Langerhan cells reveal differences

Langerhans cells, the immune cells that provide the first line of defence against infection in the epidermal skin, are not genetically identical as was once thought.

Dr Michael Chopin, Dr Stephen Nutt and colleagues from the Walter and Eliza Hall Institute have found that the cells, despite appearing identical, are actually two different types.

“Langerhans cells are produced and found in the skin and are quite unique among immune cells because they do not have a definite life span, they can last for a lifetime,” Nutt said.

“They are only replaced when necessary, such as when the skin is damaged by a burn or a cut. When that happens, new Langerhans cells have to be produced by the bone marrow. These cells look the same, so it was always thought that they were genetically the same and their function was the same. We have shown that this isn’t the case.”

The surprise finding could have repercussions for developing and refining therapies for skin infections and skin cancers.

Although Langerhans cells were discovered nearly 150 years ago, Chopin said there were still a lot of gaps in our knowledge about how they develop and their role in responding to foreign invaders.

Chopin said the research team was initially trying to understand the role of Langerhans cells.

“Not everything that makes contact with the skin is harmful, so it is important the immune system doesn’t overreact,” he said. “We were trying to find out whether Langerhans cells were there to activate an immune response to invaders or to suppress the immune system to prevent it from overreacting.

“While designing the experiment, we found that the genes that define the Langerhans cells that are produced in the skin were different to those of Langerhans cells that came from bone marrow. In essence, we now know that there are two different types of Langerhans cells where we thought there was one. We now need to find out if they behave differently as well.”

Nutt said the research could explain why some promising new drugs have not had the desired effect in the clinic.

“Some clinical trials of drugs that were designed to help boost Langerhans cells in response to infections have not responded as the researchers expected,” Nutt said. “Our finding may help explain why these drugs didn’t work outside the laboratory and our current research may provide guidance in developing therapeutics to treat skin infections or skin cancer.”

The research has been published in the Journal of Experimental Medicine.