How many blood types are there?

A blood type or a blood group is a way you can classify red blood cells. The classification is based on antibodies and inherited antigenic substances. Antigens can be glycoproteins, carbohydrates, proteins, and glycolipids. We can also find these antigens in other cells and tissues. Blood types are inherited, which means they are a contribution from both parents. Blood groups are divided into different categories based on the antigens that can be found in red blood cells. There are two main blood types called AB0 and Rh.
 
Blood types weren’t discovered before the 1900s. The first man to discover the difference between blood groups was Karl Landsteiner, who made his discoveries at the University of Vienna. He found out the reason why some blood transfusions weren’t successful, or some of them were even deadly. He made his discoveries by mixing different AB blood groups with the serum of his staff’s blood. From these experiments, he was able to identify three types: A, B, and C. C was later renamed to zero (0) because there are no antigens in this blood cell. A fourth blood group called AB was discovered in 1930. Landsteiner got the Nobel Prize for his discoveries. The chromosomes that determine AB0 blood groups are found on chromosome 9. As already mentioned, there is a second major blood type system called Rh. Rh is a protein that can also be found in red blood cells. You either have Rh protein or you don’t have it. When you have it, it is called RhD positive (or just +), and when you don’t have it, it is called RhD negative (or just -). So all these antigens create the eight most common blood types: A+, A-, B+, B-, and AB+. AB-, 0+, and 0-.
 
When talking about different blood groups, you may also think about blood transfusions. A blood transfusion is a regular medical procedure in which donated blood is given to you through a needle straight into your vein. This procedure is used when people have lost a lot of blood during surgery or have an illness in which their body stops making new blood cells or doesn’t do it correctly. Blood transfusions started in 1795, when Dr. Philip Syng Physick made the first human blood transfusion. Before that, scientists had been experimenting with human and animal blood transfusions. After 1900, when the blood types were discovered, it also made blood transfusions a lot easier. Before receiving a blood transfusion, your blood will be tested to determine your blood type (A, B, AB, or 0) and whether you are Rh positive or Rh negative. The donated blood used for your transfusion must be compatible with your blood type. If it is not the same type of blood, it will clot.
 
Group AB individuals have both A and B antigens on the surface of their red blood cells, and their plasma does not contain any antibodies against either A or B antigen. This means that individuals with type AB blood can receive blood from any blood group, with AB being the most preferable. A Group A individual can only receive blood from individuals with type A or O blood, with A being the most preferable. Group B individuals can only receive blood from individuals with type B or O blood. Group O individuals can only receive blood from another group O individual, but they can donate blood to individuals of any ABO group (A, B, O, or AB).
 
In conclusion, I will bring out some interesting facts about blood types. You may wonder what kinds of blood types are the most common. Here is the information based on the year 2018, type 0+: 35%, 0-: 13%, A+ 30%, A-: 8%, B+: 8%, B-: 2%, AB+: 2%, and AB- 1%. To donate blood, you must be at least 17 years old and weigh over 50 kg. You can donate blood every 56 days. Every year, more than 4.5 million people are saved because of blood transfusions.

https://pixabay.com/el/illustrations/%CE%B1%CE%AF%CE%BC%CE%B1-%CE%B7%CF%80%CE%B1%CF%84%CE%AF%CF%84%CE%B9%CE%B4%CE%B1-%CE%B5%CF%80%CE%B9%CF%83%CF%84%CE%AE%CE%BC%CE%BF%CE%BD%CE%B1%CF%82-%CE%B4%CE%B9%CE%B1%CE%B2%CE%AE%CF%84%CE%B7-4039751/

Sources:
https://en.wikipedia.org/wiki/Blood_type
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3595629/
https://www.blood.co.uk/why-give-blood/blood-types/
https://www.ncbi.nlm.nih.gov/books/NBK499824/
https://www.mayoclinic.org/tests-procedures/blood-transfusion/about/pac-20385168
https://www.memorialcare.org/services/blood-donation/blood-types-and-facts