Though two healthy babies would have been enough for me, my two pregnancies yielded another gift: a break from a blood disorder I’ve been living with for the past decade. As previously discussed here, it’s common for women to experience remission of their autoimmune disease during pregnancy – and now researchers have identified a biological mechanism to explain why.
When studying a small group of pregnant and non-pregnant women, researchers at the University of Michigan and the NIH found the expression of an enzyme known as pyruvate kinase is reduced in immune cells in pregnant women compared to non-pregnant women. And the expression of the enzyme was lower in healthy pregnant women compared to those with preeclampsia, a condition with components similar to autoimmune diseases.
In his search to explain the phenomenon, Petty knew to look for a metabolic pathway or mechanism with two characteristics. It had to “dial down” the intensity of the normal immune response, an action needed so that a pregnant woman does not reject the fetus, which has proteins from the father that are “foreign” to the mother. At the same time, such a mechanism must support cell growth needed by the developing fetus.The activity of the enzyme pyruvate kinase-and and its product, pyruvate-fills both roles…
Petty explains that our normal robust immune response depends upon pyruvate to promote calcium signaling, which, in turn, stimulates the production of messenger molecules called cytokines. When pyruvate is decreased during pregnancy, calcium signaling is also reduced, and the immune response is different than that in non-pregnant individuals. Says Petty, “Modification of signaling along this pathway allows the pregnant woman to maintain an immune response, but at a level that will not harm the fetus.”
The significance extends well beyond exciting me (and perhaps other moms-to-be who’ve experienced the phenomenon). If drugs can be designed to suppress pyruvate kinase activity, they may prove effective at treating a variety of autoimmune disorders. “I have a long list of things I’d like to see developed for the clinic in the next five years,” Petty commented.