A woman’s immune function changes during pregnancy and after childbirth. However, the immune response also changes during and across the menstrual cycle. I was always intrigued by this because I could ask patients with rheumatoid arthritis about the relationship of their period to the pain and discomfort of their disease and they would always tell me where they were in regard to their menstrual cycle.

Investigators at Indiana University have shown that sexual cycles play a major role in these immune changes, the likes of which are also found in women who are sexually active versus those who are sexually abstinent.

The investigators reported that sexually active women experience greater changes in the proteins that T cells use to communicate, namely cytokines and chemokines from helper T cells. Higher levels of TH1 T cells were also found in these women during what we call the follicular phase of the menstrual cycle, a period when the ovary follicles are maturing (eggs that mother drops to be fertilized by sperm.)

Antibody levels were also different in both groups (sexually active versus sexually inactive) of women. Secretory antibodies, like IgA, are typically found in the mucus of the female reproductive tract and these antibodies are found in the mouth and in the intestine and just about anywhere where there are mucous membranes. Because of this, they can interfere with the movement of sperm and other aspects of fertilization.

Investigators hypothesized that they were really looking at an immune system that was readying the woman’s uterus for the possibility of pregnancy just as a result of sexual activity.

All of this would indicate that the immune system is extremely active in the process of fertilization as well as pregnancy.