Distribution of Antigens in the Developing Newt Embryo

T H E mechanism of differentiation presents one of the central problems of embryology, and it seems reasonable to assume that the development of tissue and organ specificities, in a chemical sense, mirrors differentiation as recognized by the classical methods of embryonic grafting and histological analysis. It is now well established that it is possible, by means of immunological techniques, to demonstrate certain specificities among the organs of adult animals, that is, that organ-specific antigens exist. Conversely, cross-reactions between a number of organ extracts and the antiserum to one organ indicate identity or similarity of some of their antigens (for bibliography see Landsteiner, 1945). The ontogeny of organ antigenic specificity is therefore of interest to the embryologist. The earlier work has been reviewed by Needham (1942) and Cooper (1946). ' In more recent work, using refined techniques, a number of antigens similar to or identical with adult/ antigens have been demonstrated in the embryo. Some of these have been shown to be first detectable at definite stages in embryonic development. The antigenic composition of particular embryonic organs has been analysed by means of antisera to corresponding adult organs. Differences in antigenic composition between embryonic organs have been indicated which may not correspond to those existing between their adult counterparts. Finally a number of antigens have been shown to be characteristic of the embryo or foetus only, being absent in the adult. } The present author is not aware of any attempt to analyse the spatial distribution of antigens in an embryo before the stage of organogenesis. An attempt has been made, therefore, to investigate the earliest stages of morphogenesis in an embryo whose dissection might prove relatively easy and large numbers of which were available. The embryo of Triturus alpestris was accordingly chosen for this purpose.