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...
1 Type A Negative donors can also provide RBCs for the more scarce Type AB patients if necessary.  Type B Positive/Negative Donors: As the second rarest U.S. blood type, your blood is needed to keep your elite group of Type B patients safe and healthy. Type B Negative donors can also provide RBCs for the more scarce Type AB patients if necessary.