[Immunohistochemical study of KL-6 in pulmonary tuberculosis]

KL-6 is a glycoprotein antigen derived from the cell line of human lung adenocarcinoma. Although KL-6 is known to be a serum marker of interstitial pneumonia, elevated KL-6 serum levels have also been reported in some cases of pulmonary tuberculosis. To elucidate the mechanism of KL-6 elevation in pulmonary tuberculosis, we stained pulmonary tissue samples from five clinical cases for immunohistochemical analyses. In the two cases showing productive changes, KL-6 immunoreactivity was localized in the area of type II pneumocytes showing strong interstitial changes surrounding caseous necrosis. In the two cases showing exudative changes, KL-6 immunoreaction was observed not only to surround caseous necrosis but also to appear within it, particularly in the remaining alveolar lumen septa. On the other hand, the one patient with old pulmonary tuberculosis that showed slight interstitial changes presented with weak KL-6 immunoreactivity on the surface of the alveolar lumen surrounding the tuberculotic region. These results suggest that serum elevation of KL-6 in pulmonary tuberculosis originates from the proliferation of type II pneumocytes along with interstitial changes that surround the tuberculous region.