Studies on the relationship between sarcoma and leukosis in chickens; tumor induction by intramuscular injections of cell-free and cell-containing material from of pure leukosis strain.

It has been reported that some strains of transplantable fowl leukosis are capable of inducing sarcomas at the site of inoculation when suitable material is injected intramuscularly or subcutaneously. Observations on this subject have been published bv Oberling and Gu&in (] 8,19, 20), Rothc Meyer and Engelbreth-Ilolm, for strain E.S., (22, 6), Stubbs and Furth, for strain 13, (2~). Histologically, the growths that arise with great regularity as a result of the inoculation of lcukotic material are spindle cell and polymorph cell sarcomas; they may also present the aspects of endotheliomas or angiocndotheliomas. The tumors develop fairly rapidly and may reach a considerable size. They can produce metastases and can be in most cases readily transplanted from fowl to fowl. The growths may also be induced by inoculation of cell-free leukotic material. The tmnors arc in most cases associated with leukosis, but may also appear alone. All such strains originated in chickens which had neoplasms in addition to some form of leukosis. It is generally assumed that in the ease of the strains mentioned above the combined effect is caused by a single agent, originally capable, or becoming capable in the course of passage, of attacking not only primitive blood cells, but also other cell elements of the mcsenchyme. Besides these "combined" strains of leukosis, i.e. strains which are equally able to stimulate blood cell precursors and fixed mcsenchymal cells to unrestricted growth, there arc also leukotic strains more specifically adjusted. Thus, Stubbs (24) describes a strain of ]eukosis which never produced sarcomas after intramuscular or subcutancous inoculations. Mohos' (17) erythroleukemic strain was also unable to produce sarcoma. Furth (7, 8) reported a strain of lcukosis (strain 1) which after intramuscular inoculation led to sarcomas only in exceptional cases. 1 Uhl, Engelbreth-Hohn and Rothe Meyer (27) studied two lcukotic strains R. and T., which in contrast to their strain E.S., rarely led to tumor formation after intramuscular or subcutaneous inoculation. Strains of leukosis which never or relatively rarely cause new growth were designated "purc" strains. Uhl, Engelbreth-Itohn and Rothe Meyer (27) stressed the point that the tumors that occasionath' arise after inoculation of material from their socalled "pure" strains of leukosis differ from those devcloping after the inoculation of "combined" strains not with rcspect to their frequency alone. Sarcomas which appear after the inoculation of "pure" strain material had a rcmarkably low growth capacity. Mctastases were never observed. The transfer of such tumors was seldom successful and when feasible only one passage could bc carried out. From the reported observations it seems plain that different lcukotic strains vary greatly in their ability to cause tumors, beginning with strains which have no tumor-producing capacity at all, and ending with those which constantly give rise to tumors as well as leukosis. It seems likcly that in these extreme cases we are dealing on the one hand with an agent having special affinity for one definite type of cell (primitive blood cell) and this cell only, and on thc other hand with an agent cqually capable of attacking various cell elcmcnts of the mesenchyme.