What are the blood groups? A, B, AB, 0, Rh positive, Rh

Blood group

In the human body 4 to 6 liters of blood flow. Blood is a liquid tissue composed of plasma and corpuscular elements . Plasma is a liquid formed mainly of water but also containing proteins and nutrients. The corpuscular elements instead are red blood cells , white blood cells and platelets . Red blood cells transport oxygen to the body’s cells and remove carbon dioxide. White blood cells are part of the immune system and help fight infections. Platelets ultimately play an important role in blood clotting.

What is the blood type?

The blood group is a hereditary component and is identified thanks to the antigens present on the surface of red blood cells . Antibodies to antigens absent on an individual’s red blood cells are also present in the blood. There are more than thirty different classification systems.

According to the AB0 (ABzero) system there are four blood groups AB or .

Group A presents antigen A on the surface of red blood cells and anti-B antibodies in the blood.
Group B presents antigen B on red blood cells and anti-A antibodies in the blood.
Group 0 does not present antigens but is characterized by the presence of anti-A and anti-B antibodies in the blood.
Finally, group AB presents antigens A and B on red blood cells, but has no antibodies in the blood.


Each group can be Rh positive or Rh negative , depending on the presence or absence of the Rh D antigen, a protein. According to the AB0 classification therefore each individual will therefore have one of the following blood groups:

  • A Rh D positive (A +)
  • A Rh D negative (A-)
  • B Rh D positive (B +)
  • B Rh D negative (B-)
  • 0 Rh D positive (0+)
  • 0 Rh D negative (0-)
  • AB Rh D positive (AB +)
  • AB Rh D negative (AB-)


What is compatibility between blood groups?

The immune system reacts to the presence of blood that it does not recognize as its own through the production of antibodies that can bind to particular antigens. This reaction can cause agglutination of red blood cells and their destruction.

It is therefore essential that in the case of blood transfusion or organ transplant the blood of the donor and that of the recipient are compatible.


What is the compatibility between blood groups?

Group A can receive blood from group A and group 0.
Group B can receive blood from group B and group 0.
Group AB can receive blood from group A, group B, group AB and group 0.
Group 0 can only receive from group 0.
Patients with Rh + blood can receive Rh + and Rh- blood. Rh-
blood patients can only receive Rh- blood.


A + A +, AB + A +, A-, 0+, 0-
TO- A +, A-, AB +, AB- A-, 0-,
B + B +, B-, AB +, AB- B +, B-, 0+, 0-
B- B +, B-, AB +, AB- B-, 0-
0+ 0+, A +, B +, AB + 0+, 0-
0- All 0-
AB + AB + All
AB- AB +, AB- AB-, A-, B-, 0-

Blood group: donation and nature of antibodies

Generally speaking, it is important to note that a person whose blood belongs to group A develops antibodies that fight group B proteins , while a group B subject has antibodies that react negatively against group A proteins . In the case of group 0 individuals , both A and B blood antibodies are present , with the consequent need to receive blood only from people equipped in the same way as group 0. An individual from group AB instead – who has both antigenic proteins – is not it will make antibodies because if it does it will destroy its own red blood cells.

In summary , the patient can receive:

If it belongs to group A both from donors with group A and 0
If it belongs to group B both from donors with group B and 0
If it belongs to AB and from donors of group A, B, AB and 0
If it belongs to 0 only from donors with group 0.

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