A HUMAN DISPERMIC CHIMAERA FIRST SUSPECTED FROM ANALYSIS OF THE BLOOD GROUP GENE-SPECIFIED GLYCOSYLTRANSFERASES

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Abstract
The red cells of a normal male blood donor were first grouped as B but he lacked anti-A in his serum. Closer investigation revealed that the red cells had very weak A activity, demonstrable only by absorption and elution of anti-A. He is a non-secretor of ABH and a secretor of Lea. Blood group A-, B and H-gene specified glycosyltransferase were detected in the serum. In contrast to the finding of a B antigen of normal strength on red cells, the B transferase in his serum was only about 30% of the normal level and, despite the very weak A activity of the red cells, the A transferase level was about 50% of that found in the serum of group A individuals with normal strength of A antigen. The A transferase on the basis of its pH optimum, KM values for donor and acceptor substrates, activation by divalent cations, isoelectric focusing profile and capacity to convert O to A-active cells, was characterized as the product of an A1 gene. A family study showed that the donor''s wife is group A2 and that they have 2 sons, one group A2 and the other group B. The group B son presumably inherited a B gene from the propositus but the level of B transferase in the son''s serum is 3-times as high as that in his father''s serum. The wife of the propositus and his group A2 son have normal A2 transferases in keeping with their A2 red cell status. The A2 son appears to have inherited an A2 gene from his mother but neither the A1 nor the B gene carried by his father. The distribution of transferase activities in K.S. red cells differs from that in his serum. A level of B transferase within the normal range was found in his red cell membranes but a very low level of A transferase was detected. The discrepancies between the serum transferases and ABO red cell group, together with the inheritance pattern within the family, led to a suspicion of chimerism. This was confirmed by the finding of fibroblasts with the female 46XX karyotype in cultures of the propositus'' skin. Apparently the donor is a dispermic chimera with 2 different cell lines of the genotypes BO and A1O or AaA1. The group A2 son is assumed to have inherited an O gene from his father. The donor''s bone marrow and reproductive organs are probably comprised predominantly of the XY cell line which carries the blood group BO genotype whereas his skin and other tissues, which contribute the A1 transferase to his plasma, are partly made up of the XX cell line which carries the blood group A1O or A1A1 genotype.