Induction of Direct Antimicrobial Activity Through Mammalian Toll-Like Receptors

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Science  23 Feb 2001:
Vol. 291, Issue 5508, pp. 1544-1547
DOI: 10.1126/science.291.5508.1544

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The mammalian innate immune system retains fromDrosophila a family of homologous Toll-like receptors (TLRs) that mediate responses to microbial ligands. Here, we show that TLR2 activation leads to killing of intracellular Mycobacterium tuberculosis in both mouse and human macrophages, through distinct mechanisms. In mouse macrophages, bacterial lipoprotein activation of TLR2 leads to a nitric oxide–dependent killing of intracellular tubercle bacilli, but in human monocytes and alveolar macrophages, this pathway was nitric oxide–independent. Thus, mammalian TLRs respond (asDrosophila Toll receptors do) to microbial ligands and also have the ability to activate antimicrobial effector pathways at the site of infection.

  • * These authors contributed equally to this work.

  • To whom correspondence should be addressed. E-mail: rmodlin{at}

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