How stress can stop immune cells in their tracks

How stress can stop immune cells in their tracks: Researchers have discovered that signals produced by nerves in response to stress can stop immune cells from effectively fighting pathogens or tumours.

Led by University of Melbourne Professor Scott Mueller, Laboratory Head at the Peter Doherty Institute for Infection and Immunity (Doherty Institute), the study made the striking observation that in response to a period of stress, immune cells ceased moving.

While this isn’t permanent, stress can dramatically affect the way our immune system responds.

Published today in Immunity, Professor Mueller and his team used an advanced imaging technique known as intravital microscopy to look at how stress impacts cells of the immune system of mice in real time.

Intravital microscopy uses a special technique to image cells of a live animal in real-time. The intravital microscopy technique which allowed the researchers to watch this phenomenon is very difficult to do in people as it requires body tissue.

“We know anecdotally that when we are stressed, we are more likely to get sick, but exactly why this occurs has been difficult to define, until now. The imaging showed us that stress caused immune cells to stop moving, preventing them from protecting against disease,” he explained.

“Movement is central to how immune cells can get to the right parts of the body to mount an immune response against infections or tumours, so it was surprising to see that the stress signals had such a rapid and dramatic effect on how immune cells move around.

“We also showed that it was different types of immune cells that were affected, and that it can occur in many different parts of the body.”

Professor Mueller said knowing how stress can impair immune responses may provide new avenues to overcome the negative effects of stress on immunity.

“For instance, cancer patients face increased stress that can contribute to a decreased ability of the body to fight the disease, and we might be able to use our findings to improve immune responses to those patients.”

He added that there are many reasons why the body produces these signals from the nervous system, called neurotransmitters – they control heart rate and blood pressure for instance. The team found that nerves don’t halt immune cells in all instances, only in response to significant stress.

“It’s also difficult to study what kind of stress signals could induce the immune cells to stop – is it a sudden shock? Or chronic psychological stress?” Professor Mueller said.

“The next steps in this project will be to study the mechanisms of this process. In addition, we will use the findings to test if immune responses to cancer are suppressed by sympathetic nervous system stress signals and if we can use this to boost anti-cancer responses in patients.”

This project was conducted in collaboration with Associate Professor Erica Sloan at the Monash Institute of Pharmaceutical Sciences.