I've heard in many documents said that :
There are 25 million to a billion different T-cells in your body. Each cell has a unique T-cell receptor that can fit with only one kind of antigen - quoted from askabiologist.
But I haven't found the mechanism of this. How our body produce too many different T-cells? Does our genome need to have 25 million to billion genes to encode for 25 million to billion unique receptor for those T-cells? Does each T-cell have a different gene region on their genome or they have a different turned-on/turned-off genes ?