Biology Reference
In-Depth Information
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6 hrs
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C57BL/6j
CBA/Ca
Day post infection
Liver
Lungs
FIGURE 5.2
Changes in the mean larval burden (
S.E.M.) in the liver and lungs in
C57BL/6j and CBA/Ca mice, following inoculation with 1000 Ascaris suum larvae.
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environment in the lung mucosa, and genetic variation in host response
at this level may influence the subsequent course of adult worm
infection.
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As stated above, C57BL mice appear to be considerably more suscep-
tible to Ascaris larval infection than any of the other strains tested and in
contrast to all the other mouse strains tested are known also to lack the
Itln-2 gene which has been linked with expulsion of intestinal stages of
Trichinella spiralis and Trichuris muris.
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e
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This suggested a simple genetic
explanation for their greater susceptibility to migrating larvae and
inability to control infection at the liver stage, but breeding experiments
based on F
1
crosses between C57BL/6j and CBA/Ca mice, and F
2
back-
crosses to both parental strains found no evidence that susceptibility
segregated with absence of this gene and resistance increased with the
number of copies of the Itln-2 gene.
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The unusually high susceptibility of
C57BL mice therefore still warrants explanation.
As Mitchell et al. found,
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mice show acquired resistance to infection
and greater numbers of lesions have been observed with more larvae
surrounded by inflammatory cells in experimentally-infected mice and
