Stripping Down Science by Chris Smith, Dr Christorpher Smith Read Free Book Online Page B

recipient – often a healthy individual who has died following an accident.
    But therein lies the problem. The immune system marshals a highly trained army of white blood cells and antibodies which are programmed to tell friend, known as ‘self’, from foe. So whenever foreign materials are introduced to the body, with the clever exception of a developing foetus, the immune system can detect that the chemical markers or antigens displayed on the surfaces of the cells in foreign tissue do not match those in the rest of the body. When this occurs, the presumed impostor is attacked and destroyed. If this involves a donor organ, it’s termed rejection, a process first described by the French surgeon and Nobel winner Alexis Carrel at the turn of the last century.
    To prevent rejection from occurring, transplant doctors try to genetically match donors and recipients as closely as they can, but there will inevitably be differences between the two and so there is always the prospect of an immune attack. This problem held back the transplant field for many years until the 1970s, when the immune-suppressing drug cyclosporine was discovered. Cyclosporine chemically deafens white bloodcells to the sounds of their own inflammatory signals, which prevents the immune system from mounting its normally well-orchestrated attack and thus protects the donor organ from destruction.
    Sadly, suppressing the immune system in this way comes at a cost, because patients are less able to fight off infections and they are also more prone to malignancies, since the immune system also has a role in killing off cancer cells. Until recently, doctors thought that these side effects were necessary evils and that immunosuppression was vital for the continued survival of a transplanted organ. Now it looks like this might be at least part-myth.
    Indeed, Harvard transplant researcher Megan Sykes and her colleagues 24 have discovered that if a patient undergoing a kidney transplant also simultaneously receives a bone marrow transplant from the same donor, together with a drug to temporarily remove all their white blood cells, they can subsequently stop all immunosuppressive drugs without any signs of rejection. ‘If the bone marrow of two different individuals exists in thesame patient at the same time, the donor bone marrow can re-educate the immune system so it regards tissue from the donor as self,’ says Sykes. ‘We’ve done five patients in a pilot study; four are doing very well. They’ve been off immunosuppression for several years, five years in one case, and their kidneys are being accepted despite the lack of any immunosuppression.’
    Although the researchers aren’t exactly sure yet of the mechanics of the process, they suspect that cells from the donor bone marrow trigger a process called ‘peripheral tolerance’, whereby any of the patient’s own cells that would normally attack the donor organ instead switch themselves off.
    Will the same trick work for other organ transplants? Tests on animals suggest that it certainly can, but at the moment the technique is only suitable for live donor transplants (where a donor gives one of their two healthy kidneys to help a friend or relative). This is because the patient needs to be pre-treated with drugs over a five- to six-day period so that they can receive the bone marrow from the donor.
    Since most transplants involving other organs come from donors who have died, it’s currentlynot possible to keep the organs alive long enough while the patient is prepared. Having said that, a new technique being pioneered by Oxford University researchers Constantin Coussious and Peter Friend can now keep livers alive outside the body using an artificial bloodstream, so it may indeed be only a matter of time …

There was a time when almost every action movie seemed to involve the hero or villain becoming swamped in quicksand, sinking away until only their hat