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...
Blood group AB is very rare and although AB blood types are able to receive any type of blood they are not able to donate blood to persons that are not blood group AB. Type O negative blood is considered the universal blood type. People with type O negative blood are called universal donors because type O negative blood is compatible to any blood recipientâs type. Ideally the donorâs blood types should always be an exact match to the recipientâs blood type. Universal donors should only be used in the case of medical emergency where there is an unavailability or shortage of the patientâs blood type or when a blood transfusion needs to be performed immediately, not allowing the time to cross type the blood ...