Blood type transfusion can be considered safe as long as the serum of the recipient does not contain antibodies for the blood cell antigens of the donor. The "ABO system" is the most important blood-group system in human-blood transfusion. The associated anti-A and anti-B antibodies are usually "immunoglobulin M", abbreviated IgM, antibodies. ABO IgM antibodies are produced in the first years of life by sensitization to environmental substances such as food, bacteria, and viruses. The original terminology used by Karl Landsteiner in 1901 for the classification was A/B/C; in later publications "C" became "O". Type O is often called "0" ("zero", or
Jehovah's Witnesses and blood transfusions on blood transfusions has come from both members and non-members. A group of dissident Witnesses known as Associated Jehovah's Witnesses for Reform on Blood (AJWRB) states that there is no biblical basis for the prohibition of blood transfusions and seeks to have some policies changed. In a series of articles in the "Journal of Medical Ethics" US neurologist Osamu Muramoto, who is a medical adviser to the AJWRB, has raised issues including what he claims is coercion to refuse transfusions, doctrinal inconsistency, selective use of information by the Watch Tower Society to exaggerate the dangers of transfusions and the use