Respiratory immunity is accomplished using multiple mechanisms of the respiratory tract, mucosal defense in the form of the mucociliary apparatus, innate immunity using cells and molecules and acquired immunity. Immune-mediated lung diseases are a complex group of diseases characterized by inflammatory cellular infiltration of the lungs, which can result in progressive airway remodeling and parenchymal injury. Diseases have variable presentation depending on antigen exposure, patient predisposition, and type of immune response, as noted in the current book.