Monoclonal antibodies to epithelial sialomucins recognize epitopes at different cellular sites in adenolymphomas of the parotid gland.

Fourteen monoclonal antibodies (MAbs) to epithelial sialomucins were studied for their immunohistochemical reactivity on serial sections of 14 formalin-fixed and paraffin-embedded adenolymphomas of the parotid gland. Two types of reactivity were observed, suggesting different cellular distribution of the corresponding epitopes. Most antibodies reacted with the luminal membrane of the columnar tumor cells (type-A reaction). The other reaction (type B) was observed with the membrane of basal epithelial cells. The antibodies could be ranked according to their tendency to show type-A and/or type-B reactions. MAb Cal was the only one with a pure type-A reaction. A strong tendency to type-A reactivity (with traces of type-B reactions) was observed for the antibodies HMFG-2, M8, E29 and NCRC-II. Several antibodies gave good type-B reactions in addition to strong type-A reactivity (MAbs 126E7, 115G2, 115D8, 140C1, F36/22, 139H2). MAb DF3 showed equally strong reactions with both cell types. A clear-cut preference of the reactions with basal cells was seen with the antibodies HMFG-1 and 115F5. This subclassification of the antibodies is in accordance with epitope mapping data, obtained by conventional blocking studies reported in the literature.