Certified Histocompatibility Specialist Practice Test 2026 – Your Complete All-in-One Preparation Guide!

After an allogeneic bone marrow transplant, the recipient generally starts to exhibit the HLA typing characteristics of the donor due to the introduction of the donor's hematopoietic stem cells, which will produce new blood cells carrying the donor’s HLA markers.

In this scenario, the expected result after three years would show that the recipient's peripheral blood maintains the HLA-DR type of the donor. The peripheral blood is indicative of the hematopoietic system, which is now populated by the donor’s cells. Therefore, a result showing DR11,12 in the peripheral blood corresponds to the donor's characteristics.

On the other hand, the buccal swab can still show the recipient's original HLA typing, which may not have changed as the buccal cells are derived from the recipient’s epithelial tissues that were not affected by the transplant. This means the buccal swab might still show the original HLA type, such as DR1,11, while the peripheral blood reflects the donor's HLA type.

Thus, the correct answer includes the donor's HLA type in the peripheral blood (DR11,12) and the recipient’s original HLA type in the buccal swab (DR