Immunochemical characterisation of the low-incidence antigen, Dha

Immunoblotting with two examples of anti-Dha to the electrophoretically separated components of antigen-positive membranes gave a positive reaction with a component of the same apparent Mr (40,000) as sialoglycoprotein beta (SGP beta, syn: glycoconnectin, glycophorin C). The Dha antigenic determinant was sensitive to trypsin, but resistant to chymotrypsin and Endo F. By immunoblotting, one anti-Dha failed to react with sialidase-treated Dh(a+) cells, whilst the other gave a positive result. In contrast, neither antibody agglutinated sialidase-treated red cells. SGP beta was precipitated from Dh(a+) and Dh(a-) phenotype red cells by monoclonal anti-beta (NBTS/BRIC 10). SGP beta from Dh(a+) but not from Dh(a-) red cells was stained by immunoblotting with anti-Dha. These results assign the Dha antigenic epitope to SGP beta.