| Abstract: | Since the crystallizable fragment (Fc) portion of the immunoglobulin G (IgG) molecule is the binding site of Protein A, a radioimmunoassay procedure using 125I-Protein A was developed for identification of the ABO blood groups. The isotope level bound to Group A, B, or AB red cells decreased with the dilution of anti-A or -B, respectively. After sensitization by anti-A plus B in Group O serum, the isotope bindings were observed in Groups A, B, and AB cells, while no significant radioactive count appeared in Group O cells. Furthermore, there was little significant isotope binding in both Group A and B red cells sensitized by the serum from Group A or B blood containing mainly IgM anti-A or -B. A radioimmunoassay using 125I-Protein A is an excellent method for identifying ABO blood groups. |
