Dangers of blood donation between close relatives and couples

Science Q&A

We know that when performing organ or tissue transplants such as bone marrow and kidneys, we often prioritize looking for matches among relatives. However, the situation is just the opposite when it comes to blood transfusion. Close relatives cannot donate blood to each other, otherwise it may cause a serious immune reaction and even cause the death of the recipient. Why is this?

Active lymphocytes become the host

"Blood transfusions between close relatives pose a great safety risk." Wang Chuanxi, deputy director of the Guangzhou Blood Center, said that a serious transfusion reaction called graft-versus-host disease may occur when blood is transfused between immediate family members. This immune response disease has a high mortality rate.

He explained that the transfused blood contained active lymphocytes. Lymphocytes are a type of white blood cell and an important component of the body's immune system. If these active lymphocytes are transfused into an unrelated person, due to the inconsistency of genetic genes, the recipient's own lymphocytes will recognize, reject and kill these "invading" active lymphocytes, so the donor's lymphocytes will not exist in the recipient's body.

However, the genetic genes and tissue structures of immediate family members are very similar. The closer the relationship, the more similar the genetic genes are. In addition, the recipient has low immunity, and his own lymphocytes cannot recognize the transfused active lymphocytes and will regard them as "their own family members." Therefore, foreign active lymphocytes will survive in the recipient's body.

Wang Chuanxi said that although some genetic genes are similar between blood relatives, they are not really "family members" after all. Foreign active lymphocytes will survive and proliferate, and will "turn the tables" and in turn attack the lymphocytes of the recipient and destroy the recipient's tissues and organs. This is graft-versus-host disease.

"Although the incidence of graft-versus-host disease is not high, the mortality rate is relatively high and the treatment effect is relatively poor. It is a very dangerous complication." This immune reaction mainly occurs about one week after blood transfusion, and is manifested by the donor's lymphocytes attacking the recipient's organs and tissues, leading to pancytopenia, severe liver damage, nausea, diarrhea, and large-area rashes or blisters on the skin and mucous membranes.

Wang Chuanxi introduced that there are no accurate statistical data on the incidence of this disease in China, which is estimated to be around one in ten thousand. The probability of blood transfusion between close relatives will greatly increase. The closer the blood relationship, the higher the incidence rate, especially between first-degree relatives, that is, parents and children, the incidence rate is 10-20 times higher.

Blood must be tested before transfusion

In fact, not only are blood transfusions not allowed between close relatives, but in some cases, husbands are also not allowed to give blood transfusions to their wives. This is because, if a wife receives blood from her husband, her body will produce antibodies against his blood type antigens. When the wife is pregnant, the antibodies can reach the fetus, and the fetus may develop hemolytic disease of the newborn. Of course, if there is no consideration of having children, there is no problem for the husband to give blood transfusion to his wife.

At present, some clinical practices adopt the method of component blood transfusion, that is, the freshly drawn blood is processed to separate the various components and then transfused to the patient as needed. For example, an anemic patient only needs red blood cells, but the plasma, white blood cells and other components contained in the freshly collected blood have no therapeutic effect on him, but may very likely cause various adverse reactions to blood transfusion. In this case, only red blood cells are transfused to the patient.

Wang Chuanxi introduced that blood transfusion according to blood components can reduce the occurrence of graft-versus-host disease, and the treatment effect after graft-versus-host disease occurs is relatively good. However, he emphasized that "graft-versus-host disease is not closely related to the blood transfusion components, but is more closely related to whether the blood transfusion and the blood donor are related. As long as there are active lymphocytes in the blood components of the transfused blood, this reaction may occur, because the white blood cells are not removed during the transfusion."

He said that different blood components have different probabilities of causing graft-versus-host disease. "If you only transfuse plasma, there is no such risk, but if you transfuse whole blood or red blood cells, the incidence of graft-versus-host disease is relatively high."

Wang Chuanxi said that misunderstandings about blood transfusions are not uncommon in some reports and TV dramas. In addition to blood transfusions between relatives, there are also cases where when the wounded need blood transfusions and the blood bank is in urgent need of blood transfusions, enthusiastic citizens roll up their sleeves and say "give me my blood". "It is dangerous to transfuse the collected blood to the patient immediately. This is a misunderstanding of blood transfusion by the screenwriter. Blood needs to undergo systematic testing before it can be transfused to the patient. The infection rates of AIDS and hepatitis are relatively high now, and there is a great risk if it is not tested."

These tests include blood type testing and infectious disease source testing, with seven specific items, including three common quality problems of blood type, transaminase, and hemoglobin, as well as virus testing for four infectious diseases (hepatitis B, hepatitis C, AIDS and syphilis). "In addition, there are many infectious diseases that can be transmitted through blood," said Wang Chuanxi.