NOS2 and pulmonary emphysema: Structural data obtained by design-based stereology to quantify the emphysema-like phenotype and disturbances of the intracellular surfactant were correlated to invasive pulmonary function tests and inflammatory markers including activation markers of alveolar macrophages and compared to SP-D (Sftpd−/−) and iNOS single knockout mice (NOS2−/−) as well as wild type (WT) littermates.