The antigens of the chick blastula: a comparison between the epiblast, primary hypoblast, yolk entoderm, and extraembryonic yolk by immunoprecipitation in agar.

Antisera to chicken embryo epiblast, primary hypoblast, extraembryonic yolk, and yolk entoderm were elicited in rabbits. Extracts from the different sources were tested for their immunoprecipitation by these antisera in immunoelectrophoresis and double diffusion in agar (Ouchterlony) tests. The main findings were as follows: 1) Antigens recovered in the soluble fractions of the cells of the full hypoblast stage (Eyal-Giladi and Kochav, Stage XIII) are immunologically identical to antigens from the extraembryonic yolk, 2) Similar patterns of precipitation lines were formed between the soluble fractions of both the epiblast and primary hypoblast, and the different antisera. The epiblast and the primary hypoblast differed in 1-2 precipitation lines only, 3) The most prominent antigenic differences between the primary hypoblast and the epiblast reside in the microsomal fraction as revealed by immunoelectrophoresis, and 4) For all four sources of antigens which were compared, it was found that the electrophoretic mobility of the antigens migrating closest to the catodic end is modified according to the ratio of solvent to solute during the preparation of the lyophilized antigen.