Immune System Discovery Offers Hope For Cancer, AIDS Patients

The scientists, led by Associate Professor Richard Boyd and Dr JayneSutherland from the Monash Immunology and Stem Cell Laboratories, haverevitalised the thymus which produces the T cells required to fightinfection but which shuts down from early adulthood.

Their achievement, published in the August issue of the Journalof Immunology, has offered new hope for patients with cancer, AIDS andother immunodeficiencies and for transplant patients.

The Monash study showed inhibiting sex steroids through theLeuteinizing Hormone-Releasing Hormone could help regrow the thymus,increase output of new T cells, enhance T cell responses and improverecovery following bone marrow transplants. It also showed, for thefirst time, that prostate cancer patients who had their sex steroidstemporarily blocked had increased levels of new T cells in their blood.

The researchers found inhibiting sex steroids improved theproduction of haemopoietic stem cells in bone marrow. These cellsprovide 'fuel' for the bone marrow and thymus to produce blood cells.

Associate Professor Boyd said the immune system deterioratedseverely with age, and was further destroyed by severe viral infectionand common cancer treatments such as chemotherapy and radiotherapy.

"The resulting immunodeficiency can allow cancer relapse andleave patients at greater risk of infections which are often fatal," hesaid. "The ability to overcome these immune system deficienciesprovides a completely new approach to treating cancer and may work inmany other severe clinical conditions such as HIV/AIDS. It may alsoboost the effectiveness of vaccines to cancer and infections."

Because the scientists have been able to manipulate the way thethymus grows back, they believe they should be able to rebuild theimmune system of patients who are receiving transplants so donormaterial is not rejected.

The group has initiated pre-clinical trials using thistechnology to induce immune tolerance to organ transplants. The trials,led by clinical immunologist Dr David Sachs, are being undertaken atthe Massachusetts General Hospital, the largest teaching affiliate ofHarvard Medical School.

The technology, licensed to Norwood Immunology, is also aboutto be used in clinical trials in leading US cancer centres on patientsreceiving chemotherapy and haemopoietic stem cell transplants.