain of the HLA class I heavy chain [1, 2]. This binding event stabilizes the TCR-pMHC (T-cell receptor-peptide-MHC) complex and facilitates the recruitment of the tyrosine kinase Lck to the TCR-CD3 complex, which is essential for initiating the signaling cascade required for T-cell activation and subsequent lysis of target cells [2, 3]. In the context of disease, many tumors downregulate HLA class I expression to evade immune detection, while chronic infections can lead to T-cell exhaustion where this interaction is impaired [4]. Therapeutic strategies targeting this axis include the development of CD8-targeted imaging agents like IAB22M2C to monitor immune responses and engineered proteins or antibodies designed to enhance or restore the stability of the HLA-CD8 interaction to improve anti-tumor immunity [5, 6].

Other names

MHC class I - CD8 interactionHLA-I/CD8a complexCD8-MHC I axisCD8a-HLA-I complex

Stabilization of the T-cell receptor (TCR) engagement with the peptide-MHC complex and recruitment of Lck kinase to the CD3 complex to initiate downstream signaling for T-cell activation.