A functional analysis was designed to examine the effects of the mutations we identified on the activity and specificity of human A and B transferases. We constructed the expression constructs of A and B transferases and their derivatives in the pSG-5 eukaryotic expression vector. We transfected DNA from those constructs into the human cancer cell line HeLa cells of the uterus. These cell line cells are derived from a type O individual and express H antigens on the cell surface. Therefore, it was expected that if the constructs encode functional A/B transferases, A/B antigens would be produced and expressed on the cell surface. These newly synthesized antigens would then be immunologically detected using anti-A and anti-B antibodies.