A study published online in the journal Nature suggests it might be possible to develop vaccines to prevent premature birth and other pregnancy complications.

If so, such vaccines would be the first intended to suppress the immune response rather than activating it.

The study, led by Sing Sing Way, MD, PhD, a researcher in Infectious Diseases at Cincinnati Children’s, shows that the immune system of a pregnant mother stimulates regulatory T cells that prevent attack and rejection of fetal tissues. Importantly, these pregnancy-induced cells are retained after delivery, and rapidly re-accumulate to provide protection in subsequent pregnancies.

Successful pregnancy requires the ability to tolerate foreign antigens inherited from the father.  The mother’s immune response produces regulatory T cells that recognize the fetal antigens. If the mother gets pregnant again, these T cells remember the first pregnancy and provide additional protection to the fetus from being attacked by the mother’s own immune system.

“We show definitively that immune suppressive regulatory CD4 cells can form immunological memory,” says Way, the study’s senior author.  “These memory features shown in pregnancy illustrate why complications become reduced in subsequent pregnancies compared with primary pregnancy.”

These findings can be broadly applied to new ways to prevent autoimmune diseases – such as juvenile idiopathic arthritis (JIA) and type 1 diabetes –by controlling the balance between immune stimulation and suppression.

“Knowing this, we can design vaccines that specifically target immune suppressive T cells,” Way explains. “Current vaccines exclusively target immune activating T cells. With the polio vaccine, for example, vaccination is designed to induce long-lasting immune-activating cells that eradicate the virus with later infection. A vaccine that targets the expansion and retention of immune suppressive cells would allow selective silencing of undesired responses and prevent them from attacking the body.”

Way conducted the study in mouse models of pregnancy with colleagues from the University of Minnesota School of Medicine. The research was supported by the National Institute of Allergy and Infectious Diseases (NIAID) and the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).