ABO blood group system A-type blood, with A2 making up almost all of the rest. These two subgroups are not always interchangeable as far as transfusion is concerned, as some A2 individuals produce antibodies against the A1 antigen. Complications can sometimes arise in rare cases when typing the blood. With the development of DNA sequencing, it has been possible to identify a much larger number of alleles at the ABO locus, each of which can be categorized as A, B, or O in terms of the reaction to transfusion, but which can be distinguished by variations in the DNA sequence. There are six common
Jehovah's Witnesses and blood transfusions was released, outlining Jehovah's Witnesses' general doctrine on blood. In 2000, the Watch Tower Society's stand on blood fractions was clearly stated. Members were instructed to personally decide if accepting a fraction would violate the doctrine on blood. In a later article, members were reminded that Jehovah's Witnesses do not donate blood or store their own blood prior to surgery. In May 2001, the Watch Tower Society revised its medical directives and identity cards addressing its doctrinal position on blood; the revised materials were distributed from May 3, 2001. These revised documents specified that "allogeneic blood transfusions" were unacceptable whereas