WBR0484

Author	[[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D.)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Immunology
Sub Category	SubCategory::General Principles
Prompt	[[Prompt::The innate immune system includes a variety of cell types that act as a primary response to infection. One major player in the innate immune system harbors a key protective component known as major basic protein and is induced to proliferate in the presence of IL-5. Which of the following cellular functions also correlates with the cell described above?]]
Answer A	AnswerA::Modulation of mast cell reaction
Answer A Explanation	[[AnswerAExp::Eosinophils limit the extent of the allergic reaction following mast cell degranulation by releasing histaminase and arylsulfatases.]]
Answer B	AnswerB::Mediation of allergic reactions
Answer B Explanation	AnswerBExp::Mast cells and basophils are the important players in mediating allergic reactions.
Answer C	AnswerC::Scavenging of damaged cells
Answer C Explanation	AnswerCExp::Although eosinophils have phagocytic properties for antigen-antibody comploxes, other phagocytes, such as macrophages and dendritic cells, scavenge dead cells and bacterial debris.
Answer D	AnswerD::Mediation of acute inflammatory responses
Answer D Explanation	AnswerDExp::The initial mediators of acute inflammatory responses are mainly neutrophils and macrophages.
Answer E	AnswerE::Production of antibodies
Answer E Explanation	AnswerEExp::Plasma cells are responsible for antibody production.
Right Answer	RightAnswer::A
Explanation	[[Explanation::Eosinophils have a multitude of basic functions that include non-specific cytotoxicity and host defense against helminthic parasitic infections. They contain mediators that are required to regulate both innate and adaptive immune responses. Eosinophils regulate immune regulation by expression of Th1 cytokines (IL-12 and IFN-gamma), Th2 cytokines (IL-4, IL-5, IL-9, IL-13, and IL-25), acute pro-inflammatory cytokines (TNF-alpha, IL-1 beta, IL-6, and IL-8), and inhibitor cytokines (TGF-beta and IL-10). They are partly responsible for tissue remodeling and repair by releasing growth factors, cytokines, chemokines, enzymes, lipid mediators, and reactive oxygen species. Also, eosinophils are important for parasite killing by release of reactive oxygen species and major basic protein, a toxic eosinophil effector mediator. They are also important for limiting mast cell degranulation by release of histaminase and arylsulfatases. Emerging animal studies have discovered novel roles of eosinophils in plasma cell survival, thymic development, maintanence of metabolic homeostasis, physiologic function of the female reproductive tract, mammary gland development, response to respiratory viral infection, pulmonary hypertension and acute lung injury, inflammatory bowel disease, cancers, among other physiological and pathological disorders. Educational Objective: Eosinophils have a multitude of basic functions that include: non-specific cytotoxicity and host defense against helminthic parasitic infections. Eosinophils limit the extent of the allergic reaction following mast cell degranulation by releasing histaminase and arylsulfatases. References: Rothenberg ME, Hogan SP. The eosinophil. Annu Rev Immunol. 2006;24(1):147-74. First Aid 2014 page]]
Approved	Approved::No
Keyword	WBRKeyword::Eosinophils, WBRKeyword::IL-5, WBRKeyword::Major basic protein
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::