Some Immune System Cells May Play Role In Heart Development, Claims Study

Some cells part of the immune system may help guide the early development of the heart, and play a role in how the organ beats in adults, according to a study that may lead to novel drug targets for heart diseases. The research, published in the journal JCI Insight noted that B cells, a type of immune cells that circulate in the bloodstream and aid in fighting off infection, are present in the small blood vessels that feed oxygen and nutrients to the heart muscle.

According to the scientists, including those from the Washington University School of Medicine in the US, these circulating B cells arrive in the heart vasculature and become sticky. "This behaviour of the immune system B cells has not been described before," said study co-author Luigi Adamo from the Washington University School of Medicine.

"There appears to be some type of interaction between these B cells and the inner lining of the heart's blood vessels. Our study sets the stage to start developing B cell-targeted therapies for various forms of heart disease," Adamo said in a statement. The sticky B cells, they said, slow down considerably in the blood vessels, taking their time as they transit through the heart vasculature. "We're still working to understand why," Adamo said.

"But what was even more surprising was what happened when we removed B cells from the mice," he added. When the scientists assessed genetically modified mice that lacked B cells, they found that their hearts were smaller, and contracted differently than those of normal mice. According to the study, the hearts of mice lacking the B cells relaxed faster and pushed more blood out of the left ventricle with each beat.

The scientists said that in such mice, the number of T cells -- a different type of immune cell -- doubled in the heart. "We are working on more studies to learn if the missing B cells have a direct effect on the structure and rhythm of the heart, or if we are seeing some indirect effect during development or through the change in T cells," Adamo said.

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"But that removing B cells had any effect on the heart is completely unexpected," he added. The researchers speculated that this type of slowly travelling B cell is present and has an effect on other organs as well.

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