Chapter 4. 



Immunity and Organismal Differentials 

 in Tumor Transplantation 



In the preceding chapters we have analyzed the relation between the 

 transplantability of tumors and the genetic constitution of the organisms 

 in which the tumors originated, as well as of the hosts, and the indi- 

 viduality and species differentials of these organisms. It has been stated 

 already that also immunity against cancer grafts may be an expression of 

 the organismal differentials and from this point of view various aspects 

 of this type of immunity will now be considered. We shall study, therefore, 

 mainly those phenomena in immunity which have a bearing on the role 

 which organismal differentials play in tumor growth, in particular, the con- 

 stituents of strange organismal differentials which may readily function as 

 antigens and thus induce immunity against grafted tumors. 



Early investigators in this field, Jensen, Ehrlich and Apolant, Bashford 

 and Murray, applied the principles established in the study of immunity 

 against microorganisms, animal cells and proteins to the study of immunity 

 against transplanted cancer. At an early stage of these investigations, a nat- 

 ural immunity and an acquired immunity to microorganisms and their 

 toxins were distinguished. By natural immunity is understood a preformed 

 constitutional resistance. The development of an active immunity, on the 

 other hand, presupposes a previous interaction between the host organism 

 and the strange cells or substances against which the immunity is acquired. 

 In active immunity, substances (immune substances, antibodies) may be 

 produced, which circulate in the bodyfluids of the host and tend to injure the 

 strange cells or to neutralize those substances (antigens) which elicited the 

 immune reaction. By injecting these bodyfluids of the actively immunized 

 animals into other animals it is possible to transfer the immunity to the 

 latter, which thus acquires a passive immunity. We have already discussed 

 some of the conditions on which depends the existence or lack of natural 

 immunity to the growth of transplanted tumors, namely, the relations be- 

 tween the constitutional genetic factors in the tumors, which are to be 

 transplanted, and in the hosts, into which they are to be transferred; the 

 latter may be individuals of the same strain or species in which the tumors 

 originated, or individuals of different strains or species. The resistance to 

 homoiogenous or heterogenous transplantation may thus be considered pri- 

 marily as a manifestation of natural immunity, which depends on the relation 

 between the individuality and species differentials of the host and transplant. 

 Especially striking in this connection are the differences between the results 

 of auto- and homoiotransplantation. Here, reference may again be made to 

 the experiment in which Fleisher and the writer showed that the immunity 



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