Written by Gidi Shemer, University of North Carolina at Chapel Hill
When discussing the immune system in human physiology, the military is the star of the show. The first line defense (e.g. our skin) can be represented by the physical barriers we have in our borders, defending us from the enemy (e.g. bacteria). The second line of defense (e.g. the phagocytes of the innate immune system) is represented by the soldiers who are found at the front lines. The third defense, the adaptive immune system, our B and T cells, is represented by the elite forces. These elite forces are more expensive, hard to come by, and called to action by the plain soldiers, but they provide modern, selective, and sophisticated tactics to fight the enemy.