Interferon Response: Study with Video Lessons, Practice Problems & Examples

Interferons (IFNs) are crucial cytokines that provide antiviral defense by warning neighboring cells of viral infections. When pattern recognition receptors (PRRs) detect viral RNA in an infected cell, it secretes interferons, which diffuse to uninfected cells, prompting them to produce inactive antiviral proteins (IAVPs). If these neighboring cells encounter the virus, IAVPs activate into active antiviral proteins (AVPs), leading to apoptosis, which prevents viral replication. This interferon response is vital for limiting virus spread and buying time for the immune system to eliminate the infection.

Interferon Response

This video, we're going to begin our introduction to the interferon response. First, we need to recall from some of our previous lesson videos that interferons are commonly abbreviated as IFNs. These interferons are one of many different types of cytokines or chemical signals used to communicate between cells. Specifically, cytokines provide antiviral effects, or in other words, they help to provide defense against viruses and will offer these antiviral effects to neighboring cells. We'll be able to talk more about the steps of the interferon response in our very next lesson video. For now, if we take a look at our image down below, notice we're showing you our map of the lesson on innate immunity. Right now, here in this video, we're focusing specifically on the second line of defense on the innate effector actions, specifically the interferon response. Once again, in our next lesson video, we'll get to discuss a lot more details about this interferon response to understand how it allows for antiviral effects. I'll see you all in our next video.

Steps of the Interferon Response

In this video, we're going to talk more about the steps of the interferon response, which recall from our last lesson video, provides antiviral effects or defense against viruses in neighboring cells. Now before we begin, I want to first mention that the text that you see up above corresponds with the image that you see down below on the interferon response. And so one thing that we're going to do as we break this up is we're going to go from the text up above to the image down below so you can see how it corresponds.

And so here what we're saying is that when the PRRs or the pattern recognition receptors of an infected cell detect viral RNA, sometimes that infected cell can produce and secrete interferons, which recall interferons are commonly abbreviated as IFNs. And so, if we take a look at our image down below on the left-hand side over here, notice that we're showing you our first cell, and this first cell is being infected by a virus. And so notice that this is our virus, and notice that the virus here is infecting this cell that we have right here. And so, the virus is infecting the cell. However, this infected cell is sometimes able to create interferons. And so notice that this cell, although it is being infected, it is producing and secreting these interferon molecules. And the interferon molecules can again be produced by the first cell and diffuse over towards neighboring cells. And so again, what we're saying here is that the infected cell can produce and secrete interferons, and those interferons can diffuse to a neighboring cell and bind to that neighboring cell to warn that neighboring cell of the presence of the virus.

And so notice here, in the image, we have these little interferon molecules diffusing over to a neighboring cell here that has not yet been infected by the virus. Now notice this little bubble speech that's being said here by the first cell that is infected. Notice that because this cell here is being infected by the virus, it's saying, "I'm doomed." And so this first cell, although it is being infected by the virus and it is ultimately going to be killed by the virus, It's saying here that maybe it can save its neighbors if it releases interferons. And so the first cell, although it knows it is going to die by the virus, can release these interferons again to warn neighboring cells of the presence of the virus before the virus actually gets over to it. And so again here what we're saying is that these interferons that have been released by the first infected cell can diffuse over towards neighboring cells and bind to those neighboring cells that have not yet been infected.

And when the interferons bind to those neighboring cells that have not yet been infected, it can actually lead to the production of inactive antiviral proteins, or IAVPs, in those neighboring cells that have not yet been infected. And so if we take a look at our image down below, notice that these interferons that have diffused over to the neighboring cell over here allow for the production of IAVPs, inactive antiviral proteins. And so notice it says here that the neighboring cell receives the interferons, detects the interferons, and the detection of the interferons allows the neighboring cell to produce those IAVPs, Inactive Antiviral Proteins. Now these inactive antiviral proteins, as their name implies, they are inactive. And so because they are inactive, they are not going to do anything until they become activated. However, they are being expressed so they are ready to take action and become activated when the scenario presents itself.

And so notice that this bubble speech over here by the neighboring cell is saying, "Oh, I just got a message and the message is referring to the interferons that my neighbor was infected by a virus. So, I better make these antiviral proteins or IAVPs." Now if this neighboring cell down the line is ever infected by that virus, then the detection of that viral double-stranded RNA or just any type of viral RNA that is detected can actually activate that neighboring cell's inactive Antiviral Proteins. And the activation of inactive Antiviral Proteins will form AVPs, active antiviral proteins. And these active antiviral proteins, or AVPs, have the ability to stop translation of the cell by degrading the cell's mRNA. And ultimately, this will trigger apoptosis. And although apoptosis is programmed cell death that will kill the cell, it is also going to prevent the virus from using the cell as a host to replicate. And so ultimately, it will prevent virus replication. And so if we take a look at our image down below, notice that the first cell over here that is infected by the virus, again, releases those interferons so that the neighboring cel

How does the interferon response provide anti-viral protection?

