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
Blood ritual The Aztecs believed the gods would provide plentiful crops and healthy long lives as long as blood was ritually given (Pendragon 2). If blood was not sacrificed to the gods, the humans believed they would be punished and endure excessive pain “more violent than any man could ever do” (Pendragon 3). Some Indians practice a political ritual voluntarily where the people donate blood as a way to remember politicians who have died (Copeman 126). The blood donation is literally a donation to people who need transfusions (Copeman 132). The participants donate at donation camps during the birthday or the anniversary