Published May 09, 2023 by

Blood Grouping, Donation & Rarest Blood Group

Blood Types

Blood types are classified according to the presence or absence of agglutinogens (antigens) present on the surface of red blood cells, or agglutinins, also called antibodies. Thus, blood are classified into 4 types according to the ABO system into:
Blood Type A: One of the most prevalent kinds, containing anti-B (also known as anti-B) antibodies, may only accept blood from persons with Blood Type A or O;
Blood B: One of the rarest types, includes anti-A (also known as anti-A) antibodies, and may only be transfused by persons of blood types B or O;
AB blood : It is one of the rarest varieties and lacks antibodies to A or B, allowing it to accept any type of blood without experiencing any negative effects;
O blood Group: Sometimes referred to as the universal donor and one of the most prevalent kinds, has anti-A and anti-B antibodies and is only compatible with type O donors; otherwise, agglutination may occur.

Genetic determination of ABO blood types
The presence or absence of agglutinogens in people's blood is determined by the IA, IB or i genes. The IA and IB genes are the most dominant over the i gene. The IA gene, for example, determines the production of an enzyme that synthesizes the A agglutinogen. Therefore, if a person has the IA IA genotype and another person has the IA i genotype, the red blood cells of both have the A agglutinogen, that is , they have blood type A.
Something similar occurs in the case of people with blood type B. But people with type AB have genotype IA IB, as there is no dominance between these two genes. These people are capable of synthesizing both A and B agglutinogens. Finally, a type O person has genotype ii, that is, they do not have the necessary enzymes to manufacture either of the two agglutinogens.

The importance of blood types - transfusions
The discovery by the Austrian physician Karl Landsteiner, in 1900, that there was incompatibility between the blood of certain people, paved the way for the identification of various blood types, including those of the ABO system. Although it is not the only system of blood groups, it is of the greatest practical importance at times of transfusion.

What can happen when a person with type A blood receives type B blood?
Since there are anti-B agglutinins in the receiver's plasma, these substances act as antibodies against the B agglutinogens existing in the donor's red blood cells, causing the rupture of these red blood cells and a reaction known as agglutination reaction. Note that the same reaction will occur if a type A person receives blood from a type AB person.
Type AB people do not have any of the agglutinins of the ABO system and this means that they can receive, by transfusion, blood of any type. Such people are called universal recipients and those with type O blood are universal donors. This means that they can donate blood to anyone, since their red blood cells do not have agglutinogens. Even if the receptor has agglutinins, the agglutinins will have no substance to react against.

The Rh Factor
The ABO system is not the only one to be considered when talking about blood transfusion. There is another important aspect that must be taken into account: the Rh factor, or Rhesus factor. This blood trait was discovered in 1940 by two researchers named Landsteiner and Wiener, who performed experimental blood transfusions on rhesus monkeys.
Basically, the Rh positive occurs when the individual presents a certain antigen on the surface of his red blood cells. People who do not have this characteristic in their blood cells are of the Rh negative type. Unlike the ABO system, in the Rh system, agglutinins do not occur spontaneously. This means that virtually all people are born without anti-Rh agglutinins.
For someone to have anti-Rh antibodies, that individual must be exposed to the Rh antigen. This can occur both by blood transfusion and in conditions of pregnancy, in which the Rh factor is negative in the mother and positive in the fetus. In such cases, anti-Rh agglutinins develop and both the person who received the transfusion and the person who is pregnant become sensitized.
The problem, in both situations, is in the second contact with Rh positive blood. In the case of another blood transfusion, under the same conditions, the recipient's blood may undergo agglutination or his red blood cells may rupture (hemolysis). In relation to pregnancy, if the woman is again giving birth to an Rh positive baby, the mother's anti-Rh agglutinins can cross the placenta, causing agglutination of the fetus' erythrocytes — a disease known as fetal erythroblastosis.
Regarding blood transfusions, people with Rh positive (Rh+) can receive donations of the same Rh and also of Rh negative. Already Rh negative carriers, they can only receive their type, otherwise there will be a risk of blood agglutination and hemolysis.

