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{{WBRQuestion
{{WBRQuestion
|QuestionAuthor={{Rim}}
|QuestionAuthor={{Rim}} {{Alison}}
|ExamType=USMLE Step 1
|ExamType=USMLE Step 1
|MainCategory=Immunology
|MainCategory=Immunology
Line 20: Line 20:
|MainCategory=Immunology
|MainCategory=Immunology
|SubCategory=General Principles
|SubCategory=General Principles
|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?
|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?
|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.
|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 create an antiviral state within the target cells by activating RNAse L a ribonuclease that breaks down viral RNA.
|EducationalObjectives= Interferons induce an antiviral state within the target cells by activating RNAse L, a ribonuclease, which breaks down viral RNA.
|References= Goodbourn S, Didcock L, Randall RE. Interferons: cell signalling, immune modulation, antiviral response and virus countermeasures. J Gen Virol. 2000;81(Pt 10):2341-64.


Reference:<br>
Goodbourn S, Didcock L, Randall RE. Interferons: cell signalling, immune modulation, antiviral response and virus countermeasures. J Gen Virol. 2000;81(Pt 10):2341-64.
|AnswerA=Phospholipase
|AnswerA=Phospholipase
|AnswerAExp=Interferons do not induce an antiviral response by activating phospholipases.
|AnswerAExp= Interferons do not induce an antiviral response by activating phospholipases.
|AnswerB=Endonuclease
|AnswerB=Endonuclease
|AnswerBExp=Interferons do not induce an antiviral response by activating endonucleases.
|AnswerBExp= Interferons do not induce an antiviral response by activating endonucleases.
|AnswerC=Protease
|AnswerC=Protease
|AnswerCExp=Interferons do not induce an antiviral response by activating proteases.
|AnswerCExp= Interferons do not induce an antiviral response by activating proteases.
|AnswerD=Deoxyribonuclease
|AnswerD=Deoxyribonuclease
|AnswerDExp=Interferons do not induce an antiviral response by activating deoxyribonuclease.
|AnswerDExp= Interferons do not induce an antiviral response by activating deoxyribonuclease.
|AnswerE=Ribonuclease
|AnswerE=Ribonuclease
|AnswerEExp=Interferons activate a ribonuclease (RNase L) that creates an antiviral state in neighboring cells by destroying viral RNA.
|AnswerEExp= See explination.
|RightAnswer=E
|RightAnswer=E
|WBRKeyword=Interferon, Ribonuclease, RNAse L
|WBRKeyword=Interferon, Ribonuclease, RNAse L, enzyme, enzymes, induce,
|Approved=No
|Approved=Yes
}}
}}

Revision as of 13:47, 15 July 2014
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 explination.
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.
References: Goodbourn S, Didcock L, Randall RE. Interferons: cell signalling, immune modulation, antiviral response and virus countermeasures. J Gen Virol. 2000;81(Pt 10):2341-64.]]

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::
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