Local Cell Flux and Cell Activation in Provoked and Naturally Occurring Allergic Rhinitis

Abstract

Several new techniques for atraumatic harvesting of cells from the nasal mucosa in vivo in humans have been utilized in allergen challenge experiments and during natural allergen exposure. Using biochemical techniques to monitor the release of substances or mediators, suggestive evidence has been provided for the participation of specific cells in these conditions. After a local challenge with allergen, a release of histamine indicates the activation of mast cells in the initiating part of the allergic response. This initial response to allergen is followed by a late inflammatory phase characterized by late occurring symptoms, a local influx of granulocytes, and a change in mucosal responsiveness to specific as well as unspecific stimuli. The interrelationship between these different manifestations of the postallergen inflammatory response remains to be sorted out. The most prominent finding is the increase in the number of eosinophilic granulocytes. Biochemical evidence has also been provided that these cells together with basophilic granulocytes also appearing during the late phase are activated. Similar evidence for the participation of mast cells in hay fever during natural allergen exposure has been provided through the demonstration of changes in the distribution of these cells, a change in intracellular histamine content and ultrastructural findings of cell activation. In addition, seasonal allergen exposure was accompanied by a prominent increase in eosinophils on the surface of the nasal epithelium, an increase that correlated strongly to the degree of pollen exposure and symptoms experienced by the patients. Thus, human in vivo data point to, at least to some extent, similar cellular changes in the laboratory following a local challenge and the clinical disease of hay fever.