Determination of MN blood group from blood stains by electrophoresis and immunoblotting

The determination of blood groups from blood stains is extremely important in medicolegal practice, but there is the possibility of an error in the determination of MN phenotypes by the absorption-elution test. We investigated a new method applying electrophoresis and immunoblotting. As a consequence of various experiments, the most appropriate pretreatment of blood stains was as follows. Blood stains were immersed in physiological saline for 0.5 to 1 h and centrifuged. The supernatant was discarded. The sediment was dissolved in sample buffer (TRIS-buffered physiological saline containing 2% sodium dodecyl sulfate) and followed by thermodegradation. It was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). After transfer to a nitrocellulose membrane by Western blotting, MN phenotypes could be determined accurately from blood stains by an enzyme immunoassay (EIA) using commercially available polyclonal anti-M and anti-N sera. For blood stains more than 1 month old it was not easy to determine the MN phenotypes.