When exposure to a pathogen identical to one that has been encountered previously occurs again, the immune system recognizes the pathogen and acts quickly based upon:

PAMPs (Pathogen Associated Molecular Patterns)

Explanation:

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.