The system reacts to the foreign proteins of the invading pathogen by mobilising the white cells of the blood (macrophages) to engulf and destroy the invader.
(The system; reacts; to the foreign proteins of the invading pathogen) (the white cells of the blood; to destroy; the invader)
The system the white cells of the blood
reacts to destroy
to the foreign proteins of the invading pathogen
the invader