Significance of the Research

Researchers and physicians have known for years that there is a difference in immunity between men and women -- but they have not known why. The researchers discovered one possible mechanism driving the difference: The presence of testosterone slows or weakens the response of T-lymphocytes. Delving further to discover the mechanism behind this response, the research team found that without testosterone, the T-lymphocytes "turn-on" more quickly.

It also is possible that other sex hormones play a similar role because testosterone is just one of the hormones known as androgens.

"Females are typically more predisposed to the phenomenon of autoimmunity," says Dr. Kwon. "And of course, what's interesting about this is that females don't have significant levels of testosterone. Men, on the other hand, may have relatively blunted immune responses and have high levels of testosterone. So these results of our experiment are really very promising for unraveling this gender difference in the immune system." He emphasizes that further research is needed to validate these findings before they can be used in human patients in the clinic.

Background Biology

Dr. Kwon frequently cares for patients with prostate cancer. The current experiment grew out of his experience in the clinic. One of the more common forms of treatment for prostate cancer suppresses the patient's testosterone levels to increase the patient's immune attack against cancer. To test the role of testosterone on the immune system in the laboratory, the researchers removed testosterone from male mice.

"They suddenly started growing large numbers of new immune cells," Dr. Kwon says. "We also demonstrated that if you take a male mouse and treat it with chemotherapy you can prompt the mouse to recover its immune system much more quickly simply by remov
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Contact: Bob Nellis
newsbureau@mayo.edu
507-284-5005
Mayo Clinic
5-Nov-2004