When any pathogen invades the body, it has to pass several lines of defence. The first barrier is the skin and mucous membrane which is a physical and chemical barrier. The second line of defence is the non-specific response by macrophages, neutrophils and interferon. After crossing these two barriers the third line of defence comes into action in which, the B- cells and T-cells act specifically on the pathogen and destroy it.
When first and second line of defense is passed by the bacteria, the third line of defense will come into action which is a biological barrier which includes antigen which are anti-bodies generating substances.
The function of a vacuole is to store food or any other type of nutrients the cell might need to survive. This is true for both the plant and animal cell, though in the plant cell the vacuole's are much larger.
