Explain why a boy with leukemia who receives a bone marrow transplant from his sister that is perfectly matched for MHC class I and class II is still likely to get graft-versus-host disease

Question

What will be an ideal response?

Answer 1

Graft-versus-host disease is caused by T cells in the transplanted bone marrow making an immune response against antigens on the recipient's tissues. This can happen even though donor and recipient are HLA matched, because there are proteins other than HLA antigens that can differ between people and provoke an immune response. Such antigens are known as minor histocompatibility antigens. In a bone marrow transplant from a female to a male, the minor histocompatibility antigens most likely to cause a problem are male-specific proteins (which are encoded on the Y chromosome) that a female's T cells will not be tolerant to and will see as ‘foreign' or non-self.