Technologies are currently available to produce red blood cells under laboratory conditions; however, the technology is unable to produce red blood cells in sufficient quatrains to provide blood transfusions for patients. This has now changed thanks to developments by the University of Bristol and NHS Blood and Transplant , who have jointly developed a novel method to produce an unlimited supply of red blood cells.The function of blood , as any school text book will remind you, is to transport materials around the body and protects against disease. Blood contains plasma, a liquid that contains dissolved substances, cells and cell fragments. These include: red blood cells, which transport oxygen; white blood cells, which protect against disease; and platelets, which help the blood to clot.Red blood cells are used in blood transfusions. By this blood is donated from another person, or stored by the recipient at an earlier date. Donated blood requires screening to ensure blood group comparability . Blood is often transfused when there is known anemia, active bleeding, or when there is an expectation of serious blood loss. Many national blood transfusion centers face risks of low supply of donated blood.The new method of producing red blood cells on a large scale is based on the current method. The current technique consists of taking a type of stem cell that manufactures red blood cells and stimulating them to do so under laboratory conditions. The weakness here is that each stem cell burns out after a short period of time and can only produce a a limited number of red blood cells. To overcome this, scientists have managed to trap the stem cells at an early stage, which allows them to grow in number indefinitely and provide, theoretically, an unlimited quantity of red blood cells when triggered.While the new process is remarkable it will not replace blood donations for some time; this is because the new method remains very expensive, meaning that the main application will be with producing rarer blood types. With this, one of the researchers called Professor David Anstee told BBC Science : "The first therapeutic use of a cultured red cell product is likely to be for patients with rare blood groups, because suitable conventional red blood cell donations can be difficult to source."The new development has been published in the journal Nature Communications, under the title "An immortalized adult human erythroid line facilitates sustainable and scalable generation of functional red cells."