Assay of alpha-D-galactosyltransferase of subgroup B sera

Carriers of weak B antigen were found in three generations of a family. The red cells of the propositus reacted with anti-A human serum and Dolichos biflorus lectin as strongly as normal A1B red cells, but they agglutinated at 8-fold dilution against anti-B human serum (1:128) and did not have a mixed-field agglutination. The red cells of her niece agglutinated at 32-fold dilution against the same anti-B serum and did not have a mixed-field pattern. Her red cells were provisionally designated B2, analogous to A2 of subgroup A. B antigen of the propositus appeared clearly depressed, and she was provisionally designated A1B2. When papain-treated O red cells were used as acceptors instead of untreated O red cells, group A1B2 sera could convert them into B-active cells, which were agglutinated by anti-B human serum. alpha-D-galactosyltransferase activity in A1B2 serum was about one-eighth that in normal B serum.