Mast cells and allergic rhinitis

Abstract

Large scale surveys in general practice have indicated that the prevalence of hay fever is 4% and that the disease has becane more conmon in recent years. Patients attending their general practitioners for treatment prdbably represent less than half of those who suffer from the disease as many afflicted by seasonal rhinitis treat themselves. The disease is equally ccmmon in both sexes, its incidence being highest between the ages of 15 and 25 years [1]. While studies from Japan suggest that the increase in prevalence of allergic rhinitis may be related to air pollution fran diesel engines, a 23 year follcw-up study of 17,414 children bom in one wed<: of March 1958 indicated that hay fever was strikingly more camon in first bom children and less catmon in subsequent siblings, particularly in large families. Cross infection is frequent amongst younger children in large families and it is possible that such infections in some way decrease the likelihood of the subsequent development of allergic disease [2], It is new clear that the instillation of allergen into the nose provokes an immediate nasal response canmencing within minutes and lasting for up to an hour, which is followed in approximately 50% of allergic rhinitics by the development of a late phase response with a variable time of onset between two and eight hours. Although the pathogenesis of the immediate nasal response is well defined, mechanisms leading to the development of late phase reactions remain to be determined.THE MAST CELL 1 Studies on the release of histamine and particularly prostaglandin D2 (PGD2) and tryptase into secretions during the immediate nasal response have confirmed the critical role of the mast cell in the developrrent of the immediate symptoms of nasal allergy. There is a greater density of metachrcinatically staining cells in the nasal epithelium of patients with allergic rhinitis ccmpared to non-rhinitics and the number of these cells Increases during natural allergen exposure. Whether these metachrcmatically staining cells are basophils or mast cells remains controversial as does the finding of an increasing number of mast cells in the lamina propria of allergic rhinitics over the course of the pollen season [3], The increase in the ntJiriber of metachrcmatically staining cells in both the nasal epithelium and lamina propria can be prevented by treatment both with topical corticosteroids and with nedocrorail sodixim 13]-I

Effects of H1‐receptor antagonists on nasal obstruction in atopic patients

“…Previous studies have shown that the appearance of mediators, such as histamine, leukotrienes (B4, C4), and prostaglandins (D2), is followed by the typical hay fever symptoms of rhinorrhea, sneezing, itching, and nasal obstruction (6). These findings are consistent with mast cell degranulation (4). Specific provocation with histamine only also leads to the same symptoms, but within seconds (11).…”