Women's strong immune system

Already early in life, the immune systems of girls and boys differ. For example, girls who are born prematurely have a better survival rate than boys. We also know that estrogen stimulates the immune system, while testosterone inhibits it.

 “Many of the genes involved in the immune system are located on the X chromosome. This means that the immune system in women, who have two X chromosomes and thus more gene variants to choose from, reacts more effectively when fighting certain diseases,” says Camila Consiglio, associate professor at Lund University and head of the Systems Immunology research group at Lund Stem Cell Center.

Better protection from vaccines…

It is the specific immune system, which has learned to recognize infectious agents and produce antibodies, that is stronger in women than in men. Men, whose immune systems are not as combative, are more often affected by cancer. Infectious diseases such as COVID-19, hepatitis, tuberculosis and HIV also cause more serious symptoms in men and with higher mortality. 

"The advantage of more powerful immune system reactions is that women generally have less serious infections and they also have a lower risk of developing cancer," explains Camila Consiglio. "Women also receive higher protection from vaccinations, but at the same time suffer from more side effects, especially during their fertile years."

… but greater risk of autoimmune diseases

The big disadvantage, however, is that the antibodies are also involved in autoimmune diseases. Since women have a strong defense against invaders, the immune cells can sometimes attack their own cells if they perceive them as foreign. Especially after puberty, when estrogen rises in women, the immune system can react with both atopic allergies and autoimmune diseases as a result.

For systemic lupus erythematosus, Sjögren's syndrome and thyroid diseases, 80–90 percent of those who get sick are women. These differences in the immune system are not only found in humans, but also in animals such as lizards, mice, scorpions and some monkeys. Over the course of a lifetime, there are also differences in the immune system in the same person. The sex hormones estrogen and progesterone vary, for example, during the menstrual cycle, which affects the immune response. We also know that the immune system deteriorates with age and that the body's ability to fight inflammation becomes worse over time, which in turn can lead to age-related diseases. 

"By measuring sex hormones during different stages of life, our research group is trying to understand the secrets and changes of the immune system," says Camila.

Understanding differences is key

Camila Consiglio is also studying the immune system in women who have polycystic ovary syndrome, which means they have elevated levels of testosterone. These women are found to have more inflammation and more infections and also became sicker in covid-19, than women without PCOS. At the same time, they also have a higher risk of thyroid diseases. 

"Our immune system is really complex and it is not only affected by hormones, but also by genes and lifestyle," Camila notes. "We hope that in the future we can better understand the differences between men and women, in order to be able to individually adapt vaccine doses and treatments according to gender. Maybe even prevent immune diseases before they develop."

Text and image: Åsa Hansdotter
The article was previously published in the magazine Vetenskap & Hälsa, 2024