Ontogeny of Immunological Properties 



559 



cross-reacting antibodies are removed from 

 an antiserum by precipitation with the heter- 

 ologous antigen. 



It should also be emphasized again that 

 antigens that behave alike serologically are 

 not necessarily identical in over-all chemical 

 constitvition. Similai'ity in serological be- 

 havior can be attributed to identity or close 

 structural resemblance of the so-called de- 

 terminants or combining groups of the anti- 

 gens. For convenience in the following dis- 

 cussion the terms determinants or combining 

 groups will, in general, be omitted, it being 

 understood that when two antigens are desig- 

 nated identical or similar the designation 

 refers primarily to these groups. 



RECENT INVESTIGATIONS ON SALINE 

 EXTRACTS OF EMBRYOS 



The work of various early investigators 

 gave rather inconsistent results concerning 

 the antigens of embryos and adults. Accord- 

 ing to some (e.g., Graham-Smith, '04; Braus, 

 '06; Dunbar, '10; Uhlenhuth et al., '10, '39), 

 embryo and adult seemed to possess no anti- 

 gens in common, whereas others (e.g., Rossle, 

 '05; Kritchewsky, '14, '23; Wilkoewitz and 

 Ziegenspeck, '28) found more or less exten- 

 sive cross-reactions. The divergent results 

 were evidently not due to species differences 

 but were probably largely due to technical 

 difficulties. Much more consistent resvilts 

 have been obtained by the recent investiga- 

 tors in this field. The work of Bm-ke et al. 

 ('44), Cooper ('46, '48, '50), Schechtman 

 ('47, '48, '52), Nace and Schechtman ('48), 

 Perlmann and Gustafson ('48), Maculla 

 ('48a,b), Ebert ('50, '51, '52), Ten Gate and 

 van Doorenmaalen ('50), Flickinger and 

 Nace ('52), Nace ('53), Spar ('53), Clayton 

 ('53), Perlmann ('53), Telfer and Williams 

 ('53) and Telfer ('54) is in agreement in show- 

 ing that eggs, embryos and adixlts possess cer- 

 tain antigens in common. In addition, mainly 

 by means of absorption technique, these work- 

 ers find antigenic differences and have studied 

 to some extent the changes in antigenicity 

 during development. Some of their results are 

 presented here. 



Burke et al. prepared antisera in rabbits 

 against saline extracts of various organs of 

 adult and embryonic chickens. With the ex- 

 ceptions of the lens the extracts of the organs 

 studied (brain, testis, ovary, kidney, liver) 

 showed cross-reactions with the various anti- 

 sera. The cross reactivity of the antisera could 

 be more or less completely removed by 



absorption with heterologous extracts (sedi- 

 mentable constituents obtained after removal 

 of large tissue fragments were used for ab- 

 sorption). When an antiserum against adult 

 brain was thus absorbed and tested with 

 embryo brain extracts, reactions were ob- 

 tained only with embryos of 300 hours (pre- 

 cipitin test) and 260 hours (complement 

 fixation test) of incubation or older. When 

 an antiserum against 312-hour brain was 

 absorbed with heterologous extracts of other 

 312-hour organs, it gave reactions (precipitin 

 tests) with brain extract of embryos of 160 

 hours or older. After absorption of this anti- 

 serum with adult brain extract (sediment) it 

 still reacted with the 160-hour extract. Ac- 

 cording to these experiments, then, antigens 

 of the adult brain first arise at about 260 

 hours. Earlier embryonic brain seems to 

 possess antigens cominon to later stages but 

 not to the adult brain. Somewhat similar 

 results were obtained by Biu'ke et al. on the 

 lens (see Table 22). The antiserum against 

 adult lens proved to be rather organ specific 

 and was, therefore, not absorbed. When 

 tested with lens extracts of embryos of various 

 stages, starting with 72 hours, reactions 

 (complement fixation) were obtained only 

 after 160 hours and reached adult intensity 

 at 330 hours. With a 300-hour lens antiserum 

 reactions were obtained at 120 hours. With 

 a 160-hour antiserum reactions were obtained 

 at 96 hours. Thvis, again, there is indication 

 of antigens disappearing while new ones 

 arise during the development of an organ. 

 From these and similar tests with other or- 

 gans Burke et al. specify the approximate 

 time at which adult organ antigens appear as 

 follows: lens, 146 hours; erythrocytes, 100 

 hours; kidney, 220 hours; brain, testis and 

 ovary, 260 hours. It would appear, then, that 

 adult organ specificity does not arise until 

 a considerable time after the initial morpho- 

 logical differentiation. 



This conclusion of Burke et al. is contra- 

 dicted by the results of Schechtman ('48) 

 and Ebert ('50) indicating the presence of 

 organ (brain, heart, spleen) antigens in the 

 early chick blastoderm, and by the findings 

 of Ten Gate and Van Doorenmaalen ('50), 

 who have detected adult lens antigen in lens 

 vesicles of 60-hour embryos, i.e., before spe- 

 cific morphological differentiation (see Table 

 23). The latter suggest, also, that the ap- 

 parent disappearance of a specific embryonic 

 lens antigen during development (Burke et 

 al.) may be attributed to the presence of 

 yolk in the preparations of embryonic anti- 



