Blood is categorized according to antigens into four commonly known types called A, B, AB and O. The Rhesus, or Rh, factor is a kind of protein found on red blood cells. An Rh factor that is either positive, meaning the factor is present, or that is negative, meaning the factor is absent, further classifies a blood type. Negative blood types and negative Rh factors are genetically inherited classifications of antigen expressions on red blood cells.
O Negative
Group O, Rh-negative blood is the most common of the negative blood types. According to the Blood Center of Central Texas, 4 to 8 percent of the American population inherits the O negative blood type. As this type is negative for all of the major group antigens and negative for the Rh factor, it is called the “universal donor." A transfusion of O negative blood causes no reaction in the recipient.
On the other hand, if an O negative patient receives blood from an O positive donor, the positive Rh factor will stimulate the formation of the antibody called anti-D. An O negative pregnant woman who carries an Rh-positive baby may also be exposed to the Rh factor and develop anti-D.
After a patient develops anti-D, any future exposure to the Rh factor will result in a powerful destruction of the Rh-positive blood cells. The antibody attacks the antigen on the positive cells and destroys them.
A Negative
According to the Blood Center of Central Texas, 2 to 7 percent of the American population inherits the A negative blood type. Group A negative patients may receive blood from either group A or group O, Rh-negative donors. Exposure to group B blood or to Rh-positive blood will cause hemolytic antibodies to form that attack the B antigen or the Rh-positive antigen. Exposure can come in the form of a miss-matched transfusion or through a pregnancy.
B Negative
According to the Blood Center of Central Texas, 2 to 4 percent of the American population inherits the B negative blood type. Group B negative patients may receive blood from either group B or group O, Rh-negative donors. Exposure to group A blood or to Rh-positive blood will cause hemolytic antibodies to form that attack the A antigen or the Rh-positive antigen. Exposure can come in the form of a miss-matched transfusion or through a pregnancy.
AB Negative
According to the Blood Center of Central Texas, 1 percent or less of the American population inherits the AB negative blood type. Considered a rare blood type, AB negative patients may receive blood from group AB, group A, group B, and group O, Rh-negative donors. Exposure to the Rh factor during a pregnancy with an Rh-positive baby, or a transfusion of miss-matched Rh-positive blood, will cause the formation of anti-D in the patient.
