Blood can be grouped by using two groupings ABO grouping, Rh grouping.
ABO Grouping
Antigens are present on the surface of the RBCs .Therefore, ABO grouping depends on the presence of type of antigen on the RBCs, and namely antigens are only A, B. So blood groups are A, B, AB, and O.
A blood group have only A antigens on the surface of the RBC and B blood group have only B antigens on the surface of the RBCs . Since AB blood group have both A and B antigens on the surface of the RBCs and O blood group have no antigens on the surface of RBCs. Therefore, there are only two type of antigens.
Antibodies are the proteins present in the plasma in response to antigens .There are also A and B antibodies only. A blood group have B antibody in plasma and B blood group have only A antibody in plasma. Since AB blood group have no antibody in plasma and O blood group have both A and B antibodies in plasma. Therefore, there are only two types of antibodies.
Blood Transfusion
Donor is the person who gives his blood to recipient. Whereas recipient is a person who takes blood from donor . the transfer of blood from donor to recipient is called as blood transfusion.
Image source
https://www.pmfias.com/wp-content/uploads/2016/03/Blood-Groups-ABO-Grouping.jpg
From above image we can understand that A Blood group can take blood from O and A blood group donors only. B Blood group can take blood from O and B blood group donors only. AB Blood group can take blood from O and AB, A ,B blood group donors . O Blood group can take blood from O blood group donors only.
From above you can see O can give blood to the recipients of every blood groups so it is called as Universal Donor. AB can take blood from all the donors of every blood groups so it is called as Universal Recipient.
Note: if wrong transfusion of blood will be done then antibodies will be produced which will lead to clumping of blood ,it can even lead to death.
Rh grouping
Other type of the antigen which was first found in Rhesus monkey , are also present on the surface of the RBCs of the human beings. there are two types of antigens Rh +ve , Rh -ve. So blood groups are always assisted by +ve,-ve. Check your blood group only, suppose it is O+, A- . Similarly if there would be wrong transfusion then antibodies will be produced, it can lead to death also.
During pregnancy
If the Rh+ve mother carries Rh-ve child then the first delivery will be normal but antibodies will be formed for Rh –ve antigens, but second time if she carries again Rh –ve child ,because the antibodies produced during first pregnancy will destroy the foetus RBCs. And the child will die. But if because of medical treatment the baby takes birth he would be anaemic or would have jaundice .this disease is also called as erythroblastosis fetalis.
