How does your body protect itself from antigens?

Answer 1

I don't know exactly how detailed you want me to go with this, but a simple answer is that it produces antibodies against those antigens. I guess an easy way to put it is that our white blood cells have the ability to fight off foreign materials (antigens), which is what our fighter T cells do. After we are exposed to those antigens, our body also makes "memory" cells (B cells), so that if we are exposed to the same antigen later in life, our body will "remember" how it fought them off the first time and respond quickly to remove them.

Answer 2

Cells use an antigen to recognise a pathogen. The cells then remove the pathogen.

If you would like to learn much more detail I suggest checking out the relevant visual aided videos from khan academy on YouTube. Look for the Biology class playlst