Immunohistological identification of epithelioid cell granulomas in Crohn\u27s disease and its diagnostic values especially in the differentiation from ulcerative colitis

We produced a monoclonal antibody against epithelioid cell granulomas (ECGs) by immunizing mice with a crude tissue extract of lymph nodes with sarcoidosis. The established antibody (ECM antibody) strongly reacted with epithelioid cells and Langhans\u27 type giant cells of ECGs not only in cases of sarcoidosis, but also in cases of other granulomatous diseases such as tuberculosis and Crohn\u27s disease. In this study, we used the ECM antibody to improve the histopathological diagnosis of Crohn\u27s disease, in which the demonstration of ECGs is critical for diagnosis, but morphological identification of ECGs by hematoxyline and eosin (HE) staining is frequently difficult. When we examined the tissues removed at operation from 11 patients with Crohn\u27s disease, we observed a total of 29 lesions of morphologically recognizable ECGs, all of which were immuonohistologically positive for the ECM anti­body (granuloma pattern). In addition the ECM antibody revealed 43 nests of tiny inflammatory lesions (nested pattern) that could not be morphologically recognized as ECGs by HE staining only. Both the granuloma and nested patterns of ECM immunoreactivity were present in all cases of Crohn\u27s disease we examined, but were absent in all 15 cases of ulcerative colitis that were used as controls