One surprising aspect of the immune system is that individuals make responses to human tissues from a different individual, causing serious problems for organ and tissue transplantation. The basis for this immune response is:
A) The extensive polymorphism of MHC genes in the human population
B) The fact that transplanted tissues often carry infectious microbes into the recipient
C) The fact that individuals may differ in their blood group antigens (i.e., their blood type)
D) The presence of many antigen-presenting-cells in the transplanted tissue
E) The presence of many B and T lymphocytes in the transplanted tissue

Question

Quizplus · Accepted Answer

The major component of the graft rejection response is due to recognition of the 'foreign' MHC proteins on the graft by the recipient's T lymphocytes. This occurs because of the extensive polymorphism of MHC genes in the human population. As a result, two different individuals nearly always express different MHC molecules from each other. Since MHC molecules are efficiently recognized by T cells, the T cells in the recipient will respond to the donor's tissue and destroy it, just as if it were a pathogen.

One Surprising Aspect of the Immune System Is That Individuals