Heterogeneous proliferation of type II pneumocytes in usual interstitial pneumonia.
OBJECTIVE
Heterogeneous alveolar fibrosis, the most specific pathological finding in idiopathic pulmonary fibrosis (IPF)/usual interstitial pneumonia (UIP), enables differentiation of UIP from other interstitial pneumonias. Heterogeneous and mild alveolar injury may occur, and this will be a clue to clarifying the pathogenesis of UIP.


METHODS
We examined nine lung biopsy specimens obtained from patients with IPF and five control specimens. We semi-quantitatively examined alveolar injury by measuring the density of type II pneumocytes. Serial 3 microm sections were stained with anti-Thomsen-Friedenreich (TF) antibody. We divided each UIP lesion into three areas: area near fibrosis (fibrous area), area with an apparently normal alveolar structure (normal area), and area between the fibrous and normal areas (intervening area).


RESULTS
Immunostaining with anti-TF antibody stained the apical surface of type II pneumocytes and enabled us to recognise and count type II pneumocytes. The density of type II pneumocytes was increased in the fibrous area, and gradually decreased away from the fibrous lesion. The densities of type II pneumocytes in the above three areas were, respectively: 13.9+/-2.0, 7.2+/-1.6, and 9.5+/-1.6/mm alveolar length. The densities in the fibrous and intervening areas were significantly greater than those in the normal area and in control specimens (6.6+/-0.7/mm).


CONCLUSIONS
If the density of type II pneumocytes indicates their degree of regeneration after alveolar injury, it reflects the severity of the pre-existing injury. This study confirms that heterogeneous and mild alveolar injury occurs in UIP.
Honda
Takayuki
T
Department of Laboratory Medicine, Shinshu University School of Medicine, Matsumoto, Japan. thondat@hsp.md.shinshu-u.ac.jp
Uehara
Takeshi
T
Sano
Kenji
K
D000328:Adult; D000368:Aged; D000906:Antibodies / Q000032:analysis; D001706:Biopsy; D001784:Blood Gas Analysis; D002452:Cell Count; D049109:Cell Proliferation; D005260:Female; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000097:blood; D008168:Lung / Q000473:pathology* / Q000502:physiology; D017563:Lung Diseases, Interstitial / Q000150:complications / Q000276:immunology / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011650:Pulmonary Alveoli / Q000473:pathology*; D011658:Pulmonary Fibrosis / Q000209:etiology / Q000473:pathology*; D012038:Regeneration; D012129:Respiratory Function Tests
D000906:Antibodies; C025991:Thomsen-Friedenreich antibodies; D007770:L-Lactate Dehydrogenase