Specificity: 139H2 reacts with MUC1, a large transmembrane glycoprotein expressed on the ductal surface of normal glandular epithelia. The dominant epitope of 139H2 has not yet been determined. In immunohistochemical assays, it superbly stains routine formalin/paraffin carcinoma tissues. An antibody to MUC1 is useful as a pan-epithelial marker for detecting early metastatic loci of carcinoma in bone marrow or liver. Immunogen: Human milk-fat globule membranes