Postpartum depression is a serious problem that affects one in seven new mothers and has a negative impact on the mental health of both the mother and her baby, but until now it has not been possible to find out what the biological mechanisms involved in this are disorder. Now new research has analyzed the biological differences in women with this type of depression and has found relevant changes in their B cells.
B cells are part of the immune system and are activated when their receptor recognizes an antigen and binds to it to produce antibodies that defend us against invading pathogens that cause disease. These cells are also responsible for secreting pro-inflammatory and anti-inflammatory factors. The study has been carried out by researchers from the UNC School of Medicine (United States) and has been published in Molecular Psychiatry.
These researchers are the first to look at multiple levels of biology in women with postpartum depression (PPD) – the largest association study of PPD in the entire transcriptome to date – to identify differences between mothers with the disorder and those that don’t. Jerry Guintivano, assistant professor in the UNC Department of Psychiatry and director of the study, said, “Much of the biological research is focused on candidate genes and hormones, and we have a lead on some specific drugs for postpartum depression, but it is important to take multiple avenues to address this condition. Not all manifestations of postpartum depression are the same.
The difficult balance of the immune system during pregnancy
To carry out the research, blood samples were obtained from 1,500 women of different races and ethnicities in North Carolina who had given birth in the last six weeks. Of all of them, 482 were diagnosed with postpartum depression. The researchers used RNA sequencing, DNA genotyping, and DNA methylation assessment to look for differences in components of blood samples from women with PPD and women without PPD.
During pregnancy the immune system “has to prevent infection from a cold, and it also has to fine-tune itself so as not to recognize the fetus as a foreign body and attack it.”
“There is a really delicate interaction of the immune system during pregnancy,” Guintivano explained: “It has to prevent infection from a cold, and it also has to fine-tune itself so that it doesn’t recognize the fetus as a foreign body and attack it. Then, in the postpartum period, all of these hormones and pathways reset to the pre-pregnancy state.”
The researchers found thousands of individual B-cell transcripts that were different in women with postpartum depression from women without the disorder, and that were in part regulated by genetic variants and DNA methylation. To confirm these results, they performed an analysis of the pathway, which involved altered B-cell activation and insulin resistance.
“This is really just the first step in a long line of research that now needs to be done,” Guintivano said. “This is the largest study of its kind, but we still don’t know why the B cells are changing. Do they reflect another change in the body that is caused by postpartum depression or what causes it? What is driving this B cell behavior? The researchers’ next goal, according to Guintivano, will be to conduct a longitudinal study that monitors women for longer to observe how B cells change during pregnancy and postpartum.
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