• A. Interferons bind to the virus neutralizing it.
• B. Interferons stimulate neighboring cells to produce anti-viral proteins.
• C. Interferons prevent the virus from entering the cell.
• D. Interferons prevent the virus from leaving the infected cell and infecting neighboring cells.

If a cell produces antiviral proteins (AVPs) what occurs when that cell encounters dsRNA?

• A. The antiviral proteins trigger the production of iAVPs.
• B. The antiviral proteins cease protein translation in the cell so no viral proteins can be made.
• C. The antiviral proteins become activated and the cell undergoes apoptosis to stop the viral spread.
• D. The antiviral proteins trigger the production of interferon proteins to warn neighboring cells of viral infection.

How does the interferon response to an invading virus result in the infected cell undergoing apoptosis?

• A. Detection of viral RNA triggers the degradation of host RNA and stops translation which results in cell death.
• B. Detection of viral proteins inactivates the AVPs which triggers cells death.
• C. Detect of viral RNA ceases all functions of the cell and results in cell lysis and release of newly made viruses.
• D. Detection of viral proteins causes pores to form in the surface of the cell resulting in apoptosis.

Which of the following cells can induce viral-infected cells to undergo apoptosis?

• A. Neutrophils.
• B. NK cells.
• C. Eosinophils.
• D. B cells.
• E. Basophils.
• F. Red blood cells.

Which of the following statements about interferon is incorrect?

a) It only works on a few specific types of virus.

b) It makes cells resistant to viral infection.

c) It is a species-specific molecule.

d) It does not directly inactivate viruses.

• A. It only works on a few specific types of virus.
• B. It makes cells resistant to viral infection.
• C. It is a species-specific molecule.
• D. It does not directly inactivate viruses.

Here’s what students ask on this topic:

What are interferons and how do they function in antiviral defense?

Interferons (IFNs) are a type of cytokine, which are chemical signals used for communication between cells. They play a crucial role in antiviral defense by warning neighboring cells of viral infections. When pattern recognition receptors (PRRs) in an infected cell detect viral RNA, the cell secretes interferons. These interferons then diffuse to uninfected neighboring cells, prompting them to produce inactive antiviral proteins (IAVPs). If these neighboring cells later encounter the virus, the IAVPs activate into active antiviral proteins (AVPs), leading to apoptosis. This programmed cell death prevents the virus from using the cell to replicate, thereby limiting the spread of the virus and buying time for the immune system to eliminate the infection.

How do pattern recognition receptors (PRRs) contribute to the interferon response?

Pattern recognition receptors (PRRs) are crucial for initiating the interferon response. These receptors are located in cells and are responsible for detecting viral components, such as viral RNA. When PRRs in an infected cell recognize viral RNA, they trigger the production and secretion of interferons (IFNs). These interferons then diffuse to neighboring uninfected cells, warning them of the viral presence. This warning prompts the neighboring cells to produce inactive antiviral proteins (IAVPs), which can later be activated to combat the virus if the neighboring cells become infected. Thus, PRRs play a vital role in detecting viral infections and initiating the interferon response to limit viral spread.

What are inactive antiviral proteins (IAVPs) and how do they function?

Inactive antiviral proteins (IAVPs) are proteins produced by neighboring cells in response to interferons (IFNs) released from an infected cell. These proteins are initially inactive and do not perform any antiviral functions until they are needed. If a neighboring cell that has produced IAVPs becomes infected by a virus, the detection of viral RNA activates these IAVPs into active antiviral proteins (AVPs). The AVPs then inhibit viral replication by stopping the translation of the cell's mRNA and triggering apoptosis, or programmed cell death. This process prevents the virus from using the cell to replicate, thereby limiting the spread of the virus.

What role does apoptosis play in the interferon response?

Apoptosis, or programmed cell death, plays a critical role in the interferon response by preventing viral replication. When a neighboring cell that has produced inactive antiviral proteins (IAVPs) becomes infected by a virus, the detection of viral RNA activates these IAVPs into active antiviral proteins (AVPs). The AVPs then degrade the cell's mRNA, halting protein synthesis and triggering apoptosis. Although apoptosis results in the death of the infected cell, it also prevents the virus from using the cell as a host to replicate. This self-sacrifice mechanism helps to limit the spread of the virus and buys time for the immune system to eliminate the infection.

How do interferons help in limiting the spread of a virus?

Interferons (IFNs) help limit the spread of a virus by warning neighboring cells of an infection. When an infected cell detects viral RNA through its pattern recognition receptors (PRRs), it secretes interferons. These interferons diffuse to neighboring uninfected cells, prompting them to produce inactive antiviral proteins (IAVPs). If these neighboring cells later encounter the virus, the IAVPs activate into active antiviral proteins (AVPs), which halt viral replication by stopping protein synthesis and triggering apoptosis. This process prevents the virus from using the neighboring cells to replicate, thereby limiting its spread and buying time for the immune system to eliminate the infection.