Passage
Lipopolysaccharides (LPS) found in gram-negative bacterial cells can elicit a lethal degree of adjuvanticity, or immune activation, in LPS-responsive host organisms. In mice, responses may be modulated by abnormalities in the toll-like receptor (TLR) encoded by the Tlr4 gene closely linked to coat color on Chromosome 4. To investigate the effect of a particular Tlr4 mutation on LPS response, three experiments were performed following a cross between fully responsive He-N mice [tlr4(+) /tlr4(+) ] and He-J mice homozygous for the mutation [tlr4(d) /tlr4(d) ].Experiment 1Researchers isolated spleen cells for analysis of protein expression and LPS response. In cells isolated from F1 mice, both wild-type and mutant TLRs were distinguishable by protein electrophoresis. Following this first analysis, spleen cells from each cohort were exposed to 2 × 10⁵ SRC, an antigen formed by sheep erythrocytes. Cultures were then incubated in the presence or absence of Ph-LPS, with LPS extracted from Escherichia coli K345 cells using a phenol-water mixture. Titers of anti-SRC antibody were recorded on incubation day 5, with the results shown in Table 1.Table 1 Mean anti-SRC titers with standard error
Experiment 2Serum samples were assayed for interferon production 2 hours post LPS injection. Interferon was quantified using a plaque reduction assay on mouse cells challenged with vesicular stomatitis virus.
Figure 1 Average serum interferon levels in mice cohortsExperiment 3Mice were injected with varying doses of Ph-LPS and monitored for 4 days. The lethal dose (LD₅₀) was defined as the minimum dose causing death in 50% of injected mice. Compared to He-N mice, results reflected a 10-fold increase in LD₅₀ for F1 mice and a 100-fold increase in LD₅₀ for He-J mice.
-If researchers repeated the analyses using F2 generation mice, spleen cell cultures exposed to SRC plus 1.0 μg Ph-LPS would be expected to have anti-SRC titers of:16001200800

Question

Passage
Lipopolysaccharides (LPS) found in gram-negative bacterial cells can elicit a lethal degree of adjuvanticity, or immune activation, in LPS-responsive host organisms. In mice, responses may be modulated by abnormalities in the toll-like receptor (TLR) encoded by the Tlr4 gene closely linked to coat color on Chromosome 4. To investigate the effect of a particular Tlr4 mutation on LPS response, three experiments were performed following a cross between fully responsive He-N mice [tlr4(+) /tlr4(+) ] and He-J mice homozygous for the mutation [tlr4(d) /tlr4(d) ].Experiment 1Researchers isolated spleen cells for analysis of protein expression and LPS response. In cells isolated from F1 mice, both wild-type and mutant TLRs were distinguishable by protein electrophoresis. Following this first analysis, spleen cells from each cohort were exposed to 2 × 10⁵ SRC, an antigen formed by sheep erythrocytes. Cultures were then incubated in the presence or absence of Ph-LPS, with LPS extracted from Escherichia coli K345 cells using a phenol-water mixture. Titers of anti-SRC antibody were recorded on incubation day 5, with the results shown in Table 1.Table 1 Mean anti-SRC titers with standard error

Experiment 2Serum samples were assayed for interferon production 2 hours post LPS injection. Interferon was quantified using a plaque reduction assay on mouse cells challenged with vesicular stomatitis virus.

Figure 1 Average serum interferon levels in mice cohortsExperiment 3Mice were injected with varying doses of Ph-LPS and monitored for 4 days. The lethal dose (LD₅₀) was defined as the minimum dose causing death in 50% of injected mice. Compared to He-N mice, results reflected a 10-fold increase in LD₅₀ for F1 mice and a 100-fold increase in LD₅₀ for He-J mice.
-If researchers repeated the analyses using F2 generation mice, spleen cell cultures exposed to SRC plus 1.0 μg Ph-LPS would be expected to have anti-SRC titers of:16001200800

Quizplus · Accepted Answer

11ecba2d_0f3f_64a0_a3bf_3dc9a961e926_MD0008_00 The experiment describes a monohybrid cross, or a mating between individuals with different alleles at one genetic locus. The first cross is performed between homozygous He-N [tlr4(+)/tlr4(+)] and He-J mice [tlr4(d)/tlr4(d)], members of the parental or P generation, and produces a heterozygous F1 generation [tlr4(+)/tlr4(d)]. The second cross would be performed between members of the F1 generation and would produce an F2 generation with a mix of genotypes. Depending on the genotype, some F2 offspring would be phenotypically similar to members of the P generation whereas some F2 offspring would resemble members of the F1 generation. For instance, expected F2 genotypes can be used to deduce anti-SRC titers when spleen cell cultures are exposed to SRC plus 1.0 μg Ph-LPS: tlr4(+)/tlr4(+): An estimated 25% of F2 mice would be homozygous for the normal functioning Tlr4 allele. These mice would have an immune response similar to that seen in He-N mice. According to Table 1, this corresponds to an antibody titer of 1605 ± 55 (Number I). tlr4(+)/tlr4(d): An estimated 50% of mice would be heterozygous for the Tlr4 gene mutation. These mice would have an immune response similar to F1 generation mice, or an antibody titer of 1240 ± 58 (Number II). tlr4(d)/tlr4(d): An estimated 25% of mice would be homozygous for the Tlr4 gene mutation. These mice would have an immune response similar to He-J mice, or an antibody titer of 810 ± 17 (Number III). Educational objective: In a monohybrid cross, members of the P generation are homozygous for different alleles at one locus. The first cross produces heterozygous offspring in the F1 generation. The second cross produces a mix of genotypes and phenotypes observed in members of the F2 generation.

Passage Lipopolysaccharides (LPS) Found in Gram-Negative Bacterial Cells Can Elicit a a Lethal