Australasian Science: Australia's authority on science since 1938

Immune Cells Trigger Eczema

By Stephen Luntz

A newly identified type of immune cell in the skin appears to help fight off parasites, but may also be responsible for eczema when it triggers wrongly.

The cells are part of a class known as group 2 innate lymphoid cells (ILC2). The first ILC2 members were discovered 5 years ago in the lungs and gut, with researchers now announcing the discovery of skin equivalents in Nature Immunology.

“Unless you’re looking at the right markers these look a lot like T cells,” says

Dr Ben Roediger of the Centenary Institute. This has allowed them to remain unnoticed despite being quite common.

Roediger identified the cells a few years ago, but his theories on their relationship to other cells turned out to be incorrect. “In late 2010 there was a paper in Nature that described a new type of ILC2 cell in the lungs and fat. We speculated it may be the same as ours and contacted Prof Graham Le Gros of the Malaghan Institute, who confirmed the connection and produced a mouse strain for studying the cells.

“Using these mice, we found that ILC2 cells were the major population in the skin that produced interleukin 13, a molecule that has been linked to a number of allergic diseases, including eczema,” Roediger says. Activation of the cells in the mice produced inflammatory responses, and increased numbers occur in human eczema.

Advanced imaging technologies available at the Centenary Institute have allowed the team to observe the dermal ILC2 cells moving in a distinctive way, with random spurts interrupted by stoppages. “A halt in movement usually indicates some sort of interaction with another cell,” Roediger says. “These cells can squeeze and flow in a manner akin to swimming. They can push through gaps in the skin to get to sites of infection.”

The cells come to a halt when close to mast cells, which fight parasitic infections. Roediger believes the interleukin 5 and 13 produced by his cells affect nearby mast cells, stimulating them to fight invaders.

When triggered inappropriately, however, they contribute to allergies, particularly eczema, by recruiting other cells that produce the reaction.

“This population in particular should make good targets for intervention,” Roediger says. “We should be able to modulate or suppress their reaction without suppressing everything else. In fact it is possible current therapies already affect them.”