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Mirococept proteins: extending the life of a kidney transplant Researchers at the MRC Centre for Transplantation at King’s College London have developed a technique that could both significantly extend the duration of a kidney transplant and increase the organ’s condition and shelf life, addressing the pressing demand for donor kidneys. Only about half of transplanted kidneys are still functioning after 10 years inside the patient, around one-third of the time a transplanted kidney should last. Five to 10 per cent of transplants fail within one year. This means that the number of people requiring second transplants greatly increases the overall number of patients on the donor waiting list. As at September 2013, this number was 5,875, however, in 2012/13, only 1,750 kidney transplants took place1. for more than 24 hours. Immune system Mirococept proteins The reason for this failure is the body’s own immune system. When cells of the body meet an ‘intruder’ organism, such as an infection or the cells of a donor organ, part of the immune system — the ‘complement’ system — is activated, which then attacks and attempts to destroy the intruder cells. Ordinarily, to stop the body from attacking its own cells, this system is controlled by ‘regulator’ proteins on the surface of its cells. However, when an organ is removed for transplantation, these regulators are lost from the cell surface due to the lack of blood flow and subsequent lack of oxygen. This means that the complement system will begin to attack the organ’s own cells, severely damaging it. This is part of the reason why organs cannot exist outside of the body This effect is often magnified once the transplant is complete as the complement system supports the recipient’s own blood cells in its attack on the organ, resulting in organ rejection. People who have received a transplant will take drugs to suppress their immune system. However, these will often not completely stop the body from reacting. To address these issues, the MRC team, led by Professor Steve Sacks, has developed a method for coating the inner surface of donor kidneys with a protective layer of Mirococept proteins — an artificial replacement for complement regulators. The application of Mirococept takes just 20 minutes after the kidney is removed from the donor. To ensure adherence of the protein to the kidney, the team have also engineered a ‘tail’, which sticks to the cell membrane2. Kidney transplants The ability of Mirococept to help maintain the Flickr/North Dakota National Guard condition of the organ during transfer would also greatly increase the number of donor organs suitable for transplantation. In early tests, only a fifth of organs worked properly after being stored on ice for 16 hours, compared with more than half of those treated with Mirococept3. This new technique, which has recently started treating patients in the first clinical trial, may drastically reduce the number of people waiting for a second transplant, cutting the overall number of people on the waiting list and potentially saving many lives. End notes http://www.organdonation.nhs.uk/statistics/latest_statistics/index.asp Smith RAG, Koffman G, Chowdhury P, Smith KCG, Watson CJ, Nicholson ML, Zhou WD, Sacks SH. Membrane-localising complement inhibitors - clinical progress. Molecular Immunology, 44 (16), 3915-3915, 2007 3 Patel H, Smith RA, Sacks SH, Zhou W. Therapeutic strategy with a membrane-localizing complement regulator to increase the number of usable donor organs after prolonged cold storage J Am Soc Nephrol. 2006 Apr;17(4):1102-11. Epub 2006 Mar 1 1 2