Using advanced high-resolution 3D imaging techniques, researchers at the Walter and Eliza Hall Institute of Medical Research in Australia have found a novel population of specialized immune cells that maintain the health of breast ducts.

Breast cancer is the most common cancer in Australian women, resulting in more than 19,000 cases each year, the study noted.

According to the investigators, the cells are called ductal macrophages and function by consuming dying milk-producing cells, which need to be cleared away after milk production stops. Mammary glands evolve throughout life and are of particular interest to breast cancer researchers because the mammary ducts are prone to cancer development.

Most organs have their own population of macrophages, which play important roles in regulating infection, inflammation, and organ function. According to the authors, discovering new mammary duct macrophages could help understand how the immune system interacts with the ductal network and affects mammary gland development.

“As breast cancer researchers, there is a need to understand which cells are doing what, so that we can identify how these intricate cellular processes become dysregulated, such as in the case of breast cancers,” said Jane Visvader, PhD, a researcher on the project, in a statement.

The researchers discovered the new cells while exploring mammary ducts and continued investigating the cells in order to identify their specific role in maintaining healthy breast tissue. The researchers later discovered that no other immune cells were able to carry out this essential process so quickly.

“We were excited to find that these cells play an essential role at a pivotal point in mammary gland function called involution when lactation stops, milk-producing cells die, and breast tissue needs to remodel back to its original state,” said Caleb Dawson, a PhD student and a leader of the preclinical research, in a press release.

There is more research to be done, however, and according to a statement, the team hopes to explore the function of ductal macrophages at various stages of mammary gland development.

“Ductal macrophages are spread throughout the mammary ducts. As cancer grows, these macrophages also increase in number,” Dawson said in the release. “We suspect that there’s the potential for ductal macrophages to inadvertently dampen the body’s immune response, which would have dangerous implications for the growth and spread of cancer in these already prone sites.”

New type of immune cell discovered in breast ducts [news release]. Walter + Eliza Hall Institute of Medical Research; April 28, 2020. Accessed May 7, 2020.