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PS3_key - Bi114 Problem Set 3. ANSWER KEY: 50 points total...

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Bi114 Problem Set 3. ANSWER KEY: 50 points total 1. Atarashi et al. 2011. Science 30 points total (5 points) a. In the introduction, the authors point out that there are numerous species of commensal bacteria that interact with the host immune system . How did they narrow their search to Clostridium species? 2.5pts: Figure 1D: authors treated SPF mice with antibiotics that target Gram-positive (vancomycin) or Gram-negative (polymyxin B) bacteria 2.5pts: Figure 1E: authors orally inoculated GF mice with 3% chloroform- resistant fecal microorganisms (spore-forming microorganisms) (5 Points) b. How do we know that the lower [%] Foxp3 + in CD4 in lymphocyte populations from GF mice (as compared to those from SPF mice) seen in Figure 1B is likely due to an absence of microbial-induced signaling events in these 8 week old mice but not due to some aberrant phenotype that emerged earlier in life? Figure 1C: authors colonized GF mice with fecal suspensions from SPF mice (“conventionalization”), and observed an increase in the frequency of Tregs in colonic LP (5 points) c. The authors claim that Clostridia induce IL-10-expressing T regs in the colon. How does the data presented in Figure 3 support this claim and not simply a correlation between the presence of Clostridium species and IL-10 expression?
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PS3_key - Bi114 Problem Set 3. ANSWER KEY: 50 points total...

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