Passage Lipopolysaccharides (LPS) Found in Gram-Negative Bacterial Cells Can Elicit a a Lethal
Multiple Choice
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
![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 × 10<sup>5</sup> 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.<strong>Table 1</strong> 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. <strong>Figure 1</strong> Average serum interferon levels in mice cohortsExperiment 3Mice were injected with varying doses of Ph-LPS and monitored for 4 days. The lethal dose (LD<sub>50</sub>) 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 LD<sub>50</sub> for F1 mice and a 100-fold increase in LD<sub>50</sub> for He-J mice. -In an isolated population of 10,000 mice, 1,600 are homozygous for a Tlr4 defect. Assuming stable allele and genotype frequencies, how many mice are heterozygous for a Tlr4 defect? A) 2,400 B) 3,600 C) 4,800 D) 5,200](https://d2lvgg3v3hfg70.cloudfront.net/MD0008/11ecba2d_0f3e_2c1d_a3bf_85095183ef29_MD0008_00.jpg)
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.
![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 × 10<sup>5</sup> 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.<strong>Table 1</strong> 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. <strong>Figure 1</strong> Average serum interferon levels in mice cohortsExperiment 3Mice were injected with varying doses of Ph-LPS and monitored for 4 days. The lethal dose (LD<sub>50</sub>) 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 LD<sub>50</sub> for F1 mice and a 100-fold increase in LD<sub>50</sub> for He-J mice. -In an isolated population of 10,000 mice, 1,600 are homozygous for a Tlr4 defect. Assuming stable allele and genotype frequencies, how many mice are heterozygous for a Tlr4 defect? A) 2,400 B) 3,600 C) 4,800 D) 5,200](https://d2lvgg3v3hfg70.cloudfront.net/MD0008/11ecba2d_0f3e_532e_a3bf_2bc230da9462_MD0008_00.jpg)
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.
-In an isolated population of 10,000 mice, 1,600 are homozygous for a Tlr4 defect. Assuming stable allele and genotype frequencies, how many mice are heterozygous for a Tlr4 defect?
A) 2,400
B) 3,600
C) 4,800
D) 5,200
Correct Answer:
Verified
Correct Answer:
Verified
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