Why Men And Women Differ In Immune Response

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From: " Robynn " <Robynn@...>

Date: Wed Nov 10, 2004 1:28 pm

Subject: Mayo Clinic Discovers One Mechanism For Why Men And Women

Differ In Immune Response

http://www.sciencedaily.com/releases/2004/11/041108015954.htm

Source: Mayo Clinic

Date: 2004-11-10

URL: http://www.sciencedaily.com/releases/2004/11/041108015954.htm

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Mayo Clinic Discovers One Mechanism For Why Men And Women Differ In

Immune Response

ROCHESTER, Minn. - Decreasing testosterone boosts immunity because

testosterone helps control T-lymphocytes, the attack cells of the

immune

system, according to Mayo Clinic-led research in laboratory animals.

The

findings appear in the Nov. 15 edition of the Journal of Immunology

(http://www.jimmunol.org/future/173.10.shtml ).

Collaborators include scientists from Roswell Park Cancer Institute,

Buffalo, N.Y.; the Tumor Immunity and Tolerance Section of the

Laboratory of

Molecular Immunoregulation, National Cancer Institute; and

Medical Institute/Memorial Sloan-Kettering Cancer Center.

" What we are showing is that testosterone seems to impede immunity, "

says

Eugene Kwon, M.D., the Mayo Clinic urologist and immunology researcher

who

led the research team. " However, when testosterone is withdrawn, you

get an

increased host immune response indicated by the rising numbers of

immune

cells that are available to participate. "

T-lymphocytes are cells that are vital to controlling the body's

immune

response. " T cells, " as they are usually called by scientists, are

white

blood cells that can fight against tumor cells and infection.

Alternatively,

T cells can help other immune cells known as " B cells " make antibodies

to

defend the body against certain bacterial and fungal infections, and

possibly against cancer. The research findings may have broad

potential

applications to public health. For example, knowing that testosterone

levels

affect T-cell response may help:

* explain why women are more prone than men to develop " autoimmune

disease. "

* speed the development of drugs that bolster the immune system to

treat

such immune-deficiency diseases as AIDS.

* improve vaccines.

* decrease the time needed to reconstitute the immune system after

bone

marrow transplantation.

* protect cancer patients who are receiving immunotherapy treatments

or who

are vulnerable to infection as a result of chemotherapy.

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 removing androgen. "

When testosterone is removed, the immune cells come back strong and

aggressive, ready to attack. Says Dr. Kwon, " They become twitchy, very

reactive, and in this state they can, in fact, mediate a strong immune

response -- which, as physicians, is just what we want. "

Collaborators and Support

In addition to Dr. Kwon, Mayo Clinic research team members include

Anja C.

Roden, M.D., D. Tri, Mercader, Ph.D., M. Kuntz,

Haidong

Dong, M.D., Ph.D., J. McKean, Ph.D., Esteban Celis, M.D., and

Bradley

C. Leibovich, M.D. Collaborators from other institutions are:

T.

Moser, Roswell Park Cancer Institute; Arthur A. Hurwitz, principal

investigator, Tumor Immunity and Tolerance Section, Laboratory of

Molecular

Immunoregulation, National Cancer Institute; and P. ,

chairman,

Immunology Program, H. Koch Chair in Immunologic Studies,

Attending

Immunologist, Department of Medicine, Investigator,

Medical

Institute, Memorial Sloan-Kettering Cancer Center. The work was

supported by

a National Institutes of Health National Cancer Institute grant; a

U.S.

Department of Defense grant; and the Mayo Foundation.

Editor's Note: The original news release can be found here.

[ http://www.mayoclinic.org/news2004-rst/2499.html ]

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This story has been adapted from a news release issued by Mayo Clinic.

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