The inactivation in vivo of mouse lymphosarcoma 6C3HED by antibodies produced in a foreign host species.

In the past, several workers have reported that neoplastic tissues possess antigenic differences from normal tissues and that these differences can be demonstrated by immunological methods. Gen eral reviews of this field have been published (6, 9, 12). One technic that has been used has been the in vitro neutralization test similar to that employed for the immunological study of viruses. Using this general approach, Dulaney and Arnesen (2) have shown that antisera to components of both normal and leukemic cell exhibit in vitro cytotoxic effects for mouse leukemic cells, but that the leukemic antisera were much more effective than normal tis sue antisera. More recently, Werder, Kirschbaum, MacDowell, and Syverton (10, 11) have shown that granulocytic and lymphocytic mouse leuke mic cells are inactivated in vitro more readily by antibodies produced in rabbits against the leuke mic cells than by antinormal tissue sera. Green (5) found that rabbit antiserum prepared against mouse mammary tissue containing the milk factor possesses cytotoxic properties for mammary car cinoma cells when mixed with them in vitro. How ever, Law and Malmgren (8) have recently re ported no consistent difference in the protective action of rabbit tumor antisera and those against normal tissues free of the tumor agent. Kidd (7) has shown that there is an antigenically distinct, sedimentable substance present in the BrownPearce rabbit carcinoma and that this substance is not detectable in a variety of normal rabbit tissues or in three other types of rabbit tumors. Also, from the results of experiments carried out by Burmester (1) with the avian lymphoid tumor, it appears that there is a factor, or factors, present in tumor tissue which is antigenically different from con stituents of normal lymphoid tissue. It is the purpose of this paper to record the re sults of experimental studies demonstrating that specific antibodies can be produced in a foreign