Question: 145: Which of the following reasons in mainly responsible for graft rejection in transplantation of organs?
(1) Inability of recipient to differentiate between ‘self and ‘non-self’ tissues/cells
(2) Humoral immune response only
(3) Auto-immune response
(4) Cell-mediated response
Answer: Option (4)
Explanation:
Graft rejection occurs when the recipient’s immune system recognizes the transplanted organ as non-self.
The major mechanism responsible for graft rejection is the cell-mediated immune response.
T-lymphocytes of the recipient recognize foreign antigens present on the graft cells.
These activated T-cells directly attack the transplanted tissue or release cytokines that lead to destruction of the graft.
Humoral immune response alone is not the primary cause of graft rejection.
Auto-immune response involves attack against self-tissues and is not responsible for graft rejection.
Therefore, graft rejection in organ transplantation is mainly due to cell-mediated immune response.