Late-phase airway reaction and inflammation

With some exceptions, the late asthmatic response and increased airway responsiveness to methacholine or histamine are closely associated. Increased responsiveness after an allergen challenge can be reversed or prevented by appropriate anti-inflammatory treatment. To determine how the inflammatory response contributes to an increase in smooth muscle responsiveness in asthma, local hematopoietic processes were examined. In support of the mast cell hypothesis, scrapings from nasal turbinate mucosa have shown greater numbers of mast cells in patients with allergic rhinitis compared with normal subjects. Similarly, the number of metachromatic cells in bronchoalveolar lavage fluid correlates directly with methacholine-induced airway hyperresponsiveness. Since nasal polyps appear to result from inflammation of nasal mucosa, these tissues were also examined for the possible presence of progenitor cells that favor selective growth of basophil/mast cells. Since growth factors such as interleukins and cytokines stimulate cell activation, they may also contribute to ongoing inflammatory processes. Therefore substances that modify the production or actions of locally generated growth factors might be developed for the treatment of chronic inflammation of the nasal and bronchial airways.