Chapter 5 



On the Differences between the Reactions of 



Foetal or Newborn Organisms and of Adult 



Organisms Against Strange Differentials as 



Established by Serological Methods 



In a preceding chapter we have discussed the differences in reactions 

 between very young and older guinea pigs or of embryonal organisms 

 against various homoiotransplanted tissues. The reactions against foetal 

 or embryonal tissues have also been studied. In general, the reactions on 

 the part of very young organisms were definitely diminished in intensity. 

 As far as those of young guinea pigs towards homoiotransplants are con- 

 cerned, this difference is due especially to a diminished intensity of the host 

 connective tissue response towards the graft. The lymphocytic reaction may 

 be quite pronounced, although it may appear at a relatively late date ; this may 

 be due to the fact that the transplant, being less injured by connective tissue, 

 is able to exert a more marked effect on the lymphocytes. We have also re- 

 ferred to the transplantations of heterogenous tumors into the allantois of 

 developing chick embryos, where at early stages the reactions against hetero- 

 differentials are lacking. Similarly, it has been shown by various investigators 

 that the reactions against transplanted tumors may not be so great in newborn 

 animals and in early life as later. Blumenthal has shown that early stages 

 of embryos do not yet contain fully developed organismal differentials. 



It is of interest to compare with these findings the data supplied by sero- 

 logical methods. Roessle immunized rabbits with mammalian and avian em- 

 bryonal tissues and found that these tissues were just as effective as antigens 

 as were red corpuscles of adult animals in the production of hemolysins and 

 also of agglutinins ; there was no difference in this respect between embryonal 

 and adult tissues. On the other hand, injection of pig embryo did not lead 

 to the production of precipitins. The subsequent experiments of Braus also 

 showed that injection of larval and embryonal amphibian tissues into rabbits 

 did not lead to precipitin formation for either foetal or adult tissues, while 

 injection of adult tissue produced precipitins which reacted with adult but not 

 with embryonal tissue. He showed furthermore, that even tissue from an 

 advanced stage of embryonal development which, when serving as host, no 

 longer permitted a heterotransplant to grow, did not yet elicit the production of 

 precipitin. We see, then, that while embryonal tissue may not possess antigen 

 sufficient for precipitin formation, it may possess antigen which is able to 

 call forth the production of hemolysins and agglutinins. Similarly, Uhlenhuth 

 found that while serum of adult chickens gave a positive reaction with anti- 



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