Which of the Following Best Explains Why a Bone Marrow

Which of the following best explains why a bone marrow donor needs to be HLA-matched to the recipient?

A) The bone marrow transplant contains enough mature T cells to reconstitute the recipient and the recipient provides the antigen-presenting cells.
B) The recipient's MHC molecules mediate positive selection of thymocytes in the thymus that interact with donor-derived MHC molecules in the periphery.
C) Reconstituted T cells are restricted by donor,not recipient,HLA allotypes.
D) Without an HLA match,the donor-derived thymocytes undergo negative selection.
E) If the donor is not HLA matched,the reconstituted T cells will be autoreactive.