344 IMMUNOLOGICAL STUDIES 



used in this discussion primarily with reference to the determi- 

 nant groups. 



If extracts of various tissues and organs of the adult contained 

 solely or primarily antigens characteristic of the tissue or organ, 

 problems of detection of these antigens in the developing embryo 

 could be rather directly approached. Examples of such organ- 

 specific preparations can be found in the immunological litera- 

 ture, but they are not as numerous or clear-cut as might be de- 

 sired. The classical example is that of lens protein, first described 

 many years ago by Uhlenhuth ( 1903 ) . Antisera against saline- 

 soluble proteins of the lens of the vertebrate eye do not cross- 

 react with other proteins of the same organism. On the other 

 hand, they are largely lacking in species specificity since they 

 cross-react quite generally with lens extracts from various verte- 

 brates from fish to man. Alcoholic extracts of vertebrate brain 

 have also been shown to possess such organ-specific antigenicity 

 although in this case there are cross reactions with testis (see 

 Witebsky, 1929; Lewis, 1933). Another example is thyroglobulin, 

 recently studied by Witebsky et at. (1955). References to other 

 work on this subject may be found in various texts such as those 

 of Landsteiner (1947), Loeb (1945), and Raffel (1953). In most 

 cases the antibodies against various organ or tissue extracts show 

 rather broad cross reactivity. Selective absorption procedures 

 must therefore generally be used to demonstrate distinct anti- 

 genic constituents in various organs, but this suffers from tech- 

 nical limitations when most of the antibodies in an antiserum 

 against a particular preparation are directed against antigens 

 common to various tissues and organs. 



Relation of Embryonic to Adult Antigens 



At one time it was thought that eggs and developing embryos 

 possessed no antigens similar to those of the adult, or even that 

 their proteins were of such "general" nature as to lack antigenic 

 properties. The work of many recent investigators has abundantly 

 demonstrated in many species of animals that the eggs and devel- 

 oping embryos possess antigenically active materials, that many 

 of the antigens are similar to certain adult antigens, and that 



