Interferon question

[igcgnerd]

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Came across this in Uworld.

Female dx'd/ treated for influenza A. Interferons produced result in which of the following cellular changes?

a) decreased apoptosis of infected cells
b) decreased protein synthesis by infected cells
c) increased expression of MHC class 2
d) increased intracellular killing by macrophages
e) viral mRNA degradation and sparing of host mRNA.

Their answer was b. The reason I take issue with this is because even in their own explanation they said that interferon induces signaling in NEIGHBORING cells to synthesize anti viral proteins. That's why I didn't select it because it is infected cells making IFN and acting as a paracrine messenger on neighboring cells. I selected C because it seemed like the best choice. Any thoughts?

*correction I selected c. The correct answer per Uworld was B.

 

[thehundredthone]

I'm confused. The correct answer was B, which you didn't select. But you selected B?

Either way, the neighbouring cells do not become immune to viral infection, they just stop functioning as the virus's minions. The inhibition of protein synthesis means that the neighbouring cells, once infected, are useless to the virus as it cannot reproduce within them.

 

[igcgnerd]

I actually selected c. Sorry typo. The reason why I didn't select their answer was the IFN acts as a paracrine molecule, not autocrine. If it were infected cells acting on themselves to produce anti viral mRNA proteins, it would be an autocrine action. The specified infected cells creating IFN that then act on infected cells.

 

[jazzyazza]

I actually selected c. Sorry typo. The reason why I didn't select their answer was the IFN acts as a paracrine molecule, not autocrine. If it were infected cells acting on themselves to produce anti viral mRNA proteins, it would be an autocrine action. The specified infected cells creating IFN that then act on infected cells.

Hey. You are on the right track but slightly over-thinking it. IFN alpha and beta released by viral infected cells acts on neighbouring viral infected cells (paracrine signalling) to increase the synthesis of certain proteins that either degrade mRNA or inhibit translation. So ultimately the increased paracrine signalling leads to decreased protein synthesis in the viral cell, infected host cell, or both.

I think how you are looking at it is that if the viral infected cell is killed, the signalling involved is autocrine and not paracrine. Think of it this way...host cell X is infected and consequently stimulates the infected cells around it to undergo apoptosis (via paracrine signaling). Now, its neighbour infected host cell Y also induces paracrine signalling of the cells around it which includes cell X, thus leading to apoptosis of X. So X might not have killed itself, but its neighbour did. Hope I didnt lose you there.

 

[thehundredthone]

I actually selected c. Sorry typo. The reason why I didn't select their answer was the IFN acts as a paracrine molecule, not autocrine. If it were infected cells acting on themselves to produce anti viral mRNA proteins, it would be an autocrine action. The specified infected cells creating IFN that then act on infected cells.

The point that jazzyazza and I are trying to make is that the neighbouring cells can also be infected, and so the decreased protein synthesis does in fact take place in (neighbouring) infected cells.

As far as increased MHC-II is concerned, that's a function of Type II interferons (e.g. IFN gamma).