The presence or absence of specific antigens (foreign substances that might provoke an immunological response) determines the blood type. There are over 300 antigens, some of which are commonly occurring and some of which are not. A combination of these uncommon and common antigens gives rise to 33 different blood groups or blood types. In this article, we will talk about the 8 main blood types, as well as some of the rarest blood types in the world.
What factors influence blood type?
Genetics determine your blood type. You get a pair of genes from your parents (one from the mother and one from the father) that decide your blood group.
What are the different blood types?
1. The ABO system
Each parent donates one ABO gene to their child. The genes A and B are dominant, while the O gene is recessive. Thus, if you get an O gene from your mother and an A gene from your father, you inherit the A blood type. You also possess the A blood type if you have the AA genotype as a result of inheriting the gene coding for A antigens from both your parents. The inheritance of the B blood type also works in a similar fashion. On the other hand, you may inherit an A gene from one parent and a B gene from the other, resulting in the AB blood type.
To sum it up, the six combinations of these genes are known as genotypes (AA, AB, BB, AO, BO, OO), which give rise to the four blood types, namely, A, B, AB, and O.
2. The Rh factor
The Rh factor is also used to classify blood types. Rh is another antigen that may be discovered on red blood cells. If the cells contain this antigen, they are said to be Rh-positive. On the contrary, they are Rh-negative if they don’t have it. Each blood type is assigned a positive or negative symbol based on whether the Rh antigen is present or not. Thus, taking into account the Rh factor, there are eight different blood types.
Which blood group is the rarest?
AB negative
AB negative is the most uncommon of the eight major blood types. A more detailed split-up of the number of people with the blood group is as follows:
- Caucasian: 1%
- African-American: 0.3%
- Latino-American: 0.2%
- Asian: 0.1%
AB- donors are universal plasma and platelet donors, which means that their plasma and platelets can be given to any patient. Contrary to individuals with AB positive blood group, who are universal recipients, people with AB negative blood type can only receive blood donations from AB negative donors, donors who are O negative as well as individuals with A negative blood type.
Other rare blood types are as follows:
| Blood type | Percentage of people with the blood type |
| B negative | 1.5 per cent |
| B positive | 8.5 per cent |
| O negative | 6.6 per cent |
| A-negative | 6.3 per cent |
Rhnull blood type
Rhnull blood is the most uncommon blood type. This subtype is distinguished by a total absence of Rh antigens. This includes the D antigen as well as 60 other antigens. The blood type is so uncommon that only 43 people have ever been identified with this blood type, and there are only nine donors at present. Individuals with any blood type can accept Rhnull blood. Hence, it is referred to as “golden blood”, as it is worth more than its weight in gold.
Ro blood type
The Ro blood type is a subtype of the Rh-positive blood type. You can have this subtype regardless of whether you have O, A, B or AB blood type. Ro blood is essential in the treatment of sickle cell disease, which is a set of genetic blood abnormalities affecting red blood cells. Due to the disease, the demand for Ro blood type is growing by 10-15% each year, but only 2% of frequent donors have this subtype, making it very rare.
Why do we need to donate the rarest blood types?
People with the gene coding for a specific antigen do not create antibodies against it, but they do produce antibodies against the antigens of a different blood group. For instance, the body of a person with type A blood produces antibodies against the B antigen, but not against the A antigen. Thus, if this individual is given either type B or type AB red blood cells (cells with B antigen), his or her antibodies will attack and kill the foreign cells, resulting in an adverse response. Similarly, a person without the Rh antigen (Rh-negative blood type) will produce antibodies if the Rh antigen (Rh-positive blood type) is introduced into their body. Therefore, it is essential to give an individual the right blood type.
The table below mentions the matching donor blood types for each of the 8 primary blood types.
| Recipient Blood Type | Matching Donor Blood Type |
| A+ | A+, A-, O+, O- |
| A- | A-, O- |
| B+ | B+, B-, O+, O- |
| B- | B-, O- |
| AB+ | Compatible with all blood types |
| AB- | AB-, A-, B-, O- |
| O+ | O+, O- |
| O- | O- |
If a person requires blood transfusions, a blood type that closely matches their own works best. Thus, individuals with a rare blood type can generally, only be transfused with a rare blood type. Thus, it is important for people with rare blood types to donate blood regularly.
Summing It Up
AB negative blood type is one of the rarest in the world. This rare blood type along with the others mentioned in this article are extremely important in hospitals, as they usually have a deficiency of rare blood. Therefore, we at Podium School encourage individuals with these blood types to donate as frequently as possible.
