Asthma is a disease characterized clinically by reversible obstruction of the airways, or bronchi, and bronchial nonspecific hyperresponsiveness, the tendency of the bronchi in asthmatics to constrict in a response to a wide range of specific and nonspecific stimuli. It is now widely accepted that chronic inflammation of the bronchial mucosal lining plays a fundamental role in the genesis of these clinical manifestations. The most striking feature of this inflammation is the intense infiltration of the bronchial mucosa with eosinophils, macrophages, and lymphocytes (I). It will be seen later in this chapter how cytokine and chemokine products of activated T-LC have the propensity to bring about this selective
eosinophil accumulation and activation. The eosinophil in turn appears to be a key cell in producing injury to the bronchial mucosa (Chapter 14), which is believed to result in bronchial obstruction and irritability, although the precise mechanisms by which this occurs are not clear.