WBR0141

Author	[[PageAuthor::Rim Halaby, M.D. [1] (Reviewed by Alison Leibowitz)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Immunology
Sub Category	SubCategory::General Principles
Prompt	[[Prompt::Neutrophils are critically involved in the process of inflammation. The sequence of events in the recruitment of neutrophils from the vessel lumen to the extracellular matrix, referred to as extravasation, and can be divided up into four steps. Which of the following signaling mediators is involved in the migration of the neutrophils across the endothelial cells?]]
Answer A	AnswerA::E selectin and P selectin
Answer A Explanation	[[AnswerAExp::E selectin and P selectin are involved in the rolling phase of extravasation.]]
Answer B	AnswerB::ICAM 1
Answer B Explanation	[[AnswerBExp::ICAM-1 is involved in the tight binding of neutrophils to the endothelium.]]
Answer C	AnswerC::PECAM 1
Answer C Explanation	[[AnswerCExp::PECAM-1 is involved in diapedesis, which is the migration of the neutrophils across the endothelial cells.]]
Answer D	AnswerD::C5a
Answer D Explanation	[[AnswerDExp::C5 a is involved in the migration of leykocytes through the interstitum towards the site of inflammation.]]
Answer E	AnswerE::Interleukin 8
Answer E Explanation	[[AnswerEExp::Interleukin 8 is involved in the migration of leukocytes through the interstitium towards the site of inflammation.]]
Right Answer	RightAnswer::C
Explanation	[[Explanation::PECAM-1 is involved in diapedesis, which is the migration of the neutrophils across the endothelial cells. The four steps of extravasation are: Margination and rolling Tight-binding Diapedsis is the migration of the neutrophils across the endothelial cells. Migration is the movement of neutrophils through the interstitium to the location of the infection, guided by C5a, IL-8, kallikrein, and platelet-activation factors, the signalling mediators. Educational Objective: Inflammation involves several steps including the rolling phase of the neutrophils, their binding to the endothelium, diapedesis, and migration to the site of inflammation. PECAM 1 is involved in diapedesis, which is the migration of the leukocytes across the endothelial cells. References: First Aid 2014 page 224]]
Approved	Approved::Yes
Keyword	WBRKeyword::Inflammation, WBRKeyword::Diapedesis, WBRKeyword::Leukocyte, WBRKeyword::Leukocyte adhesion, WBRKeyword::Endothelium, WBRKeyword::Endothelial cell
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