A specific antibody for cells with acquired B antigen.

An acquired B antigen, present on the red blood cells of a healthy male blood donor, was investigated. An anti-B typing serum which initially detected the weak antigen on the donor cells contained a separable antibody that was specific for cells with the acquired B antigen and did not react with normal group B cells. A similar, specific, immune antibody was produced in a rabbit by the injection of red blood cells with an acquired B antigen.