Abstract
The effect of pH on color development was examined in detail to detect higher sensitivity of ABO blood groups substances in saliva and semen by means of an indirect enzyme-linked immunosorbent assay (ELISA) using secondly antibody conjugated with horseradish peroxidase. The use of McIlvaine buffer was the most effective for color development. Deep color was observed at pH 5.0, and intensity was about 32 times stronger than that obtained with the Tris-HCl buffer (pH 7.6) that was widely used in the Japanese Criminal Investigation Laboratories. Owing to the increased sensitivity, B-type and O-type blood of non-secretors semen, which could not be detected by ELISA, were successfully determined under the present conditions. Through this study, we found the interesting fact that commercially available monoclonal antibodies can be divided into two groups: One group reacts with secretor sample alone and the other reacts with both secretor and non-secretor samples. Using these two classified antibodies, we were able to discriminate between secretor and non-secretor and to speculate the blood type of one sample from two mixed samples.
