Fibrillin in the alveoli of lung emphysema (human, adult)

Stain: antifibrillin antibody immunoperoxidase staining with diaminobenzidin reaction. Fibrillin is one of the elastin-associated microfibrillar proteins, and marks therefore also the presence of elastin in lung tissue. In centrilobular emphysema (e.g., in lungs of smokers) the lesions are more common and severe in the upper lobes i.e., the air spaces are dilated and chronic inflammation is found around bronchi and bronchioli. There is an imbalance between protease and antiprotease activities in the lung. Upon stimulation by, among others, cigarette smoke, macrophages (M) and neutrophilic granulocytes release elastase out from their lysosomes. In this way the initiation of tissue destruction starts, alveoli are broken down and the result is a permanent enlargement of the air spaces with the breakdown of elastin. The immunostaining then reveals the brown-stained fibrillin (1) as short brittle deposits closely associated with the white (unstained) elastin fibers (2). Within the thickened septal wall (↔) fibrillin also appears irregular and found in decreased amounts. During the severe course of emphysema the decrease and fragmentation of fibrillin is progressive. Therefore the antifibrillin antibody marks the gravity of tissue destruction during emphysema.