Donor blood and recipient blood

Donor blood and recipient blood are typed using the red cell surface ABO and Rh systems and screened for antibodies to other cell antigens. “Direct” cross-matching involves directly mixing the patient’s plasma with the donor’s red cells to establish that hemolysis does not occur from any undetected antibodies. An individual’s red cells display A antigen, B antigen, both antigens (AB), or no surface antigens (O). If the patient’s red cells do not display either surface antigen A or surface antigen B, then antibodies will be produced upon exposure to the absent antigen(s). Thus, a person who is type B may develop anti-A antibodies in the serum, and a type O individual may develop circulating anti-A and anti-B antibodies. A type AB individual will not produce antibodies to either A or B antigens and therefore can receive red cells from any donor blood type. People with type O blood display neither A nor B surface antigens and can donate blood cells to any other type (universal red cell donor; Table 36.2). The universal FFP donor, conversely, has type AB blood, which will contain neither anti-A nor anti-B antibodies to antigens on recipient RBCs. Whole blood donors and recipients must be exact ABO matches because whole blood contains both RBCs and serum. For example, a unit of type O whole blood will contain serum with anti-A and anti-B antibodies and therefore cannot be used to transfuse patients who are A, B, or AB blood types.