"Panda blood", "dinosaur blood"... How to solve the problem of "blood difficulties" for people with rare blood types

Healthy adults with rare blood types should donate blood, but self-reservation can only be a precautionary measure. Establishing a rare blood type bank is the main way for people with rare blood types to solve the problem of "difficulty in obtaining blood".

Speaking of rare blood types, everyone will think of Rh negative "panda blood". In the hit TV series "Kuaichuang", the blood donated by police officer An Xin to Gao Xiaochen was "panda blood". In real life, there are many rare blood types, even rarer than "panda blood". Recently, the official website of Baoji Central Blood Station in Shaanxi Province announced that the testing staff of Baoji Central Blood Station found a rare ABO subtype - cisAB blood type during routine screening of the blood of an 18-year-old female blood donor.

Rare blood types are mainly inherited

"Panda blood", "dinosaur blood", "golden blood"... From the names, we know that these blood types are precious and rare. "Rare blood type is a rare or uncommon blood type. Different countries have different standards for defining rare blood types." Xie Jinhui, director of the Immunohematology Research Laboratory of Tianjin Blood Center, gave an example. In my country, when a certain blood type phenotype is possessed by less than one in a thousand people in the population, it can be classified as a rare blood type. Finland defines rare blood types as less than two in a thousand people, and France as less than four in a thousand.

Before understanding rare blood types, we must first understand why humans have so many blood types. Xie Jinhui introduced: "People's red blood cells carry different antigens. Some people's red blood cells carry A antigens, some carry B antigens, some have both antigens, and some have neither. Based on this, human blood can be divided into four types: A, B, AB, and O, which is the most common ABO blood type system."

At the same time, there are many antigens in nature that are similar in structure to A and B antigens. When the human immune system comes into contact with these antigens, it will generate corresponding antibodies, so anti-A antibodies and anti-B antibodies often exist naturally in human plasma. During blood transfusion, if blood of different blood types is transfused, a large amount of foreign antigens or antibodies will invade, and red blood cells will rupture due to antibody attacks, resulting in "hemolysis", which can lead to shock, renal failure and even death in severe cases.

However, with the progress of scientific research, scientists have discovered that there are not only two antigens on red blood cells, A and B. The most famous blood type besides ABO blood type is Rh blood type. As of December 2022, the International Society of Blood Transfusion has identified 44 recognized blood type systems, such as P, Kell, Kidd, MNS, Diego, Lewis, Lutheran, Duffy and other blood type systems, which contain 354 red blood cell antigens.

"Blood types are determined by genes, and the formation of rare blood types is also mainly heredity." Xie Jinhui explained that similar to genetic diseases, assuming that the gene that expresses positive Rh antigens is D, and the non-positive gene is d, then DD and Dd are both Rh positive, and dd is Rh negative panda blood. If both parents are Dd, then the offspring is likely to be "panda blood" dd, or it may be a carrier Dd.

Coordinate the construction of rare blood type database

Usually, many tests are conducted before blood transfusion, including ABO blood type test, Rh blood type test, antibody screening, and cross-matching to ensure the safety of blood transfusion. The main purpose of cross-matching is to conduct compatibility testing and simulate the environment in the human body to ensure that there is no immune rejection reaction between the red blood cells and plasma of the donor and recipient.

Xie Jinhui pointed out that the reason why rare blood types are so troublesome is that once antibodies are produced after transfusing blood with different antigens, it is very difficult to find suitable blood. For example, the Rhnull blood type, which is rarer than "panda blood", lacks the antigens of the entire Rh system, which means that people with Rhnull blood type may only have one chance to receive a blood transfusion in their lifetime. Because after the first blood transfusion, an antibody called "anti-Rh29" may be produced in their blood. This antibody will attack red blood cells with Rh antigens, which means it will be difficult to find a blood type that suits them afterwards.

"It is important for everyone to know their blood type." Xie Jinhui reminded that if you find that your blood type is relatively rare, you may face a very difficult situation to find blood sources. For such people, it is recommended that all healthy adults should donate blood in case of emergency.

However, autologous blood storage can only be considered as a precautionary measure. Establishing a rare blood type bank is the main way for people with rare blood types to solve the problem of "difficult blood supply". Blood centers in many provinces and cities have carried out rare blood type screening projects among blood donors, and at the same time, all types of rare blood types and information on rare blood type donors are stored.

"However, the information data of rare blood types are currently managed by each provincial and municipal blood center, and there is no networked sharing of the data." Xie Jinhui said that a networked allocation mechanism for rare blood types should be established so that regional blood transportation can be achieved in emergency situations.