A Human Dispermic Chimaera First Suspected From Analysis of the Blood Group Gene‐specified Glycosyltransferases

Abstract

Summary The red cells of a normal male blood donor, K.S., were first grouped as B but he was found to lack anti‐A in his serum. Closer investigation revealed that his 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 glycosyltransferases were detected in his serum. In contrast to the finding of a B antigen of normal strength on his red cells, the B transferase in his serum was only about 30% of the normal level and, despite the very weak A activity of K.S.'s 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. Moreover, 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 K.S.'s wife is group A2 and that they have two sons, one group A2 and the other group B. The group B son is assumed to have inherited a B gene from the propositus but the level of B transferase in the son's serum is three 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 therefore appears to have inherited an A2 gene from his mother but neither the A1 nor the B gene shown to be carried by his father. The distribution of transferase activities in K.S.'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 pattern of inheritance within the family, led to a suspicion of chimaerism. This was confirmed by the finding of fibroblasts with the female 46XX karyotype in cultures of the propositus' skin. These results suggest that K.S. is a dispermic chimaera with two different cell lines of the genotypes BO and A1O or A1A1. The group A2 son is assumed to have inherited an O gene from his father. It seems probable that K.S.'s bone marrow and reproductive organs are 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.

Blood Group Chimeras

“…Mr. K. S. (D22) is of particular interest; his very weak A antigen led to a family investigation, and his chimeric state was suggested by the transferase studies [76], The hypothesis that Mr. K. S. might be a chimera was supported by finding that his fibroblasts were XX/XY and that some of his hair roots were chro matin positive.…”

“…Although transferase assays are reported for only a few dispermie chimeras [75], 1 disper mie chimera was ascertained through trans ferase assays. Mr. K. S. reported by Watkins et al [76] appeared to have a very weak A and normal B antigens; however, his serum contained only a weak B transferase but a fairly strong A, transferase. Family studies and karyotyping of fibroblasts confirmed the dispermism suggested by the transferase re sults.…”

“…Mr. K. S. [76] has 100% XY lymphocytes, but 50% of his fibroblasts are XX ; his blood and gonads are dominated by B, but his secretor tissue is largely A{, since his A, transferase is normal and his B transferase low.…”

A dispermic chimerism in a 2-year-old Caucasian boy

“…The two arising different cell lines are randomly distributed in the body. These chimeras are usually detected by sex anomalies [7]; nevertheless, few cases of phenotypically normal male or female dispermic chimeras have been published [3,10,11]. Furthermore, cases of chimerism are described with unknown mechanism of development [9].…”

Chimerism and tetragametic chimerism in humans: implications in autoimmunity, allorecognition and tolerance

“…Examples of chimerism and tetragametism, have been found in mice [58][59][60], and other mammals [61] including humans [62][63][64][65][66]. Affected persons are identified by the production of two populations of cells in all tissues, or/and ambiguous genitalia and hermaphroditism alone or in combination [67].…”