We know that our body has an amazing defense mechanism, called our immune system, against these types of infections that are triggered by every foreign agent that enters our bodies. Our immunity scans, catalogs, fights, and remembers harmful entities that can wreak havoc. But the beauty of this highly intricate immune system is that it is also highly efficient, using a sequence of protein signals to either signal other proteins that then lead to signalling the cells needed to fight the infections, or to signal those cells directly. It is a cascading system. And many of these protein signals, called cytokines, can do more than just trigger another protein or cell; it can also shut it down.
Interferon is a cytokine that is one such major player. There are many types, so they are classified by what cell releases them and what other signal, or cell, it triggers in turn. Type I interferons can be secreted by any of our cells, and so is handy as a first-line defense when a cell is initially infected by a virus. When a virus enters a cell it releases Type I interferons which alert other cells or signal other proteins to help it attack other invading virus particles.
However, as a self-regulated process (much like your hungry brain triggering you to reach for a candy bar, and then the conscious part of your brain making you put the rest of the 6-pack down...in theory), these Type I interferons may also suppress the very same cells they are signalling, in order to ensure that the immune response doesn’t run away like a freight train.
The problem with that is, if the virus happens to be replicating very quickly, it can overrun our cells. Looking at the blue arrow in the image, the persisting presence of virus continues to the trigger our immune system.
Now, what do you think will happen in this situation? Answer, next post!