Dendritic cells: How does the immune system know when there is an infection?

The immune system needs to find out if there's a microbe such as a virus that's replicating and causing an infection, plus the immune system wants to collect information about the virus in order to target it with custom-made weapons.

I use multiple analogies to explain what dendritic cells do in 4 chapters:

Chapter 1 Surveillance. Dendritic cells are like radar workers, constantly looking for enemy activity.

Chapter 2 Friend or foe. Dendritic cells have the responsibility of deciding if there is a microbial infection or not, a mistake here can be very costly.

Chapter 3 A journey to the lymph node. how do dendritic cells find their way to the lymph node to deliver enemy intel? And why weren't they moving in that direction before detecting an infection?

Chapter 4 A meeting of the immune cells. Dendritic cells meet other immune cells and take the war to the next phase. An army of clones will be created.

Disclaimer: I am a physician scientist at the University of Washington. However, this is a personal podcast, produced in my own time and is unaffiliated with the University of Washington.