Question

Why is that the organs cannot be taken from just anybody? Why is that the doctors check?

Answer 1

Hint: Each individual possesses an immune system that protects the individual from the entry of pathogens or harmful microorganisms that can diseases.

Complete answer:
The immune system of a person is able to differentiate between self and non-self cells due to a cell-mediated immune response. When an individual receives an organ from someone else during transplant surgery, that individual’s immune system may recognize that organ to be foreign. This is because the person's immune system detects that the antigens present on the cells of the organ are different or not "matched."

Mismatched organs, or organs that are not matched closely enough, can lead to blood transfusion reaction or transplant rejection. To ensure such a reaction does not occur, doctors match both the organ donor and the person who is receiving the organ. The more similar the antigens are between the donor and recipient, the less likely that the organ will be rejected. Tissue typing ensures that the organ or tissue is as similar as possible to the tissues of the recipient.

Doctors use immunosuppressants to suppress the recipient's immune system. The goal is to prevent the immune system from attacking the newly transplanted organ when the organ is not closely matched. If these medicines are not used, the body will almost always show an immune response and destroy the foreign tissue. Hence, tissue matching, blood group matching are essential before undertaking any transplant, otherwise, the grafts would be rejected sooner or later.

Note: It is to be noted that there are some exceptions, though. Cornea transplants are rarely rejected because the cornea has no blood supply. Also, transplants from one identical twin to another are almost never rejected.