T-cell receptor–Major Histocompatibility Complex class II protein–protein interface (TCR–MHC II interface)

The T-cell receptor–Major Histocompatibility Complex class II (TCR–MHC II) protein–protein interface is a critical molecular junction in the adaptive immune system, responsible for the recognition of exogenous antigens by CD4+ T helper cells (Roche & Furuta, 2015, Nat Rev Immunol). This interface forms when a TCR on a T cell binds to a peptide fragment presented by an MHC II molecule on the surface of an antigen-presenting cell (Hennecke & Wiley, 2001, Cell). The stability and affinity of this interaction determine the strength of the resulting T-cell signal, which orchestrates immune responses against pathogens or, in pathological states, against self-antigens (Rudolph et al., 2006, Annu Rev Immunol). Dysregulation or inappropriate activation at this interface is a hallmark of various autoimmune diseases, such as rheumatoid arthritis and multiple sclerosis, where T cells mistakenly attack host tissues (Wucherpfennig et al., 2010, Cold Spring Harb Perspect Biol). Consequently, the TCR–MHC II interface is a high-value therapeutic target for immunomodulatory drugs designed to either block the interaction or induce tolerance (Yin et al., 2012, J Clin Immunol). Current and emerging therapies include altered peptide ligands, MHC II-specific antibodies, and small molecules that disrupt the docking of the TCR to the pMHC II complex (DrugBank DB00644).

Other names

TCR-pMHCII complexTCR-HLA class II interactionAntigen-MHC II-TCR interfaceT-cell receptor-peptide-MHC class II complex

The mechanism of action involves the competitive inhibition of antigenic peptide binding to the MHC class II groove or the physical disruption of the TCR-MHC docking site, which prevents the formation of the immunological synapse and inhibits downstream T-cell activation and proliferation (DrugBank DB00644; Hennecke & Wiley, 2001, Cell).