Tetraparental sheep chimaeras induced by blastomere transplantation. Changes in blood type with age.

The blood groups are described of three sheep chimaeras produced by injection of blastomere cells into fertilized eggs of different parental origin. Evidence is presented that these chimaeras had a blood type which could only have been derived from both sets of parental genes. Two antigenically distinct red cell populations were identified in all three sheep and chimaerism of serum transferrin and albumin types was also present in two of them. One sheep had a mixture of red cell potassium types and another of haemoglobin types. Soluble R and O blood group substances were present together in the saliva of all three sheep and on the red cells of two of them. The relative proportions of the two red cell populations changed with age of the sheep, the blastomere-derived population becoming less. In one sheep one transferrin type also declined. A fourth sheep studied was not a blood chimaera but was apparently composed of blood derived entirely from that of the transplanted blastomere cells. All four sheep were phenotypically male but studies of cultured leucocytes showed that female cells were present in two of the chimaeras (34 per cent and 89 per cent respectively).