Kell factor

The Kell factor is like a secret code that our red blood cells can have or not have. It's called Kell because it was discovered by a scientist named Kell.

When we get a blood transfusion, it's important to match the Kell factor in the donor blood with the Kell factor in our own blood. If the Kell factors don't match, our immune system might recognize the transfused blood as a foreign invader and attack it, which can be very dangerous.

It's kind of like if you were in a secret club and had a secret handshake. If someone came along and tried to join the club but didn't know the secret handshake, you might be suspicious of them and not let them in. Similarly, our immune system can be suspicious of blood with a different Kell factor and not accept it as "belonging" in our body.

So, doctors always check the Kell factor before giving a blood transfusion to make sure it's a match. That way, they can keep us safe and healthy!