Major histocompatibility complex class II–restricted CD4-positive T cell receptor complex (MHC class II–CD4+ TCR complex (or MHC II–CD4+ TCR))

The Major histocompatibility complex class II–restricted CD4-positive T cell receptor complex is formed when an antigen-presenting cell displays a peptide antigen via MHC class II molecule, and a CD4+ T cell recognizes the peptide-MHC II complex through its T cell receptor (TCR), assisted by its surface CD4 co-receptor[2][3][6][7]. This multi-protein interface stabilizes the interaction, allowing signal transduction into the T cell—a pivotal step for T cell activation and subsequent adaptive immune responses[5][7]. The CD4 molecule binds to invariant regions of MHC class II, not the TCR, and brings Lck kinase close to the TCR-CD3 complex to initiate signaling[2][7]. This interaction is central to immune modulation, targeted by drugs in autoimmune disease, transplantation, and infectious disease management. It is also exploited by HIV, which binds CD4 to enter and destroy helper T cells, leading to immune deficiency[1]. Mutations, genetic polymorphisms, or therapeutic interventions affecting any part of this complex have major implications for disease susceptibility and immunotherapy outcomes.

Other names

MHC II–restricted TCR–CD4 complexpMHCII–TCR–CD4 complexMHC class II–CD4+ T cell interactionMHC II–TCR signaling complex

Blockade/inhibition of CD4 binding (prevents antigen recognition or HIV infection); Immunosuppression (preventing TCR signaling and T cell activation); Modulation of T cell subset differentiation; Preventing co-receptor-mediated Lck recruitment and signal amplification