Substance P immunoreactive nerves in airways from asthmatics and nonasthmatics

Substance P has been localized to nerves supplying smooth muscle, blood vessels and glands in the human lung and may play a major role in the pathophysiology of asthma. We performed a morphological study, using the avidin biotin peroxidase immunostaining technique, to examine sections of airway wall from subjects with and without asthma for the presence of substance P immunoreactive nerve fibres. Airways of 200 microns-12 mm were obtained from autopsy, lobectomy and bronchoscopy. Quantitative morphological analysis was performed on 3 mm diameter airways from three asthmatic and three nonasthmatic subjects collected at autopsy, and on biopsies of 10 mm diameter airways from eight asthmatic and thirteen nonasthematic subjects. There was an increase in both the number and the length of substance P immunoreactive nerve fibres, in airways from subjects with asthma when compared with airways from subjects without asthma. Fibres were found in the lamina propria and surrounding vessels and glands. The fibres were commonly seen as bundles rather than as single fibres. There was no difference in the number of substance P nerves between normal subjects and subjects with chronic airflow limitation (CAL). The difference in the number, length and morphological characteristics of the substance P immunoreactive nerves between asthmatic and nonasthmatic subjects were striking.