Figure 8.11: ABO Blood Groups Are Important in Transfusions The table shows the results of mixing red blood cells of types A, B, AB, and O with serum containing anti-A or anti-B antibodies. As you look down the two columns on the right, note that each of the types, when mixed separately with anti-A and with anti-B, gives a unique pair of results. This is the basic method by which blood is typed.