Question

Which of the family members could donate red blood cells for transfusion of any of the four ABO blood types? [2 sentences] (Note that, for the ABO blood group, the serum of blood [the liquid part in which red blood cells are suspended] naturally carries antibodies to the A and B antigens not present on the red cells of that individual's blood. Also note, that for blood transfusions, the donor’s serum is removed so only the red blood cells alone are injected into the recipient’s body].

Answer 1

ABO blood typing or ABO blood grouping is based on the antigens present on the RBC surface .

A blood group - RBC carry A antigen or alpha antigen on their cell surface and anti - B antibodies present in plasma of A blood group . So recipient with A blood group , can not accept blood (RBC) with B antigen as anti - B antibodies will agglutinate the B antigens immediately .

B blood group - RBC carry B antigen or beta antigen on their cell surface and anti - A antibodies present in the plasma of B blood group . So recipient with B blood group can not accept blood (RBC) with A antigen . As anti-A antibodies will agglutinate the A antigens .

AB blood group - RBC carry both A antigen and B antigen on their cell surface. And there is no antibodies in the plasma hence person of this blood group can accept any blood group ( ABO type ) as there is no antibodies to agglutinate any type antigens .

O blood group - RBC does not carry any antigen but carry both anti - A antibodies and anti - B antibodies in plasma, hence person with O blood group can not accept blood ( RBC) with A antigen and B antigen as both the antibodies will agglutinate both kind of antigens .

Therefore,

person with A blood group can accept A and O type blood only . (as o blood gr has no B antigen on RBC ) and can donate blood to person with A and AB blood group only . ( as AB blood does not have anti - A antibodies in plasma )

Person with B blood group can accept B and O type blood only. (as O blood has no A antigen on RBC .) And can donate blood to person with B and AB blood group only . ( as AB blood does not carry any anti - B antibodies)  

Person with AB type blood group can accept any type ( A , B, AB , O ) blood from donor as they have no antibodies in the plasma but they can donate blood only to the person with AB blood group . As the RBC carry both the antigen on their cell surface.

Person with O blood group can accept blood only from O blood group . Due to presence of both antibodies . And can donate to all i.e person with A, B, AB, O type blood ,

Blood group	Can accept	Can donate
A	A, O	A , AB
B	B, O	B, AB
AB	A, B, O, AB	AB
O	O	A, B, AB, O

​​​​​In case of positive blood group has D antigen on RBC surface and no anti-D antibodies in the plasma and negetive blood means there is no D antigen in RBC surface and anti - D antibodies present in the plasma hence person with can accept both positive and negative blood but person with negetive blood can only accept negetive blood as anti - D antibodies will agglutinate the D antigens of RBC of positive blood