FIGURE 1.

Plasma exudation in uninjured airways: In response to viral/bacterial infection, allergic inflammation and topical challenges with autacoids, plasma macromolecules move to the surface of the pseudostratified epithelial barrier of human nasal and tracheobronchial airways. As reflected by a well‐maintained ratio between small (albumin) and large (alpha2‐macroglobulin) plasma proteins during their brief journey from the intravascular compartment to the surface of an intact mucosa, the exudation of bulk plasma is defined as a largely a non‐sieved process. Hence, as illustrated and discussed in this review, practically all circulating plasma molecules could be expected to be components of the airways surface exudate. This opportunity for a first‐line airways defence is precisely localized to mucosal sites affected by exposure to environmental challenges. Yellow colour = plasma proteins‐peptides. Modified from references 12, 13 and 51