Immunology

Killer Cells for Killer Bacteria

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Science  30 Sep 2011:
Vol. 333, Issue 6051, pp. 1803
DOI: 10.1126/science.333.6051.1803-b

Natural killer T (NKT) cells are an unusual type of immune cell because they straddle the line between the innate and adaptive immune systems. They express an antigen receptor and require antigen presentation by a (nonclassical) major histocompatability complex molecule, but unlike most lymphocytes, they mount rapid responses to infection. Although shown to participate in immune responses to a wide variety of infections, a ligand from a highly pathogenic organism, which might explain the evolutionary conservation of NKT cells, and its invariant antigen receptor in particular, has not been identified. Kinjo et al. now report that NKT cells from both mice and humans are able to recognize diacylglycerol- containing glycolipids from Streptococcus pneumonia and group B Streptococcus, both of which can cause fatal infections in humans. The response to these glycolipids was dependent on the presence of vaccenic acid, which is expressed at low levels in mammalian cells and therefore might help NKT cells distinguish these microbes as foreign.

Nat. Immunol. 12, 996 (2011).

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