Editors' ChoiceImmunology

Recognition Receptor Revealed

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Science Signaling  30 Sep 2008:
Vol. 1, Issue 39, pp. ec343
DOI: 10.1126/scisignal.139ec343

In jawed vertebrates, immunoglobulin genes undergo recombination of variable, diverse, and joining gene segments to give a wide diversity of antibodies that recognize foreign antigens. The mechanism for antigen recognition in jawless vertebrates is quite different, involving variable lymphocyte receptors (VLRs) that achieve diversity by combinatorial assembly of leucine-rich repeat (LRR) gene cassettes. The structural basis for antigen specificity has been well studied for immunoglobulins, but the mode of antigen recognition by VLRs had not been determined. Now Han et al. have determined the crystal structure of a lamprey VLR bound to antigen. The VLR forms a solenoid structure, and the antigen is bound to the concave surface that contains variable regions of LRR sequence. A variable loop in the carboxyl-terminal module also plays a role in recognition. VLRs structurally resemble Toll-like receptors (TLRs) that play specialized roles in pathogen recognition in the mammalian innate immune system; however, we will have to await more structures of VLR and TLR complexes to clarify their evolutionary relationship.

B. W. Han, B. R. Herrin, M. D. Cooper, I. A. Wilson, Antigen recognition by variable lymphocyte receptors. Science 321, 1834-1837 (2008). [Abstract] [Full Text]

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