Elution of group-specific substance A from RBC of various subgroups of A and its effect on the agglutination of AX RBC.

Experiments are described which demonstrate that when the Landsteiner heat elution technique is used to prepare eluates from group A cells, some A substance as well as anti-A is released into the eluates. The concentration found is greatest from A1 RBC and least from Ax, suggesting a relationship with the number of antigen sites on RBC of the various subgroups. Further experiments have shown that the presence of this A-specific substance in eluates accounts for the well-know phenomenon that anti-A from selected group O sera, when eluted from A1 RBC, will not agglutinate Ax even though the original serum showed an appreciable titre against Ax. The presence of the eluted antigen also suggests an explanation for the behaviour of antibody recovered from the red cells of various subgroups of A towards Ax.