Progesterone may be why pregnant women are more vulnerable to certain infections

February 28, 2013, Federation of American Societies for Experimental Biology

Women who are pregnant or using synthetic progesterone birth control injections have a conspicuous vulnerability to certain infections including malaria, Listeria, HIV, and herpes simplex virus. A new research report appearing in the March 2013 issue of the Journal of Leukocyte Biology offers strong evidence for a possible explanation: the progesterone receptor, a pregnancy hormone sensor, targets a part of the immune system responsible for protection against these and other invaders. In addition to helping explain why some women are more vulnerable to certain infections, it also sheds light on why some autoimmune diseases, notably rheumatoid arthritis and multiple sclerosis, often go into remission during pregnancy.

"We hope that continued work in this area will ultimately yield better approaches to the prevention of immunological complications of pregnancy, safer and more effective forms of hormonal birth control and novel biological targets for the treatment of autoimmune diseases," said Grant C. Hughes, M.D., a researcher involved in the work from the Division of Rheumatology and Department of Immunology at the University of Washington in Seattle, WA.

To make their discovery, scientists used two groups of mice. The first group had a mutated , or PR gene, which rendered the mice's bodies incapable of sensing progesterone through PR (PR knockout mice). The second group was comprised of normal mice. After various forms of immunization, antibody responses were tracked. When compared to normal mice, PR knockout mice produced much higher , but only in response to forms of immunization requiring T cells, a cell type that normally boosts antibody production by B cells. This prompted a closer look at B and T cells from the PR knockout mice. The researcher saw that when stimulated in the test tube, knockout showed normal, if not slightly less, compared to controls. On the other hand, knockout T cells stimulated in the test tube showed a conspicuous over-production of interferon-gamma, an inflammatory molecule involved in fighting off pregnancy-associated pathogens and in shaping protective antibody responses. Adding progesterone to the test tube blocked interferon-gamma in normal T cells, but not in PR knockout T cells. This suggests that progesterone suppresses interferon gamma in T cells through their PR. To sort out which aspects of the abnormal in PR knockout mice were due to T cells, researchers immunized two groups of normal mice, one transplanted with responder T cells from PR knockout donors, the other with responder T cells from normal donors. Just like in PR , normal mice transplanted with PR knockout responder T cells showed much higher antibody levels than normal mice.

"Pregnancy and hormones have long been known to influence immune responses, but these processes have been poorly understood, said John Wherry, Ph.D., Deputy Editor of the . "This new work is significant for two reasons. First, the identification of progesterone receptors as a mechanism of immune modulation during pregnancy sheds light on the pregnancy-immune phenomenon, and second, these studies define a potentially new target to modulate autoimmunity and immune-mediated problems during pregnancy."

Explore further: Mechanism for esophageal cancer uncovered

More information: Grant C. Hughes, Edward A. Clark, and Alan H. Wong. The intracellular progesterone receptor regulates CD4+ T cells and T cell-dependent antibody responses. J Leukoc Biol March 2013 93:369-375, doi:10.1189/jlb.1012491

Related Stories

Mechanism for esophageal cancer uncovered

April 11, 2011
A gene thought to be associated with cancer development can be a tumor suppressor gene in mice, researchers have discovered. Understanding which genes are involved in spreading cancer could lead to future therapies.

Gingivitis bacteria manipulate your immune system so they can thrive in your gums

January 3, 2013
A new research report published in the Journal of Leukocyte Biology shows how the bacteria known for causing gum disease—Porphyromonas gingivalis—manipulates the body's immune system to disable normal processes that would ...

Recommended for you

Researchers illustrate how muscle growth inhibitor is activated, could aid in treating ALS

January 19, 2018
Researchers at the University of Cincinnati (UC) College of Medicine are part of an international team that has identified how the inactive or latent form of GDF8, a signaling protein also known as myostatin responsible for ...

Bioengineered soft microfibers improve T-cell production

January 18, 2018
T cells play a key role in the body's immune response against pathogens. As a new class of therapeutic approaches, T cells are being harnessed to fight cancer, promising more precise, longer-lasting mitigation than traditional, ...

Weight flux alters molecular profile, study finds

January 17, 2018
The human body undergoes dramatic changes during even short periods of weight gain and loss, according to a study led by researchers at the Stanford University School of Medicine.

Secrets of longevity protein revealed in new study

January 17, 2018
Named after the Greek goddess who spun the thread of life, Klotho proteins play an important role in the regulation of longevity and metabolism. In a recent Yale-led study, researchers revealed the three-dimensional structure ...

The HLF gene protects blood stem cells by maintaining them in a resting state

January 17, 2018
The HLF gene is necessary for maintaining blood stem cells in a resting state, which is crucial for ensuring normal blood production. This has been shown by a new research study from Lund University in Sweden published in ...

Magnetically applied MicroRNAs could one day help relieve constipation

January 17, 2018
Constipation is an underestimated and debilitating medical issue related to the opioid epidemic. As a growing concern, researchers look to new tools to help patients with this side effect of opioid use and aging.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.