around a bit keeps a variety of systems in good health, especially your cardiovascular system. Working out also directly boosts your immune system, because it promotes good circulations of fluids throughout your body. In a nutshell, just by moving, stretching, and squashing your various body parts, your fluids flow better and more freely than if you lie on your couch all day. And good circulation is good for the immune system because it allows your cells and immune proteins to move more efficiently and freely, which makes them do their job better.
