ABO blood group system and likely predates human migration from Africa. The O01 allele is considered to predate the O02 allele. Some evolutionary biologists theorize that there are four main lineages of the ABO gene and that mutations creating type O have occurred at least three times in humans. From oldest to youngest, these lineages comprise the following alleles: "A101/A201/O09", "B101", "O02" and "O01". The continued presence of the O alleles is hypothesized to be the result of balancing selection. Both theories contradict the previously held theory that type O blood evolved first. It is possible that food and environmental antigens (bacterial, viral, or
Blood transfusion specially tested pediatric blood units that are guaranteed negative for Cytomegalovirus. Most guidelines recommend the provision of CMV-negative blood components and not simply leukoreduced components for newborns or low birthweight infants in whom the immune system is not fully developed. These specific requirements place additional restrictions on blood donors who can donate for neonatal use. vnv Neonatal transfusions typically fall into one of two categories: A "massive transfusion protocol" is used when significant blood loss is present such as in major trauma, when more than ten units of blood are needed. Packed red blood cells, fresh frozen plasma, and platelets