Biology of Humans 4th Edition by Judith Goodenough,Betty McGuire

Exercise 21

Rashon has leukemia, a cancer in which the number of white blood cells increases dramatically. The doctors decide that a bone marrow transfer might help by replacing defective bone stem cells with healthy ones. His girlfriend offered to be a donor, but the doctors chose his brother instead. Why? Why was Rashon given drugs to suppress his immune system after the transplant?