Vastustuskykymme tekee töitä kellon ympäri ilman, että sitä erityisemmin huomaamme.

This text explains how the immune system protects the body continuously against infections and invading pathogens. It describes the body's external defenses such as skin, tears, saliva, mucous membranes, lungs, stomach acid, gut immune cells, and the liver. The piece is educational and focused on basic immune defense functions.