Abstract
Appearance and hemagglutination activity of the blood group antigens belonging to four systems in chick embryos and chicks were investigated, using seven inbred strains which were homozygous for the genes determining antigens.
An antigen of the A system was fully expressed at the early embryonic stage. Its agglutinability was relatively high during embryonic development and decreased gradually after hatching. During the third week after hatching, its activity was maintained at the same level as that of adult chickens.
Several antigens of the B and D systems appeared at 7-12th day of incubation. Around this time, the replacement of immature red cells by mature red cells took place. It suggests that these antigens may be not present on immature red cells but present on mature red cells.
An antigen of the R system appeared slowly in the fourth week after hatching. A considerable variation in the time of appearance of the activity among individuals was observed in R antigen of the R system and both M and K antigens of the B system.
