Defense mechanisms: protecting the healthy lung

In addition to performing its primary function of gas exchange, the lung plays a critical role in defending the body against a hostile environment. The highly efficient nonspecific defense mechanisms help to preserve the lung structure and function. Specific immune mechanisms exist both systemically and locally. Activation of these latter responses may result in protection or in hypersensitivity. Failure of one or more components of the defense system of the lung may result in acute or chronic disease and may exacerbate or contribute to other concurrent illnesses.