On the Rare ayr Phenotype of Hepatitis B Antigen

We describe an example of the rare, recently identified ayr phenotype of hepatitis B antigen, detected in the serum of a carrier in New Guinea. All three determinants were apparently present together on the same antigenic particle; but whereas the a and the y reacted as expected, the behavior of the r, in this particular case, was unusual. Taking into account the close association of the ayr phenotype with the Far Eastern ‘r zone’, we suggest three possible mechanisms which may explain its origin and significance.