WBR0680

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Serge Korjian)]]
Exam Type	USMLE Step 1
Main Category	Immunology
Sub Category	Infectious Disease
Prompt	A 24-year-old man, with no significant past medical history, presents to the emergency department (ED) with complaints of abdominal pain and bloody diarrhea of several days duration. The patient is found to have amoebic cysts on stool analysis. Which of the following cytokines is most likely elevated in this patient?
Answer A	IL-8
Answer A Explanation	IL-8 is a chemotactic factor for neutrophils.
Answer B	IL-2
Answer B Explanation	IL-2 stimulates growth of helper, cytotoxic, and regulatory T cells.
Answer C	IL-4
Answer C Explanation	IL-4 induces differentiation into Th2 cells and growth of B cells. It also enhances class switching into IgE
Answer D	IL-5
Answer D Explanation	IL-5 is activated to promote differentiation of B cells. It allows class switching into IgA and allows growth and differentiation of eosinophils.
Answer E	IL-10
Answer E Explanation	IL-10 is secreted by Treg cells and is activated in inhibit inflammation.
Right Answer	D
Explanation	Amoebic cysts in a patient with bloody diarrhea and abdominal pain is diagnostic of amoebic dysentery. Amebic dysentery is most common among travelers to developing countries and may be confused with traveler's diarrhea (although it is usually more severe). Intestinal amoebiasis is a parasitic infection, and eosinophilia is one of the classical signs observed among infected patients. Eosinophils play a major role in controlling parasitic infections by producing major basic protein and peroxidase. Eosinophils are induced to grow and to differentiate by specific cytokines, namely interleukin (IL)-5. Other cytokines play different pro-inflammatory roles, such as IL-8 in neutrophil chemotaxis and IL-4 in differentiation into Th2 cells, whereas others have anti-inflammatory roles, such as IL-10 and TGF-beta that are secreted by Treg cells. Educational Objective: IL-5 is activated in parasitic infections to enhance growth and differentiation of eosinophils. References: Takatsu K, Nakajima H. IL-5 and eosinophilia. Curr Opin Immunol. 2008;20(3):288-94. First Aid 2015 page 207
Approved	Yes
Keyword	Eosinophil, Eosinophilia, Eosinophils, Major basic protein, Peroxidase, Amoebiasis, Amebiasis, Entamoeba histolytica, Gastroenteritis, Parasitic, Interleukin, Interleukin 5, IL-5, IL5
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