Lung Defense
1. Particles removed from inspired air by the nose.
2. The larynx acts as sphincter during cough.
3. Protective agents in the lung lining fluids.
i. Surfactant
à bacterial opsonisation.
ii. Immunoglobulin
à IgA, IgM, IgG.
iii. Complement.
iv. bactericidal proteins and proteinase inhibitors that protect host tissue during the inflammatory response.
4. Alveolar macrophaes.

Source: Internal Medicine Book of Dr.Osama Mahmoud (Ain Shams University)