i, Fascinated by the immune responses to helminth pathogens (worms), you make an
ID: 212926 • Letter: I
Question
i, Fascinated by the immune responses to helminth pathogens (worms), you make an IL-5 knockout mouse (IL-5-/-) and infect them with worm larva (Schistosoma sp.). You notice that although the helminths are heavily coated with gE antibody, they are never cleared from your IL-5 knockout mice. Why are worms still able to be coated with JgE antibody in IL-5-/- mice? 1- 2 sentences. (2 points) ii. Describe the mechanism by which an JRE coated worm is normally killed, and why are they not killed in IL-5-/- mice? Be specific. 2 -4 sentences. (4 points) iii. The eggs shed by the helminth release toxins that destroy surrounding tissue. Describe the cellular immune response required to destroy eggs and neutralize these toxins. 2- 4 sentences. (4 points)Explanation / Answer
1- Large parasites, such as worms, cannot be ingested by phagocytes; however, when the worm is coated with antibody, especially IgE, eosinophils can attack it through their binding to the high-affinity FcRI. These cells will release toxic contents of their granules directly onto the target, a process known as exocytosis.
2- IL5-/- mice lost more weight during the infection than normal mice and took longer to regain their initial weight after expelling the worms. The number of eosinophils increased in the bone marrow, peritoneal cavity and small intestine of IL-5+/+ mice, but not IL-5-/- mice in primary infection. Not killed in IL5-/- because of No significant differences between infected IL-5+/+ and IL-5-/- mice in mast cells or other leucocytes were observed in the peritoneal cavity. Thus, IL-5 functions to protect the host in a primary infection. mice by limiting the number and fecundity of worms establishing in the small intestine. This protection is correlated with elevated blood and tissue eosinophilia which occurs in normal mice but not in IL-5-/- mice.
3- ADCC and type 1 hypersensitivity are involved to block their migration in gut mucosa and to eliminate the parasite. nitric oxide (NO), toxic to the worm, is released by the macrophages classically activated by IFNand TNF.
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