The Warsaw Treaty Organization (also known as the Warsaw Pact) was a political and military alliance established on May 14, 1955 between the Soviet Union and several Eastern European countries.
1 Donors with blood type A... can donate to recipients with blood types A and AB. 2  Donors with blood type B... can donate to recipients with blood types B and AB.  Donors with blood type AB...
A-positive, A-negative, B-positive, B-negative, O-positive, O-negative, AB-positive, AB-negative. (The positive or negative refer to the so-called Rhesus factor). Persons with blood type O are so-called universal donors, since they can give blood to anyone having any of the blood types A, B, O or AB. Persons with blood type AB on the other hand, can give blood only to persons with AB blood type.