The National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, has awarded nearly US$ 9.7 million over five years to the Radiation Effects Research Foundation (RERF), Japan, to study the effects of atomic bomb radiation and ageing on the human immune system. For the first time, experts in both the United States and Japan will systematically analyse biological samples from the unique population of elderly Japanese atomic bomb survivors to better understand the health consequences of exposure to ionizing radiation on the natural ageing process.

As people grow older, their immune systems also age, leading to a gradual decline in the body's ability to fight infections, respond to vaccinations and prevent the development of cancer. The aging of the immune system, known as immunosenescence, is a major contributing factor to disease and death among the elderly. Radiation exposure appears to accelerate immunosenescence, although the molecular events that cause immunosenescence are not well understood.

According to the World Health Organization, in 2000 there were approximately 600 million people worldwide 60 years and older; WHO estimates that this number will jump to 1.2 billion by 2025 and 2 billion by 2050.

"Understanding how the immune system ages will help us find better ways to care for this growing population," says NIAID director Anthony S Fauci, M.D.

This study will take advantage of the unique cohort of atomic bomb survivors who were exposed to varying levels of radiation in 1945. Using state-of-the-art technology, investigators will analyse blood samples from survivors to determine how radiation exposure alters the normal age-related decline of the immune system and identify the cellular and molecular changes that occur. They also will determine how the observed immune changes are related to disease and infection. One goal is to understand how exposure to ionizing radiation and ageing affect a person's ability to respond to vaccination.

"We will gain valuable information that will benefit not only the general public but also patients undergoing radiation for cancer treatment and those who could be exposed to radiation from an industrial accident or even a terrorist attack," says Daniel Rotrosen, director of NIAI's Division of Allergy, Immunology, and Transplantation, which oversees this award. "This collaboration complements NIAID's programme to develop medical countermeasures against radiological and nuclear threats."

Yoichiro Kosunoki, Kei Nakachi, and Tomonori Hayashi, of the Department of Radiobiology/Molecular Epidemiology at RERF, will lead a team of nine experts in Japan.

RERF, formerly known as the Atomic Bomb Casualty Commission, is a cooperative Japan-US scientific organization that has been in existence for 62 years and is based in Hiroshima and Nagasaki, Japan. The foundation performs research to evaluate and document the long-term health effects of acute radiation exposure on survivors of the atomic bomb.

The NIA leads the federal government effort conducting and supporting research on the biomedical, social and behavioural issues of older people.

NIAID conducts and supports research - at NIH, throughout the United States, and worldwide - to study the causes of infectious and immune-mediated diseases, and to develop better means of preventing, diagnosing and treating these illnesses.