The Role of Tolerance in Pulmonary Defense Mechanisms

Abstract

Exposure to ozone (O₃) produces tolerance against the formation of pulmonary edema. Littie evidence is available regarding the development of tolerance to O₃ In other endogenous defense mechanisms of the lung. A unilateral lung exposure technique was employed to show the effects of prior O₃ challenge on edema formation, the absolute numbers, viability and hydrolytic enzyme activity of alveolar macrophages (AM), and the absolute number of polymorphonuclear leukocytes (PMN). Statistical analysis of the data showed that the initial O₃ exposure induced a tolerance against pulmonary edema but that no protection was afforded against the cytotoxic effects of O₃. On the contrary, the numbers, viability, and markedly reduced enzymatic activities of AM were equal In both tolerant and nontolerant lungs; and inflammation, measured by the presence of PMM, was increased two-fold in the tolerant lung.