Antibodies were found in the blood of certain rabbits carrying one or another of four transplanted cancers (Brown-Pearce and V2 carcinomas; RSI and Kato sarcomas) which will fix complement in vitro in mixture with saline extracts of various normal and neoplastic rabbit tissues—including liver, kidney, spleen, and the four tumors mentioned—and chick embryo tissue as well. These antibodies, which have been called induced tissue antibodies, are similar to the natural antibodies previously described (2) in that they react with those constituents of the various tissue cells that prove readily sedimentable in the high speed centrifuge; they differ from the natural antibodies in being absent from the blood of normal rabbits and in withstanding 65° C. for 30 minutes.
Certain quantitative differences suggest that the induced tissue antibodies have somewhat various affinities, depending in part upon the type of neoplasm carried by the host. They may perhaps be consequent on antigenic differences between the sedimentable constituents of the tumor cells and those of the new hosts; for they were not found in the blood of rabbits carrying papillomas and cancers composed of the animals' own cells, and not in that of rabbits in which multiple vaccinia or fibroma virus lesions had recently regressed.
The characters of the sedimentable constituents of normal and neoplastic tissue cells, as revealed thus far by chemical, morphological, and serological studies, have recently been discussed (2,8). In this relation, it has seemed essential to recognize the induced antibodies here described, particularly since they may complicate serological studies aimed at disclosing distinctive sedimentable substances in tissue cells. In an associated paper experiments are reported which bear upon the relation between the induced tissue antibodies and an antibody that reacts specifically with a distinctive sedimentable constituent of Brown-Pearce carcinoma cells (7).