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
World Blood Donor Day 1868. World Blood Donor Day celebration brings a precious opportunity to all donors for celebrating it on national and global level as well as to commemorate the birthday anniversary of the Karl Landsteiner (a great scientist who won the Nobel Prize for his great discovery of the ABO blood group system). The theme for Blood Donation Day in 2018 is 'Be there for someone else. Give blood. Share life' The theme for Blood Donation Day in 2017 focus on blood donation in emergency situations. The first response when an emergency happens is "What Can You Do?" and the answer is