Frances1 01

Towards meeting the global requirement for safe blood

According to the WHO, an estimated 2 % of the world’s population needs to regularly donate blood to ensure that supply meets demand. Currently approximately 85 million units of red blood cells, the most frequently transfused blood product, are provided per annum globally. Over half the recipients, predominantly in the less developed countries, are children with severe anemia and women suffering from peri-partum hemorrhage. The major problem here is the serious shortage of suitable blood donors: WHO data reveal that in 75 such countries the supply of safe blood is inadequate, leading to medically avoidable maternal and child mortality. In high income countries, however, around 70 % of blood transfusions are given for surgical reasons, particularly to support cardiac, cancer and transplantation patients. Whilst in these countries the blood supply is currently maintained at an adequate level (though the ageing population will inevitably affect this), there is still a small, but crucially not zero, risk associated with blood transfusion.
Donors in the West, however, are carefully screened, and blood is comprehensively tested for transfusion-transmitted infections. Leucocytes, known to harbour infectious agents and to have potentially adverse effects on recipients’ immune systems, are depleted, which can remove 99.995% of the approximately two billion white cells present in a 500 mL unit of blood. Why then is there still a risk? The problem is that stored blood, usually kept for up to five weeks at around 4 °C, deteriorates over time. The residual white cells cause components such as histamine, eosinophil cationic protein and eosinophil protein X to be released into the supernatant fluid, which inhibit neutrophil function and thus impair the immune system of the recipient. Older red cells are also less able to deform and unload oxygen; capillaries can become obstructed leading to tissue ischemia.
As the development of a robust infrastructure for the collection and storage of safe blood in the less developed countries remains an ongoing project, and in the West lowering the storage time for blood is unworkable, is there a solution for the global shortage of safe blood for transfusion? A joint project involving research workers in the UK, Thailand and Japan has demonstrated a feasible approach via the generation of immortalized adult erythroid progenitor cell lines. These allow an unlimited supply of red cells to be produced with minimal culture requirements. In future such technology could not only make transfusion in the West risk-free but might provide a solution for areas of the world with inadequate supplies of safe blood.