Blood Group Chimeras: A Review

Abstract

More than 70 spontaneous chimeric propositi in man are known. This review attempts to summarize the information given by 32 twin chimeras, 32 dispermic chimeras and 11 chimeras of unestablished type.

DNA Profiles of Chimeric Twins, TS and MR Using the Single-Locus-Probe Technique

“…The proportion of 'foreign' or 'grafted cells' in a chimera varies from case to case. The proportion of 'foreign' cells may very well exceed that of the cells from the germ line [1], or even completely re place the germ line cells in the blood [2].…”

Mosaicism due to myeloid lineage–restricted loss of heterozygosity as cause of spontaneous Rh phenotype splitting

“…In addition, none of the patients displayed congenital or acquired chimerism, 4 as evidenced by microsatellite analysis. This result was remarkable, as spontaneous chimerism had been reported to occur quite frequently.…”

“…2,13,14,51 However, varying proportions of RBC subsets of different phenotypes over time, as also observed in some of the patients of this study, are not an exclusive feature of Rh mosaicism but were also reported for hematopoietic chimerism. 4,5 Moreover, LOH is a major mechanism for inactivation of tumor-suppressor genes, and some of these genes are believed to reside on the short arm of chromosome 1, next to the RH locus. 52 Because of the aforementioned circumstances, it seems generally advisable to perform diagnostic steps to exclude hematologic disease in individuals with spontaneous blood group phenotype splitting.…”

“…4,38 However, all 9 patients denied having a twin, and none had a history of transplantation. Moreover, microsatellite analysis of wholeblood DNA samples (15 different loci located on chromosomes 2-8, 11-13, 16, 18, 19, and 21) ruled out congenital or acquired chimerism in each of the studied patients: exclusively homozygous or well-balanced heterozygous allelic peaks were found, with a maximum of 2 alleles present at each locus (Figure 3).…”

“…Known reasons for such findings include hematopoietic or whole-body chimerism (presence of cells from 2 or more zygotes), mosaicism (presence of cells of different phenotypes derived from one zygote), and somatic RHD mutation. [4][5][6][7] Recently, also mosaicism involving a cell line with uniparental isodisomy for chromosome 1 was described as a reason for ambiguous RhD typing. 8 Many individuals with spontaneous Rh phenotype splitting or progressive Rh antigen loss were found to suffer from hematologic disease, such as acute or chronic myelogenous leukemia, myeloproliferative disease, or myelodysplastic syndrome, in the majority of cases without detectable cytogenetic abnormalities of chromosome 1.…”