Compatibility table for blood donation
The following table shows who you can donate blood to and who you can receive it from:

  Blood Types

  Can Donate To

Can Receive
   Blood Type A+

    AB+ and AB-

and O-
   Blood Type A-

A+,A-,AB+ and AB-

A+ and
   Blood Type B+

       B+ and AB+

and O-
   Blood Type B-

  B+,B-,AB+ and AB-

B- and
   Blood Type AB+



   Blood Type AB-

     AB+ and AB-

and O-
   Blood Type O+

A+,B+,AB+ and O+

O+ and
   Blood Type O-



What is your child's blood type?
Usually the child's blood type is identified shortly after birth through the heel prick test. However, the child's blood type can also be identified through routine blood tests or at the request of the child's pediatrician in order to determine the diagnosis of any disease.
In pregnancy, when the mother is Rh negative and the baby is positive, there is a probability that the pregnant woman will produce antibodies to eliminate the baby, which may lead to an abortion. Therefore, pregnant women with this blood type should consult the gynecologist to check when there is an indication of anti-D immunoglobulin injection, but there are never serious problems in a first pregnancy.

Who can donate blood

Blood donation takes an average of 30 minutes and some requirements must be respected, such as:
*Be between 18 and 65 years old, however people aged 16 and over can donate blood as long as they have authorization from parents or guardians and meet the other requirements for donation;
*Weigh more than 50 kg;
*If you have a tattoo, wait between 6 and 12 months to make sure that you have not been infected with any type of hepatitis and that you are still healthy;
*Never have used illicit injectable drugs;
*Wait a year after curing an STI.
Men can only donate blood once every 3 months and a maximum of 4 times a year and women every 4 months and a maximum of 3 times a year, since women lose blood every month through menstruation, taking longer time to replenish the amount of blood withdrawn.
Before donation, it is important to avoid consuming fatty foods at least 4 hours before donation, in addition to avoiding fasting. Therefore, it is recommended to have a light meal before donating blood and after the donation, have a snack afterwards, which is usually provided at the donation site. In addition, it is indicated to drink plenty of fluids, not to smoke for at least 2 hours after the donation and not to perform very intense physical activities, as there may be a risk of fainting, for example.

How to donate blood

The person who wants to donate blood must go to one of the blood collection stations, fill out a form with several questions about their health and lifestyle. The form will be analyzed by an expert and, if the person is able, they can then sit in a comfortable chair for the donation to be made.
A nurse will place a needle in a vein in the arm, through which the blood will flow into a bag designed to store the blood. The donation lasts approximately half an hour and it is possible to ask for leave from work that day, without having your salary deducted.
At the end of the donation, the donor will be offered a reinforced snack to replenish his energy, as it is normal for the donor to feel weak and dizzy, despite the amount of blood withdrawn not reaching half a liter and the body will soon recover this loss .
It is safe to donate blood and the donor does not catch any disease, because he follows national and international blood safety standards from the Ministry of Health, the American Association and the European Council of Blood Banks.

Rarest blood type

There is a blood type so rare that less than 50 people in the world are known to have it. Scientifically known as Rh null (Rhesus null), it is often referred to as “golden blood” because of its extreme rarity — and its value to others.
There are four main blood groups: A, B, AB, and O. This grouping is determined by the presence of A and B antigens that will trigger an immune response if the red blood cell is introduced into someone who is not a match (as in the case of a blood transfusion). Blood type A has A antigens, blood type B has B antigens, blood type AB has both antigens, and blood type O has no antigens either.
In addition to the A and B antigens, there are other proteins found in red blood cells (blood cells) called the Rh factor, the presence or absence of which determines whether a blood type is positive (+) or negative (-). While there are actually 61 blood group antigens (Rh antigens), the negative/positive divide refers to the absence or presence of one in particular—the Rh(D) antigen.
A person can only donate blood to someone with compatible blood antigens. Thus, people with Rh− blood can donate blood to both Rh− and Rh+ recipients, as Rh− lacks the problematic protein. However, those with Rh+ blood cannot donate to Rh− recipients. Rh positive is much more common than Rh negative, although there is some variation between different populations.