The Role of H in the Development of A

Summary. A2 cord bloods do not react with Dolichos bif. anti‐A and their H status is equivalent to that of group O cord bloods, indicating that the A components of these bloods are formed independently of H. Bloods reacting with Dolichos bif. extract require H for the development of their A1 components and this is reflected in the lower H status of these bloods. As the alternative pathway is necessary for the development of the first formed parts of A both the alternative and the orthodox pathways are necessary for the development of bloods with A1 components.