Editing peptide presentation to T cells

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Science  24 Nov 2017:
Vol. 358, Issue 6366, pp. 992-993
DOI: 10.1126/science.aaq1398

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In mammals, two types of major histocompatibility complex (MHC) molecules, MHC I and MHC II, are found on the surface of cells in association with peptides. If these peptides are antigenic—that is, if they induce an immune response—the resulting MHC I–peptide complexes are recognized by CD8+ T cells, which are effector immune cells, whereas MHC II-peptide complexes are recognized by CD4+ T cells, which facilitate both humoral and cellular immune responses. MHC I and MHC II clasp the peptides in a binding groove consisting of two antiparallel α helices that overlay an eight-stranded β sheet. On pages 1064 and 1060 of this issue, Jiang et al. (1) and Thomas and Tampé (2) reveal how peptide binding to MHC I molecules is regulated.