Reduction of the immune resistance in male and female mice to pneumonia after ozone exposure: histopathologic assessment of risk factors

It is known that ozone, a key ingredient of smog in the cities, is one of the critical anthropogenic air pollutants. Ozone exposure impacts the pneumonia course. We have shown before that although female mice were more resistant to pneumonia than males, ozone exposure made them more susceptible. The aim of this work was to study the mechanisms of these trends by the histopathologic evaluation of the risk factors for pneumonia after ozone exposure. The results showed: 1) the severity and the area of the lung inflammation were higher and the red pulp spleen myelopoesis was lower in mice of both sexes after ozone exposure and pneumonia compared to control; 2) more pronounced extrapulmonary lesions (in liver and spleen) were detected in filtered air-exposed and infected males compared to females; 3) more severe lung inflammation was found in ozone-exposed and infected female mice compared to males. Thus, different risk factors contributes into the different outcome of pneumonia in different sexes depending on the presence or absence of oxidative stress caused by ozone exposure: excessive lung inflammatory response in females after ozone exposure, and the higher risk for extrapulmonary lesions in males after filtered air exposure.