WBR0736
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Immunology |
| Sub Category | SubCategory::Hematology |
| Prompt | [[Prompt::Neutrophils are considered a primary line of defense against bacterial infections and non-specific inflammatory processes. They are an important component of the innate immune response and are able to migrate by a process called chemotaxis. Chemotaxis requires complex intracellular signaling pathways that allow neutrophils to move towards chemoattractant molecules that drive them towards regions of inflammation. According to the image below, which of the following pathways is most likely involved in neutrophil chemotaxis? |
| Answer A | AnswerA::A |
| Answer A Explanation | AnswerAExp::LTB4 plays a major role in neutrophil chemotaxis. |
| Answer B | AnswerB::B |
| Answer B Explanation | AnswerBExp::LTC4 and LTD4 are important to increase bronchial tone and play a role in inflammatory bronchoconstrictive lung diseases, such as asthma. |
| Answer C | AnswerC::C |
| Answer C Explanation | AnswerCExp::The classical role of prostacyclin (PGI2) is the prevention of platelet aggregation. It also decreases vascular, bronchial, and uterine tonicity. |
| Answer D | AnswerD::D |
| Answer D Explanation | [[AnswerDExp::Prostaglandins share some characteristics with prostacyclin; they decrease vascular and bronchial tone. However, they have an opposing role in the uterine tonicity. They increase uterine tone; as such prostaglandin analogs may be used in conjunction with other medications to induce labor in pregnancy.]] |
| Answer E | AnswerE::E |
| Answer E Explanation | AnswerEExp::Thromboxane (TXA2) has an opposing role to prostacyclin at the levels of the platelets. It increases platelet aggregation. Also, it increases vascular and bronchial tone. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::Chemotaxis is an important feature of neutrophils, which allows it to migrate into specific sites of inflammation and to defend against bacterial infection. The pathway shown in the image is the arachidonic acid pathway that involves 2 main enzymes: Lipoxygenase which forms hydroperoxides to yield leukotrienes, and cycloxygenase (COX), which forms endoperoxides. The 2 enzymes have significant roles in different unrelated domains. In the pathway, LTB4 is an important neutrophil chemotactic agent.
Educational Objective: LTB4 is an important neutrophil chemotactic agent. Reference:
Nuzzi PA, Lokuta MA, Huttenlocher A. Analysis of neutrophil chemotaxis. Methods Mol Biol. 2007; 370:23-36 |
| Approved | Approved::No |
| Keyword | WBRKeyword::neutrophil, WBRKeyword::chemotaxis, WBRKeyword::LTB4, WBRKeyword::leukotriene, WBRKeyword::arachidonic acid, WBRKeyword::lipoxygenase, WBRKeyword::inflammation, WBRKeyword::chemoattractant |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |
