Immunohistochemical classification of the localization of laminin in the thickened bronchial epithelial basement membrane of deceased bronchial asthma patients.

Abstract To ascertain histological changes in the basal lamina of the bronchial epithelial basement membrane in patients with severe bronchial asthma, an immunohistochemical study was conducted in 43 patients who died of bronchial asthma. Antibodies against laminin, a component of the lamina lucida, were utilized. The results revealed various patterns for immunoreactivity to laminin in the thickened basement membrane layer. We were able to classify these reactivities into four patterns. In Pattern A, laminin reactions branched vertically in relation to the thickened basement membrane layer. In Pattern B, laminin reactions formed lines along the lower margin of the thickened basement membrane layer. In Pattern C, laminin reactions formed lines along the upper margin of the thickened basement membrane layer. Finally, in Pattern D, no laminin reactions were observed. In addition, relationships between immunohistological characteristics of laminin and findings such as epithelial cell shedding, basal cell proliferation and basement membrane layer thickening were investigated. In many Pattern A patients, epithelial cell shedding was observed, but goblet cell hyperplasia and basal cell proliferation were barely detectable. Conversely, in numerous Pattern D patients, epithelial cell shedding was barely seen, but goblet cell hyperplasia and basal cell proliferation were marked. Hence, Patterns A and D were on opposite ends of the spectrum of morphological characteristics associated with severe bronchial asthma. In Patterns B and C, laminin reactions formed lines along the lower and upper margin of the thickened basement membrane layer, respectively. However, no marked differences existed in epithelial cell shedding and basement membrane layer thickening. The present study is thus the first to clarify that laminin reactions in the thickened basement membrane layer vary, and this feature is unique to the bronchi of patients with severe bronchial asthma.