Group B and AB sera, acting on O red cells in the presence of UDP-galactose,
each converted them into B active cells, which were agglutinated by anti-B human serum
(1:512) at the titer of 128-fold, while group Bm and A(1) Bm sera, converted O red cells
similarly incubated into B active cells, which were agglutinated by anti-B human serum
(1:512) at the titer of 8- to 16-fold. This indicates that α-galactosyltransferase activity in
B(m) and A(1) Bm sera may be about 1/8-1/16 that in B and AB sera. Group CisAB sera, even
after absorption of cold anti-B agglutinins with packed, washed group B red cells, did not
convert O red cells in the presence of UDP-galactose in such a way that they might agglutinate
against anti-B human serum.