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

Interferons (IFNs) are crucial cytokines that provide antiviral defense by alerting neighboring cells of viral infections. Infected cells release IFNs, prompting nearby cells to produce inactive antiviral proteins (IAVPs). If these neighboring cells encounter the virus, IAVPs activate into active antiviral proteins (AVPs), which inhibit viral replication and trigger apoptosis, effectively sacrificing the cell to prevent further infection. This interferon response is vital for limiting viral spread and buying time for the immune system to eliminate the virus.

Interferons

This video, we're going to begin our introduction to the interferon response. And so first, we need to recall from some of our previous lesson videos that interferons are commonly abbreviated as IFNs. And these interferons are one of many different types of cytokines or chemical signals used to communicate between cells. And so these interferons are specifically cytokines that provide antiviral effects, or in other words, it helps to provide defense against viruses. And it will provide these antiviral effects to neighboring cells. And so we'll be able to talk more details about the steps of the interferon response in our very next lesson video. But 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. And 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. And so once again, in our next lesson video, we'll get to talk a lot more details about this interferon response in order to understand how it allows for antiviral effects. And so I'll see you all in our next video.

Steps of the Interferon Response

In this video, we're going to talk more details 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, down 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 go on to diffuse to a neighboring cell and bind to that neighboring cell in order 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 I can save my neighbors if I release interferons. And so the first cell, although it knows it is going to die by the virus, it 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, they 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 I AVPs, 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, it detects the interferons, and the detection of the interferons allows the neighboring cell to produce those I AVPs, 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, that can actually activate that neighboring cell's inactive Antiviral Proteins. And the activation of inactive Antiviral Proteins will form AVPs, active viral, active antiviral proteins. And these active antiviral proteins or AVPs, they 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 the 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, it releases those interferons so that the neighboring cell can respond to those interferons. However, the first cell, again, the infected cell is going to ultimately die. It will produce new viruses, so more viruses will be, produced. And, again, the infected cell here is going to lyse. So it is going to die. However, by releasing the interferons, the first infected cell is making an effort to help control the replication of the virus by, allowing for antiviral proteins to be produced. And so notice that later down the line if this virus ever tries to make an attempt to infect this neighboring cell, this neighboring cell has these inactive antiviral proteins. And the neighboring cell, if it is ever infected by the virus, the inactive antiviral proteins, the I AVPs, are able to activate into AVPs. And so notice that the bubble speech here in the neighboring cell is saying, hey, sorry virus, I know you're trying to infect me, but you're not going to us

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 enveloped viruses.
• B. It decreases the spread of the virus.
• 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 the immune response?

Interferons (IFNs) are a type of cytokine, which are chemical signals used for communication between cells. They play a crucial role in the immune response by providing antiviral defense. When a cell is infected by a virus, it releases interferons. These interferons then diffuse to neighboring cells, warning them of the viral presence. In response, these neighboring cells produce inactive antiviral proteins (IAVPs). If the virus attempts to infect these cells, the IAVPs activate into active antiviral proteins (AVPs), which inhibit viral replication and trigger apoptosis, effectively sacrificing the cell to prevent further infection. This process helps limit the spread of the virus and buys time for the immune system to eliminate it.

How do interferons alert neighboring cells of a viral infection?

When a cell is infected by a virus, it can produce and secrete interferons (IFNs). These interferons diffuse to neighboring cells that have not yet been infected. Upon reaching these neighboring cells, the interferons bind to specific receptors on their surfaces. This binding acts as a warning signal, prompting the neighboring cells to produce inactive antiviral proteins (IAVPs). These IAVPs remain inactive until the neighboring cell detects viral RNA, at which point they activate into active antiviral proteins (AVPs) that inhibit viral replication and trigger apoptosis. This mechanism helps protect neighboring cells from becoming viral hosts.

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

Inactive antiviral proteins (IAVPs) are proteins produced by neighboring cells in response to interferons (IFNs) released by an infected cell. These proteins are initially inactive and do not perform any antiviral functions. However, if the neighboring cell becomes infected by the virus, the detection of viral RNA triggers the activation of IAVPs into active antiviral proteins (AVPs). The AVPs then inhibit viral replication by degrading the cell's mRNA and stopping translation, ultimately leading to apoptosis. This process sacrifices the infected cell to prevent the virus from using it 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. When a neighboring cell, warned by interferons, detects viral RNA, it activates its inactive antiviral proteins (IAVPs) into active antiviral proteins (AVPs). These AVPs inhibit viral replication by degrading the cell's mRNA and stopping translation. This process triggers apoptosis, effectively sacrificing the infected cell. By undergoing apoptosis, the cell prevents the virus from using it as a host to replicate, thereby limiting the spread of the virus. This mechanism helps control the infection and buys time for the immune system to eliminate the virus.

How does the interferon response help limit viral replication?

The interferon response helps limit viral replication by warning neighboring cells of a viral infection. When an infected cell releases interferons (IFNs), these cytokines diffuse to nearby cells and bind to their receptors. This binding prompts the neighboring cells to produce inactive antiviral proteins (IAVPs). If these cells later encounter the virus, the IAVPs activate into active antiviral proteins (AVPs), which inhibit viral replication by degrading the cell's mRNA and stopping translation. This process triggers apoptosis, sacrificing the infected cell to prevent the virus from using it to replicate. By limiting viral replication, the interferon response helps control the spread of the virus and buys time for the immune system to eliminate it.