Diffuse alveolar damage and acute interstitial pneumonitis: histochemical evaluation with lectins and monoclonal antibodies against surfactant apoprotein and collagen type IV.

Diffuse alveolar damage (DAD) and acute interstitial pneumonitis (AIP) often present clinically as the adult respiratory distress syndrome. To evaluate the usefulness of histochemical techniques and to better understand the histopathologic changes of these diffuse lung injuries, postmortem lung sections of 14 and 33 patients who had been diagnosed as having DAD in organizing stage and AIP, respectively, were studied with the use of lectins and monoclonal antibodies against surfactant apoprotein (PE-10) and collagen type IV. On hematoxylin-eosin stained sections, type II pneumocyte hyperplasia and hyaline membrane formation were the major histopathologic findings in both DAD and AIP. The binding rates of type II pneumocytes to Ulex europaeus agglutinin I (UEA-I) in both DAD (64%) and AIP (45%) cases were significantly higher than those of type I pneumocytes or alveolar macrophages (both P < 0.001). Reactions of type II pneumocytes to PE-10 varied from 40 to 44% in DAD and 0 to 100% in AIP cases depending on the use of respirator and steroid medication. Therefore, it may be said that UEA-I and PE-10 are useful methods for outlining hyperplastic type II pneumocytes in both DAD and AIP. Hyaline membrane coating alveolar septal surfaces and exudate in alveolar air spaces were also stainable with PE-10. Surfactant apoprotein remained demonstrable histochemically within type II pneumocytes and hyaline membrane despite severe inflammatory injuries of the lungs. The immunohistochemical stain using anti-collagen type IV antibody revealed discontinuous alveolar basement membrane in 50% of DAD patients with respirator use and 80% of AIP patients with steroid medication.