Hh blood group final step in the synthesis of the molecule. Depending upon a person's ABO blood type, the H antigen is converted into either the A antigen, B antigen, or both. If a person has group O blood, the H antigen remains unmodified. Therefore, the H antigen is present more in blood type O and less in blood type AB. Two regions of the genome encode two enzymes with very similar substrate specificities: the H locus (FUT1) which encodes the Fucosyl transferase and the Se locus (FUT2) that instead indirectly encodes a soluble form of the H antigen, which is found in
Jehovah's Witnesses and blood transfusions and other blood-borne infections, or immune system reactions. Many physicians have expressed a willingness to respect patients' preferences and provide bloodless treatment and about 200 hospitals offer bloodless medicine and surgery programs for patients who wish to avoid or limit blood transfusions. Bloodless surgery has been successfully performed in significant procedures including open-heart surgery and total hip replacements. A 2012 study in "JAMA Internal Medicine" concluded that "Witnesses do not appear to be at increased risk for surgical complications or long-term mortality when comparisons are properly made by transfusion status. Thus, current extreme blood management strategies do not appear to