Absence of reaction of a xenogenic anti-h-2 serum with mouse embryonal carcinoma cells.

SUMMARY A rabbit antiserum raised against papain-solubilized H-2 antigens has been used to investigate the eventual expression of H-2 antigens and related molecules on embryonal carcinoma cells and on other types of mouse cells. No material reacting with this serum could be detected on cells carrying the F9 antigen. It is concluded that no H-2 antigen or cross-reacting material is expressed on these cell types. SUMMARY Teratocarcinomas are malignant tumors which are characterized by the presence of a variety of differentiated tissues, plus embryo-like cells called embryonal carcinoma (EC) cells (8, 44). These EC cells are the stem cells from which differentiated types derive in tumors (35, 36). Several lines of EC cells have been established in vitro, and are now propagated as clonal cultured cell lines (27, 32). Because of their homology with early embryonic cells (8), their ability to differentiate in vitro along a reproducible pattern (27, 32, 33), and mostly because of their cell surface characteristics (22, 43), several lines of EC are now increasingly used for various immunological studies (16, 19, 41, 50). EC cells display at their surface an early embryonic antigen (the F9-antigen) (3, 22), which appears to be related to the T locus system (2, 22, 25), and the structure of which seems to be similar to that of H-2 antigens (47). H-2 antigens appear not to be expressed on EC cells (4, 10, 16, 17, 22, 47, 50). However, it has been suggested that EC cells might carry some precursor (11, 20) or some modified form of H-2 antigens. SUMMARY We have therefore studied the expression of cell surface material cross-reacting with the heavy chain of H-2 antigens, on several lines of embryonal carcinoma. A xenogenic anti-H-2 serum was used in these studies. This antiserum was obtained by immunizing rabbits with purified papain fragments of H-2 antigens (31). It has been shown to react with the core molecule of all H-2 antigens, irrespective of their genetic haplotype. Furthermore, as shown in this paper, it reacts also with the major histocompatibility complex (MHC) products of various mammals. With this serum, it is therefore possible to investigate the expression of H-2 antigens and of cross-reacting material on embryonal carcinoma cells and their differentiated derivatives.