To clarify the immunological characteristics of small airway areas, an unlabelled antibody peroxidase method for the detection of IgG, IgA, IgM, IgE & complement (C(1)q) was applied to human peripheral lung tissues from patients with or without immunological respiratory diseases. Normal lung tissues were obtained from 8 surgically resected lungs with primary carcinoma.
In normal peripheral lungs, immunoglobulin containing cells were mainly distributed around the bronchiolar mucosa, but were sometimes found in alveolar septa. IgA containing cells were most numerous (mean 64.6%), followed by IgG containing cells (mean 20.1%) and IgM containing cells (mean 13.7%). IgE containing cells were virtually absent from small airway areas. No interstitial deposition of immuoglobulins or complement was detected in normal peripheral lung tissues.
In peripheral lungs with interstitial lung diseases, immunoglobulin containing cells were generally increased in number compared with normal lungs. Among them, IgG containing cells were dominant especially in interstitial pneumonia cases. In peripheral interstitium, various immune depositions were observed. Marked IgG and C(1)q deposits were seen in thickened septa of interstitial pneumonia and around granulomas of sarcoidosis, suggesting a relation between immune complex and these diseases. In diffuse panbronchiolitis, there were many IgG containing cells around the bronchiolar area. These findings indicate that the IgA antibody was dominant in the immunological defence mechanism of the normal peripheral lung, whereas IgG antibody and complement as well as IgA antibody were important in immuological respiratory diseases.