There are 29 possible combinations of human blood groups, and for a patient to be given a safe transfusion the right one needs to be available.
Besides the familiar ABO and rhesus systems, science has (after a sticky start, see article) uncovered the MNS system, the Kell system, the Lewis system and the D+ and D- group. Choose wrong—or settle for a less than perfect match because no other is to hand—and antibodies produced by the recipient’s immune system may attack the foreign cells. That can lead to serious consequences.
In the worst cases a patient’s organs may fail and he may die. Several attempts have been made to create artificial blood from chemicals that readily dissolve and transport oxygen, or to process the natural stuff in ways that eliminate the antigenic proteins which provoke this immune response. None, so far, has succeeded. But that has not stopped people trying.
The latest effort, reported in Biomacromolecules by Maryam Tabrizian of McGill University in Montreal and her colleagues, follows the second approach, but with a twist. Instead of purging the antigenic proteins from red blood cells, Dr Tabrizian covers them up.