Women's immune systems remain younger for longer
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Researchers looked at the blood of healthy volunteers in Japan, ranging in age between 20 and 90 years old and found that in both sexes the total number of white blood cells per person decreased with age.
The number of neutrophils decreased for both sexes and lymphocytes decreased in men and increased in women. Younger men generally have higher levels of lymphocytes than similarly aged women, so as ageing happens, the number of lymphocytes becomes comparable.
The rate in decline in T cells and B cells was slower for women than men, researchers said.
The study found CD4+ T cells, white blood cells that are an essential part of the human immune system, and NK cells, a type of lymphocyte, increased with age, and the rate of increase was higher in women than men.
Similarly an age-related decline in IL-6 and IL-10 – a group of signaling molecules - was worse in men. There was also an age-dependent decrease in red blood cells for men but not women.
This difference in the ageing of immune systems between men and women is one of many processes which alter as we grow older.
"The process of ageing is different for men and women for many reasons. Women have more oestrogen than men which seems to protect them from cardiovascular disease until menopause," Professor Katsuiku Hirokawa from the Tokyo Medical & Dental University Open Laboratory explained.
"Sex hormones also affect the immune system, especially certain types of lymphocytes. Because people age at different rates a person's immunological parameters could be used to provide an indication of their true biological age," Hirokawa said.
The study was published in BioMed Central's open access journal Immunity & Ageing.