IMMUNOHISTOCHEMICAL STUDIES ON HUMAN COLONIC TUMORS:

With Special Reference to Secretory Component Localization and IgATransport Mechanism

Abstract

The peroxidase-labelled direct antibody method after Nakane was used for the localization of secretory component (SC) andIgAin colonic tumors and related disorders, e.g. adenocarcinoma, adenoma and hyperplastic polyp.SCwas found in identical ultrastructural sites in adenoma or hyperplastic polyp epithelium as in the epithelium from normal subjects, i.e. the perinuclear spaces, cisternae of the rough endoplasmic reticulum, lamellae and vesicles of the Golgi complexes, basolateral plasma membrane (but not apically beyond the tight junctions) and vesicles in the cytoplasm. The immunohistochemical characteristics ofSC, i.e. amount and localization in adenomas and hyperplastic polyps, are closely aligned with those of the normal colonic mucosal epithelia showing maturity of varying degrees. That is, the epithelia of adenomas exhibit immaturity, whereas those of hyperplastic polyps indicate hypermaturity. For instance, the immunoelectron microSCopic observation revealed that the immature goblet cells in adenomas exhibited SC synthesis, while mature goblet cells contained littleSCin their cytoplasm. These results suggest that SC could be a good indicator for maturation and differentiation of colonic epithelial cells. In contrast to those benign tumors, the staining intensity and intra-and extra-cellular fine localization of SC were quite variable from cell to cell in adenocarcinoma. In the adenocarcinomasSCwas demonstrated not only on apical plasma membranes and the surfaces of microvilli of the neoplastic cells, but also in the epithelial interstices and surrounding connective tissues. These immunohistochemical observations provided a morphological evidence of "loss of polarity" in malignant cells. Although theSC-mediatedtransportmechanism for dimericIgAwas rather well maintained in these colonic tumors, tranSCellulartransportfor sIgAthrough the neoplastic cells was on occasion retarding.