Nib asked
How does the immune system fight viruses?
Your body fights a virus in two waves: fast, general defenders first, then a trained team of T cells and antibodies that also leaves memory cells behind for next time.
8 steps, drawn by Nib. Read it here, or watch him draw it. Updated .
1the invader
A virus can't do anything alone. It docks on one of your cells and slips inside, because it needs the cell's machinery to copy itself.
2a virus factory
Inside, the virus turns the cell into a copy factory. Within hours one virus becomes hundreds, which burst out and infect neighboring cells.
3the alarm
An infected cell can't save itself, but it can warn others. It releases a chemical alarm called interferon, and neighbors that receive it harden their defenses.
a common mix-upMuch of how sick you feel, such as fever and aches, is your immune response at work, not damage from the virus alone.
4the cleanup crew
Meanwhile macrophages, big cleanup cells, swallow free viruses. The alarm also raises your temperature. Fever slows the virus and speeds your defenders.
5the team
The macrophage also shows a scrap of the virus to a helper T cell, the team captain. Helper T cells wake up B cells and killer T cells. The first time, that takes a week or two.
6antibodies
B cells make antibodies, Y-shaped proteins that lock onto free virus. That blocks the virus from docking and tags it for the macrophages to eat.
a common mix-upAntibodies do not destroy viruses themselves: they block them from entering cells and tag them for destruction by other immune cells.
7killer T cells
But antibodies can't reach a virus hiding inside a cell. That job belongs to killer T cells, which find infected cells and destroy them before the new copies burst out.
8the whole idea
So, the whole idea: fast general defenders first, then antibodies and killer T cells aimed exactly at this virus. And memory cells stay, so the next meeting is fast.
Your body wins in two waves: quick general defenders, then a trained team that remembers the virus for next time.