Okay kiddo, so imagine that your body is like a castle with lots of walls and gates to protect it from bad germs and viruses. But sometimes, these bad guys are tricky and they try to sneak in. That's where mannan-binding lectin comes in.
Mannan-binding lectin, or MBL for short, is kind of like a knight in your body castle. It's a protein that travels around in your blood and looks out for any bad guys that might be trying to get in.
When MBL sees a bad guy, it attaches to it like a magnet and tells other cells in your body that there's an intruder. Those cells can then come and attack the bad guy before it can cause any harm.
MBL is especially good at finding certain kinds of bad guys, like bacteria and viruses that have something called mannose on their outer layer. That's why it's called mannan-binding lectin - it likes to bind to things with mannose on them.
So there you have it, MBL is like a knight that helps protect your body castle from bad guys with mannose. Pretty cool, huh?