The scientists, led by Associate Professor Richard Boyd and Dr Jayne Sutherland from the Monash Immunology and Stem Cell Laboratories, have revitalised the thymus which produces the T cells required to fight infection but which shuts down from early adulthood.
Their achievement, published in the August issue of the Journal of Immunology, has offered new hope for patients with cancer, AIDS and other immunodeficiencies and for transplant patients.
The Monash study showed inhibiting sex steroids through the Leuteinizing Hormone-Releasing Hormone could help regrow the thymus, increase output of new T cells, enhance T cell responses and improve recovery following bone marrow transplants. It also showed, for the first time, that prostate cancer patients who had their sex steroids temporarily blocked had increased levels of new T cells in their blood.
The researchers found inhibiting sex steroids improved the production of haemopoietic stem cells in bone marrow. These cells provide 'fuel' for the bone marrow and thymus to produce blood cells.
Associate Professor Boyd said the immune system deteriorated severely with age, and was further destroyed by severe viral infection and common cancer treatments such as chemotherapy and radiotherapy.
"The resulting immunodeficiency can allow cancer relapse and leave patients at greater risk of infections which are often fatal," he said. "The ability to overcome these immune system deficiencies provides a completely new approach to treating cancer and may work in many other severe clinical conditions such as HIV/AIDS. It may also boost the effectiveness of vaccines to cancer and infections."
Because the scientists have been able to manipulate the way the thymus grows back, they believe they should be able to rebuild the immune system of patients who are receiving transplants so donor material is not rejected.
The group has initiated pre-clinical trials using this technology to induce immune tolerance to organ transplants. The trials, led by clinical immunologist Dr David Sachs, are being undertaken at the Massachusetts General Hospital, the largest teaching affiliate of Harvard Medical School.
The technology, licensed to Norwood Immunology, is also about to be used in clinical trials in leading US cancer centres on patients receiving chemotherapy and haemopoietic stem cell transplants.
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Journal
The Journal of Immunology