Ontogeny of Immunological Properties 



561 



present in the extracts. For the larval stages 

 this can be interpreted on the basis of the 

 presence of blood at these stages. For the 

 earlier stages the results mean that, even 

 before blood serum develops, antigens are 

 present that have determinants that are 

 similar to at least some of those of constitu- 

 ents of adult serum. Similar resvilts have been 

 obtained by Flickinger and Nace ('52). 



In order to obtain further information 

 concerning the nature of these antigens 

 Cooper ('48) prepared antisera against frog 

 serum, egg-brei supernatant and egg-yolk 

 platelets. The antiserum against adult serum 

 cross-reacted with saline extracts of the eggs 

 (unfertilized or fertilized), embryos and 

 larvae of various stages, confirming the above- 

 described results. Also the antisera vs. egg 

 "supernatant" and egg "yolk" cross-reacted 

 with adult serum, thereby demonstrating that 

 the egg substances with serum-like reactivity 

 could act as immunizing antigens. In addi- 

 tion the three kinds of antisera (vs. serum, 

 vs. egg "supernatant" and vs. egg "yolk") all 

 reacted with washed, and svxbsequently dis- 

 solved, yolk platelets as well as with a clear 

 solution prepared by high speed centrifuga- 

 tion of the egg "supernatant." The serum- 

 like determinants are, then, evidently present 

 in both the formed elements and the ground 

 substance of the egg. Tests of the antisera 

 with fractions of the frog serum and of clari- 

 fied egg "supernatant" prepared by repeated 

 salting out by 34, 50 and 62 per cent satura- 

 tion with ammonium svilfate gave cross- 

 reactions in all cases. Although these frac- 

 tions are very likely not completely homo- 

 geneous, they may well be sufficiently so to 

 permit the conclusion that determinants of 

 both albumins and globulins of the serum 

 are represented in various substances of the 

 egg. Cooper presents additional evidence, 

 from heat inactivation, that these cross-reac- 

 tive substances of the egg are proteins and 

 suggests also on the basis of the details of 

 the serological reactions that they are not 

 chemically identical with any of the serum 

 proteins. Tests by the Oudin ('48) technique 

 indicated the presence of five to seven such 

 antigens (Cooper, '50). More recently Clay- 

 ton ('53) and Spar ('53) report that some 

 antigens appear and others disappear during 

 gastrulation and neurulation in amphibians. 

 Clayton fvuther reports that ectoderm and 

 archenteric roof contain fractions specific to 

 themselves. 



In chickens Schechtman ('47) has likewise 

 demonstrated the presence of serum-like anti- 

 gens in egg yolk and in extracts of embryos 



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