A novel diagnostic method for pulmonary aspiration in a murine model - Immunocytochemical staining of milk proteins in alveolar macrophages

Aspiration of foreign material into the lungs has been implicated in the et iology of a variety of pulmonary disorders. Although aspiration is a common clinical problem, its diagnosis represents a major challenge due to the la ck of sensitive and/or specific tests. In this study, we evaluated the sens itivity and specificity of a novel diagnostic method in a murine model of m ilk aspiration, Under light anesthesia, BALB/c mice received either single or repeated intranasal instillation of milk. Control animals received steri le physiologic saline or were infected with respiratory pathogens in a simi lar manner, After isolation and cannulation of the trachea, mouse lungs wer e lavaged with PBS at various time points after the last aspiration event. Cells were recovered for Oil Red O (ORO) staining as well as immunocytochem istry for milk proteins: alpha-lactalbumin and beta-lactoglobulin. After si ngle aspiration of milk, a large number of alveolar macrophages displayed a strong immunoreactivity for alpha-lactalbumin for 2-96 h. After single and repeated aspiration, the percentage of positive cells for alpha-lactalbumi n was significantly higher when compared with ORO staining at 24, 48, and 7 2 h (p < 0.05). No immunoreactivity for milk proteins was found in alveolar macrophages obtained from our control groups. These findings demonstrate t hat immunocytochemical staining of milk proteins within alveolar macrophage s represents a novel, sensitive, and specific test for the diagnosis of asp iration In a murine model.