What are the differences between human blood groups? What blood types are compatible with transfusion?

What are the differences between human blood groups? What blood types are compatible with transfusion? People with which blood group are considered universal donors and recipients?

1) the blood group is determined by the presence or absence of special proteins contained in the plasma (a- and (b-agglutinins) and in erythrocytes (A- and B-agglutinogens); 2) the first blood group is suitable for transfusion to people with any blood group, the second only for people with the second and fourth blood groups, the third blood group is suitable for people with the third and fourth blood groups, and the fourth blood group is used only for people with the fourth blood group; 3) people with the first blood group are universal donors, and those with the fourth blood group are universal recipients.

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