Innate immunity of the lungs in homeostasis and disease

Humans breathe thousands of litres of non-sterile air each day containing bacteria, viruses, and fungi, as well as pollutants, allergens, and other particles. The continual exposure to foreign particles is juxtaposed with the vast surface area of the blood-air-barrier which becomes extremely thin to allow for efficient gas exchange. To prevent infection and injury, the healthy lung relies on a robust innate immune system to protect itself. Critically, this innate immune system must clear insults while maintaining immune tolerance and minimizing inflammation to avoid disrupting the lung's vital gas exchange function. In this review, we discuss how the innate immune system protects the lung from its environment.