Transplantation of tissues/organs often fails due to non-acceptance by the patient’s body. Which type of immune response is primarily responsible for such rejections? Choose the best option.

1. Enzyme-mediated immune response
2. Cell-mediated immune response
3. Physical immune response
4. Hormonal immune response

The correct option is B Cell-mediated immune response
Allograft (transplant from a genetically different donor) is the last option for chronic organ failure. Rejection occurs despite tissue typing and blood analysis because of T-lymphocytes ( main effector of cell-mediated immunity). The ability of recipient T-lymphocytes to recognize antigen on the donor organ (non-self) leads to the activation of T-lymphocyte and clonal expansion followed by migration of T-cells into the graft organ which promotes tissue destruction. To minimize graft rejection, patients have to take immunosuppressants lifelong. So, the cell-mediated immune system is primarily responsible for graft rejection.