WBR0340
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Immunology |
| Sub Category | SubCategory::General Principles |
| Prompt | [[Prompt::To study the cellular responses to Influenza virus infection, a student exposes 2 groups of mice to the virus, one group with completely ablated bone marrows, and another control group with intact bone marrows. The student notices that in the control group, levels of an intracellular protein (Protein A) in muscle cells rise in parallel with the intracellular activity of 2′–5′ oligoadenylate synthetase and serum levels of IFN-α/β. This reaction is absent in the group with ablated bone marrows, whereas Influenza viral load is much more elevated than the control group. What is the most likely function of protein A?]] |
| Answer A | AnswerA::Phospholipase |
| Answer A Explanation | AnswerAExp::Interferons do not induce an antiviral response by activating phospholipases. |
| Answer B | AnswerB::Endonuclease |
| Answer B Explanation | AnswerBExp::Interferons do not induce an antiviral response by activating endonucleases. |
| Answer C | AnswerC::Protease |
| Answer C Explanation | AnswerCExp::Interferons do not induce an antiviral response by activating proteases. |
| Answer D | AnswerD::Deoxyribonuclease |
| Answer D Explanation | AnswerDExp::Interferons do not induce an antiviral response by activating deoxyribonuclease. |
| Answer E | AnswerE::Ribonuclease |
| Answer E Explanation | AnswerEExp::Interferons activate a ribonuclease (RNase L) that creates an antiviral state in neighboring cells by destroying viral RNA. |
| Right Answer | RightAnswer::E |
| Explanation | [[Explanation::Interferons represent a diverse family of proteins involved in cell growth, antiviral defense, and immune activation. Interferons are of 2 major types. Type I interferons are the product of a direct response to viral infection consisting of IFN-α produced mainly by the immune system, and IFN-β produced by most cell types. Type II interferons represent the IFN-γ product that is usually produced after the recognition of infected cells by T-lymphocytes. IFNs induce an antiviral state within target cells by activating RNAse L a ribonuclease that breaks down viral RNA and inhibits viral replication. RNAse L is activated by 2′–5′ oligoadenylate synthetases, a group of enzymes induced by interferon binding to its receptor.
Educational objective: Interferons create an antiviral state within the target cells by activating RNAse L a ribonuclease that breaks down viral RNA. Reference: |
| Approved | Approved::No |
| Keyword | WBRKeyword::Interferon, WBRKeyword::Ribonuclease, WBRKeyword::RNAse L |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |