The light-colored structures visible in the microscopic image are the web-like structures produced by neutrophils to destroy and trap pathogens. Credit: Julian Hofmann, University of Turku
Researchers have demonstrated for the first time that neutrophils—white blood cells that form part of the body's first line of defense—are found in many tissues during embryonic development, and that they can perform the same functions as adult neutrophils.
The findings warrant further study on the role of embryonic neutrophils in tissue development and in responding to infections in fetuses and newborns.
When inflammation occurs, neutrophils rapidly migrate from the bloodstream into tissues to eliminate harmful microbes. Their role is well understood in adults, but remarkably little when it comes to embryonic neutrophils. During their studies, the researchers from the University of Turku (Finland) discovered there were large populations of neutrophils in several developing embryonic tissues.
The researchers used single-cell RNA sequencing, which revealed that embryonic and adult neutrophils differed slightly in their gene expression, although their major developmental stages proved to be similar.
“Embryonic neutrophils were able to perform immune functions typical to adult neutrophils, such as ingesting particles, producing toxic oxygen compounds, and forming web-like structures that trap pathogens outside the cell,” said study author Julian Hofmann, doctoral researcher from the University of Turku. “Embryonic neutrophils are therefore not merely dormant developing cells, but functionally mature cells.”
One of the most interesting findings of the study is the distribution of neutrophils in developing tissues. As many of the cells are located outside of the blood vessels, they are in direct contact with the developing tissue cells.
“This suggests that embryonic neutrophils may have functions related to tissue development and homeostasis in addition to those related to immune defense,” says Hofmann.
If neutrophils are also found in human tissues during embryonic development, these findings could contribute to future treatments for prenatal and perinatal infections and inflammatory diseases.
Data from University of Turku