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 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 sparsely brown stained fibrillin (1) in the thin alveolar septa and fragmented tips (↓). (3) Indicate capillaries in the septal wall. At (X) brown-stained fibrillins associated with elastic membranes are still found in an intact small pulmonary artery. During the severe course of emphysema the decrease and fragmentation of fibrillin is progressive. Therefore the antifibrillin antibody marks the gravity of destruction of the alveoli during emphysema.