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J. Exp. Med.,
Volume 189, Number 4, February 15, 1999 615-625
By







From the * Department of Medicine, Bacterial lipopolysaccharide (LPS) provokes a vigorous, generalized proinflammatory state in
the infected host. Genetic regulation of this response has been localized to the Lps locus on
mouse chromosome 4, through study of the C3H/HeJ and C57BL/10ScCr inbred strains.
Both C3H/HeJ and C57BL/10ScCr mice are homozygous for a mutant Lps allele (Lpsd/d) that
confers hyporesponsiveness to LPS challenge, and therefore exhibit natural tolerance to its lethal effects. Genetic and physical mapping of 1,345 backcross progeny segregating this mutant
phenotype confined Lps to a 0.9-cM interval spanning 1.7 Mb. Three transcription units were
identified within the candidate interval, including Toll-like receptor 4 (Tlr4), part of a protein
family with members that have been implicated in LPS-induced cell signaling. C3H/HeJ mice
have a point mutation within the coding region of the Tlr4 gene, resulting in a nonconservative substitution of a highly conserved proline by histidine at codon 712, whereas C57BL/
10ScCr mice exhibit a deletion of Tlr4. Identification of distinct mutations involving the same
gene at the Lps locus in two different hyporesponsive inbred mouse strains strongly supports
the hypothesis that altered Tlr4 function is responsible for endotoxin tolerance.
Department of Biochemistry, and § Department of Human
Genetics, McGill University, Montreal, Quebec, Canada H3G 1A4; the
Centre for the Study of
Host Resistance, Montreal General Hospital, Montreal, Quebec, Canada H3G 1A4; and ¶ Millennium Pharmaceuticals, Inc., Cambridge, Massachusetts 02139
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