IMMUNOHISTOCHEMICAL CHARACTERIZATION OF A PANEL OF 56 ANTIBODIES WITHNORMAL HUMAN SMALL-INTESTINE, COLON, AND BREAST TISSUES

The epithelial mucin MUC1 is heavily but differently glycosylated depe nding on the origin and developmental status of the tissue. which grea tly influences the reactivity of monoclonal antibodies (MAbs). A parti al characterization of their epitopes is possible by mild, carbohydrat e-specific periodate oxidation of tissue sections prior to immunostain ing. Using this strategy, we have evaluated 56 MAbs submitted to the I SOBM TD-4 (MUC1) Workshop. Paraffin sections from normal human small i ntestine, colon and breast were immunostained at different defined ant ibody concentrations either directly or after oxidation with 20 mM per iodate at pH 5 for 30 min (PO). In addition, monolayers of T-47D breas t cancer cells without PO treatment were examined in immunofluorescenc e. The array of observed reactivities allowed us to classify the MAbs as follows. Fourteen antibodies were Found to detect MUC1 largely inde pendent of the degree of glycosylation, and are therefore classified a s pan-h MUC1 MAbs (Group A). Twenty-four MAbs were nonreactive with on e or more types of the examined epithelia, but became reactive after P O of the tissue sections. We have called these differentiation-depende nt MUC1 MAbs (Group B). They might be especially valuable in histologi cal tumour diagnosis. According to their differential staining behavio ur towards untreated small intestine, colon, and breast tissue section s, we divided these MAbs into 4 subtypes (Group B1 through Group B4). A further group of six MAbs detected PO-sensitive carbohydrate epitope s (Group C). A seventh antibody apparently also belongs to Group C by immunohistological criteria, although its corresponding epitope was no t PO-sensitive. Three further MAbs are still unclear in their specific ity, and another 2 are not MUC1-specific (Group D). Six preparations w ere found nonreactive with the examined tissues; 4 of these were also negative with T-47D cells. Generally a broad spectrum of different imm unohistological patterns has emerged which appears to be widely indepe ndent of the type of epitope (sequence versus conformational. length o f sequence) and the relative affinities determined in vitro.