The Spleen
This is a body organ situated at the left side of our stomach, and mainly controls the quality of our blood. As mentioned above, the white blood cells are responsible for destroying various types of harmful infections. Our spleen is palace where certain types of white blood are produced. These blood cells create a substance called antibodies, which can kill harmful infection, bacteria etc. Also, when we have worn out and damaged red blood cells and platelets in our blood, they too are destroyed in the spleen, by the white blood cells. Apart from this, the spleen stores a large amount of blood.
This stored blood is sent throughout the body through the blood stream when extra blood is needed due to an injury, emergency etc.
So, if our spleen becomes weak, we may have less white blood than normal amount of damaged and worn out red blood cells and platelets and less storage of extra blood etc. This means we are too open to illness.