The ABO blood grouping of a minute hair sample by the immunohistochemical technique.

The unlabeled antibody (PAP) immunoperoxidase technique was applied to the ABO blood grouping of human scalp hairs. Hair samples were subjected to longitudinal- or cross-sectioning, thus obtaining suitable samples for subsequent immunostaining. The immunostaining was carried out using rabbit anti-A and anti-B sera as the primary antibodies. With this technique, the group-specific staining which is revealed as a dark brown precipitate was clearly observed within the medullae of the hair shaft, and depending on the presence or absence of these precipitates, respective blood groups of unknown hair samples were determined. At the hair root, on the other hand, positive stainings were observed not only in medullary cells but also in some cortical cells of the keratogenous zone. From the present study, it can be safely said that this technique is of practical use for the ABO blood grouping from a minute (less than 3 mm) hair sample.