WBR0340
| 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::In order to study the cellular response, a student exposes two groups of mice to an influenza virus infection, one group with completely ablated bone marrow, and a control group with intact bone marrow. The student observes 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 parallel reaction is absent in the group with ablated bone marrow, whereas influenza viral load is much more elevated than the control group. Which of the following is the most likely the 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::See explanation. |
| Right Answer | RightAnswer::E |
| Explanation | [[Explanation::Interferons are a diverse family of proteins involved in cell growth, antiviral defense, and immune activation. Type I interferons, products of a direct response to viral infection, consist of IFN-α produced mainly by the immune system, and IFN-β produced by most cell types. Type II interferons, IFN-γ products, are 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, which breaks down viral RNA and inhibits viral replication. RNAse L is activated by 2'-5′ oligoadenylate synthetases, a group of enzymes induced by an interferon binding to its receptor. Educational Objective: Interferons induce an antiviral state within the target cells by activating RNAse L, a ribonuclease, which breaks down viral RNA. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Interferon, WBRKeyword::Ribonuclease, WBRKeyword::RNAse L, WBRKeyword::enzyme, WBRKeyword::enzymes, WBRKeyword::induce |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |