Identification of two types of immature antigenic molecules on chicken red cells

Surface-labelled antigen analysis of circulating embryonic erythrocytes shows that the population of 48 000 D antigenic molecules involves an agerelated antigenic complex referred to as E 1 48 K component and, in addition, an antigenic molecule also expressed on immature red cells from anemic adult chickens referred to as Im 48 K component. A second immature antigenic molecular species of 140 000 D was detected on red cells from anemic birds and is referred to as Im 140 K component. The Im 48 K and Im 140 K components have no common determinants, although they are both found on immature red cells of anemic animals. This work suggests that these two immature antigens could be involved in the differentiation process, possibly at different levels of erythroid progenitors.