TENASCIN IMMUNOREACTIVITY IN CRYPTOGENIC FIBROSING ALVEOLITIS

Tenascin is a hexameric extracellular matrix (ECM) glycoprotein which has been demonstrated to have a temporal relationship with active scar formation in adult tissues. We hypothesized that this ECM protein mig ht therefore serve to identify areas of active scarring in lung biopsi es from patients with cryptogenic fibrosing alveolitis (CFA). The dist ribution of tenascin was examined in open lung biopsies from ten patie nts with CFA, six patients with sarcoidosis, and six pulmonary resecti on specimens from patients with no evidence of interstitial lung disea se, using an immunohistochemical technique. Immunoreactive tenascin wa s not identified in histologically normal control lung parenchyma and was only focally found around large aggregates of granulomas in sarcoi dosis. In the CFA, tenascin production was demonstrated in minimally d amaged alveolar walls and areas of active disease but not in end-stage scarred lung. There was considerable local heterogeneity of staining within cases, which did not appear to relate to the density of the loc al inflammatory infiltrate. Large plaques of tenascin were noted to be particularly associated with hyperplastic type II alveolar epithelial lining cells, which are recognized to produce fibrogenic cytokines. T he examination of tenascin expression in open lung biopsies from patie nts with CFA may be useful in assessing fibrogenic activity and may th us provide additional prognostic information.