Cells that can penetrate thick mucus can be useful in delivering drugs to specific parts of the body or fighting infections. However, the dense network of mucus can be challenging for cells to navigate. Now, researchers at the University of Cambridge have discovered how white blood cells manage to zip through the sticky stuff — they wrap themselves in a protective bubble.

The Cambridge team, along with collaborators at the Francis Crick Institute, published their findings in the journal Nature Communications. They focused on neutrophils, a type of white blood cell that forms the first line of defence against infection.

Neutrophils, which make up 50-70% of our circulating white blood cells, play an essential role in the immune system. They are found in large numbers in pus and are important in combating bacterial infections.

Scientists have long been puzzled by how white blood cells manage to move through mucus, which is made up of a complex network of mucins, glycoproteins that give mucus its characteristic sticky properties.

However, the Cambridge researchers found that neutrophils release DNA from their nuclei to form a mesh-like structure that encapsulates the cell, effectively creating a protective coating that prevents mucins from attaching.

The researchers observed that when the neutrophils were exposed to mucus, they would release their DNA within three to five minutes. The DNA would then rapidly form the mesh-like structure that enveloped the cell.

Using time-lapse microscopy, the researchers observed neutrophils moving through mucus at speeds of approximately one cell body length per second. Without the protective DNA mesh, the cells would become stuck in the mucus.

The researchers believe that this mechanism may also help other types of cells to move through mucus, such as cancer cells that metastasize from their original site to other parts of the body.

"This is the first direct evidence that white blood cells secrete DNA to help them move through mucus, and it could explain how various cell types are able to penetrate this dense, protective layer under healthy and diseased conditions," said lead researcher Dr Samuel Henson.

The team say that further studies are needed to investigate the role of this mechanism in other cell types and its potential implications for drug delivery and the treatment of infections.

The findings could also have implications for understanding how cancer cells spread, as some cancers are able to metastasize from their original site to other parts of the body.