Immunohistochemical analysis of LNT, NeuAc2----3LNT, and Lex carbohydrate antigens in human tumors and normal tissues.

Monoclonal antibodies (MAbs) K21 and K4 define two carbohydrate determinants, lacto-N-tetraose (LNT) and sialylated LNT (NeuAc2----3LNT). respectively, which are expressed on the surface of cultured human teratocarcinoma cells, but not on a wide range of other epithelial and nonepithelial cells in culture. The present study used immunohistochemical methods to examine LNT and NeuAc2----3LNT expression in normal human tissues, 29 germ cell tumors, and over 200 tumors of other histologic types. In addition, their distribution was compared with that of Lex, a previously characterized cell surface carbohydrate antigen. Our results show that LNT and NeuAc2----3LNT are consistently expressed in germ cell tumors and that each has a distinct, highly restricted distribution in normal tissues. LNT and NeuAc2----3LNT expression in germ cell tumors is predominantly localized to embryonal carcinoma and yolk sac components, whereas Lex is found primarily in teratoma components with intestinal and bronchial differentiation. Areas of seminoma variably express NeuAc2----3LNT and LNT but are Lex-negative. Immunohistochemical results obtained with different fixation procedures suggest that some cell types in vivo express NeuAc2----3LNT, LNT, and Lex determinants only on glycolipids, whereas other express them on both glycolipids and glycoproteins or only on glycoproteins. Thus, the tissue distribution of these antigens may be controlled by differential expression of the requisite glycosyltransferases as well as the availability of different classes of carrier molecules.