TEMPO.CO, Jakarta - A study shows that women can live longer than men as women's immune system age more slowly. Japanese scientists argue that as the body's defenses weaken over time, men's increased susceptibility to disease shortens their lifespan. The immune system protects the body from infection and cancer, but causes disease when not properly regulated.

Prof Katsuiku Hirokawa of the Tokyo Medical and Dental University and colleagues analyzed blood samples from three-hundred-and-fifty-six healthy men and women aged between twenty and ninety. They measured levels of white blood cells and molecules called cytokines which interact with cells of the immune system to regulate the body's response to disease.

In both sexes, the number of white blood cells per person declined with age. However, closer examination revealed differences between men and women in two key components of the immune system - T-cells, which protect the body from infection, and B-cells, which secrete antibodies.

The rate of decline of most T-cell and B-cell lymphocytes was faster in men, while men also showed a more rapid age-related decline in two cytokines. Two specific types of immune system cell that attack invaders - CD4 T-cells and natural killer cells - increased in number with age, with a higher rate of increase in women than in men.

"Age-related changes in various immunological parameters differ between men and women," Prof Hirokawa said. He added that the decline in immunological parameters in women is slower than that in men.

ISMI WAHID