Major histocompatibility complex

Imagine your body is like a house and the doors are the entrances to your cells. The major histocompatibility complex (MHC) is like the security guard standing at the door, checking everyone who enters. The MHC helps your body identify and recognize its own cells from the cells of other things that might harm it, like germs or viruses.

The MHC is like a big complicated puzzle that has to match one piece with another. Your body has millions of different pieces that make up the MHC puzzle, and each person's puzzle is unique. Even people who are related have different MHC puzzles.

When your immune system comes across a foreign object like a virus, it takes a little piece of it and shows it to the MHC puzzle at the door. If the MHC recognizes the piece, it lets the immune system know that it's okay to attack and destroy the foreign object. If the MHC doesn't recognize the piece, it tells the immune system to leave it alone.

Sometimes, the MHC doesn't work properly and can't recognize a foreign object as harmful. In these cases, the immune system can mistakenly attack your own cells instead, which can lead to diseases like autoimmune disorders.

So, the MHC is like the bouncer at the door of your cells, making sure only the right things get in.