Microchimerism in peripheral blood and CD34⁺ cells in a patient (patient 1) 5.1 years after orthotopic liver transplantation as detected by nested SSP-PCR for the HLA-DRB gene.

Donor-specific bands are indicated by an arrow. 14.* and 13.* indicate different DRB subtypes. (A) Control DNA sample of a blood donor with the same HLA-DR type (DR1 and DR2(15) as patient 1 before orthotopic liver transplantation (patient 1's original DNA was no longer available). DR15 and DR16 are both serological splits of DR2, and they have a strong sequence homology. This causes a cross-reactivity in the nested PCR-SSP assay. DR51 is the product of the DRB5 gene, which is in linkage with DR15. (B) DNA mix containing the same sample as in panel A in 1:1 dilution with a DNA sample of a control, who had the same HLA type as patient 1's donor [(DR3(17)and DR6(13)]. The bands with primers 14* and 18 are donor-specific bands derived from sequence homology with DR13 and DR17, respectively. The band at DR52 is the PCR product of the DRB3 gene, which is in linkage with the donor's DR13. (C) DNA from peripheral blood from patient 1 obtained 5.1 years after orthotopic liver transplantation. Recipient-specific bands are 1.1, 15, (16), and 51, whereas donor-specific bands are 17, 13.*, and 52. No other bands are observed. (D) DNA from bone marrow–derived CD34⁺ cells from patient 1. Bands specific for the recipient are 1.1, 15, (16), and 51, whereas donor-specific bands are 17, 13*, and 52. Further bands (7, 8, 12, and 53) may be associated with previous blood transfusions.20