How does a capsule help certain bacteria evade detection by the immune system? How does a capsule help certain bacteria evade detection by the immune system? The capsule is composed of polysaccharides that are similar to those found in the host; thus, the immune system does not recognize it as foreign. The capsule makes the bacterium too sticky to be phagocytosed by the immune cells. Capsules have the ability to destroy antibodies secreted by the immune system. Capsules allow the bacteria to stick together, creating a larger mass that is too big for immune cells to engulf.