Transplants from Pigs

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Science  03 Dec 1999:
Vol. 286, Issue 5446, pp. 1853
DOI: 10.1126/science.286.5446.1853f

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The adaptive immune response is stimulated when peptides bound to major histocompatibility complex (MHC) molecules bind to T cells. Structures of T cell receptors (TCRs) in complex with peptide-MHC class I ligands have been determined. Now Reinherz et al. (p. 1913) present the structure of a TCR binding to a complex of a 16-residue peptide antigen and a murine MHC class II molecule (pMHCII). The authors propose that the angle of TCR-pMHCII docking will be restricted to a more "orthogonal" interaction than that seen in the class I "diagonal" mode, and that this difference in docking specifies the preferential binding of pMHCI and pMHCII to CD8 or CD4 co-receptors, respectively. In a Perspective, Wilson analyzes the similarities and differences between the pMHCII and pMHCI structures, and cautions that while this work is a valuable contribution, more TCR-pMHC structures are needed to understand fully the structural basis of TCR-MHC recognition.