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Fresh discoveries about the immune system could eventually help cancer patients who fall ill after receiving a bone marrow transplant. New treatments, claim researchers, could head off the threat of deadly "graft versus host" disease without compromising an immune attack on the cancer.
The immune system's job is to spot foreign tissue and launch an attack.
This allows the body to fight off infections from bacteria and viruses.
However, if a patient has received foreign tissue - such as a new kidney or bone marrow - then these reactions must be suppressed.
New immune system
A bone marrow transplant means that the body is receiving, in effect, the immune system of the donor.
If it does launch an attack, it can be highly dangerous or cause long-lasting symptoms.
The immune cells in the new marrow think the rest of the body is the intruder and attack cells in the gut, skin and liver.
Patients can be given immunosuppressing drugs, which hamper the work of a main attacking immune cell called a t-cell.
However, doctors do not want to completely remove the immune response, as they believe that it can help "mop up" cancer cells left alive after chemotherapy.
Smaller target
The new finding, from doctors at the University of Michigan, could help.
They have found evidence that particular immune system proteins are to blame for launching the attacks on the host's body.
They feel that if these could be blocked, there would be no need for a drug which weakened t-cell response, leaving these cells free to fight the cancer.
The Michigan study identified two "cytokines" - which they feel are key in triggering attacks during graft versus host disease.
These, called tumour necrosis factor alpha, and interleukin-1, could be targeted by drugs, claimed researchers.
Takanori Teshima, a Japan-based scientist involved in the project, said: "Neutralising TNF-alpha and interleukin-1 suppressed dramatically the mortality and mobidity of mice with graft versus host disease."
'Step forward'
Professor Ann Dickinson from Newcastle University is working on tests which may be able to predict whether a child will suffer graft versus host.
She said: "If we could find a means of mopping up these cytokines - and leaving intact cells which could deal with residual leukaemia cells, it would be a step forward.
"Graft versus host is fairly common, though not always severe.
"The most serious cases can be fatal, and even if the patient survives, there can be long-term illness."
[journal Nature Medicine]
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Last Revised at December 10, 2007 by Lusine Kazoyan, M.D.
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