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The Female Immune System

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Women have more autoimmune disease than men. Two recent reviews showed that we have other immune differences as well. Dr. Trevor L. Gillum of California Baptist University reported several effects of this difference, in addition to the disparity in autoimmune conditions:
1. Females have a lower incidence of multiple organ dysfunction syndrome and sepsis in response to shock.
2. Females have lower incidence of certain types of infection, including bacteria septicemia, pneumonia, influenza, and bacterial meningitis. Females are also less likely to die from these infections.

3. Females have lower rates of atherosclerosis, which is associated with inflammatory processes in the blood vessels.
4. In response to phytohemaglutinin, a toxin used to stimulate cytokine production, females produce more of the Th2 cytokines which are associated with antibodies and autoimmune disease.
5. Males are less likely to die from burns of similar size.

Stress factors, including injury, surgery, trauma, burns, and sepsis, change the immune response for both males and females, in both humans and animal models. Exercise has been studied as a prototype of general stress. “Moderate bouts of exercise have been shown to enhance immunity,” Gillum noted. “However, intense exercise depresses the immune system.”

A possible mechanism is the production of the pro-inflammatory IL-6 cytokine during exercise. The concentration of IL-6 can increase 100-fold after intense exercise. High levels of IL-6 then stimulate the production of anti-inflammatory cytokines. This effect is most pronounced in people who get little exercise. With long-term training, there is less production of inflammatory cytokines during acute periods of exertion.

The phase of the menstrual cycle makes a difference, Gillum noted. Women in the luteal phase produce more inflammatory cytokines in response to intense exercise, compared to women in the follicular phase. Since other types of stress produce similar inflammation, this phenomenon may be related to loss of early pregnancy in conditions of major external stress.

Well-trained athletes show much less sex difference in immune function, according to Dr. Michael Gleeson and colleagues at Loughborough University, UK, and University of the Balearic Islands, Spain. These researchers measured white blood cells and immune cytokines in male and female athletes aged 18 to 35 years. They suggested that the same training load could have a larger immune suppressive effect for women than for men.

Regular exercise is recommended for everyone. It may be especially beneficial for women at risk for autoimmune conditions.


1. Gillum TL et al, “A review of sex differences in immune function after aerobic exercise”, Exerc Immunol Ref. 2011; 17: 104-21. http://www.ncbi.nlm.nih.gov/pubmed/21446354

2. Gleeson M et al, “Sex differences in immune variables and respiratory infection incidence in an athletic population”, Exerc Immunol Ref. 2011; 17: 122-35. http://www.ncbi.nlm.nih.gov/pubmed/21446355

Reviewed June 23, 2011
Edited by Alison Stanton

Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.

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