APR 05, 2024 11:00 AM PDT

The Hidden Influence of Hormonal Contraception on Immune Cells

WRITTEN BY: Amielle Moreno

Heritable traits and environmental factors influence the immune system in unknown ways. While the systemic immune system has received researchers' attention, little is understood about what variables affect the immune cells residing in the diverse tissues across the body.

The endometrium, a tissue exposed to cycling hormones and a myriad of environmental factors, presented a unique opportunity to explore how heritable and nonheritable factors contribute to immune cell characteristics.

A recent study led by Niklas Björkström at the Karolinska Institutet, published in Science Immunology, examined immune cell diversity in the uterine endometrium.

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Unraveling the Influence of Environment and Genetics

The researchers collected uterine endometrium immune cells from menses and compared them to the peripheral immune cells circulating in the blood.

Contrary to previous assumptions, the researchers found that immune cells residing on the barrier surfaces of the endometrium, such as the skin and mucous membranes, exhibited greater diversity than those found in the bloodstream. The study revealed that this diversity is shaped by environmental factors, challenging traditional views of immune cell uniformity.

The Impact of Hormonal Contraception

One of the study's most striking findings was that of combined oral contraception (COC). While hormonal contraception did not significantly alter the composition of peripheral immune cells in the blood, it had profound effects on immune cells residing in the endometrial tissue.

According to Björkström, "many proinflammatory cytokines were reduced in menses in women on COC (but not systemically) likely reflecting a dampening of the local inflammatory response during menstruation." 

There was a reduction in proinflammatory cytokines, specifically within the endometrial tissue of COC-associated samples. Additionally, the maturation of uterine natural killer (uNK) cells was disrupted in women using COC, indicating a specific effect on immune cell development.

Implications for Immune System Understanding

These findings have implications beyond reproductive health, providing valuable insights into the broader landscape of the immune system. According to the findings, immune cells in some organs are less impacted by genetics than by their environment.

By unraveling the complex interplay between genetics, environment, and hormonal factors, this study opens new avenues for understanding immune system variation and susceptibility.

These findings emphasize the need to account for tissue-specific immune responses in medical interventions and drug development, offering new insights into immune system dynamics.

Sources: Science Immunology, EurkAlert!, Personal Correspondence with Author

About the Author
Doctorate (PhD)
Amielle Moreno earned her doctorate in neuroscience from Emory University and has dedicated her career to science communication, news coverage, and academic writing/editing. She is a published researcher who has branched out to author articles for various science websites. She recently published an original research article detailing her findings on how sensory areas of the brain respond to social sound. When she's not writing or editing, you can find her spinning the latest neuroscience news into comedy gold, hosting her podcast "Miss Behavior Journal Club." This fortnightly humorous podcast features the latest in behavioral research. Her goal in life is to defend and discover scientific truths.
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