Researchers at the Champalimaud Centre for the Unknown and the Instituto de Medicina Molecular, in Lisbon, have discovered that neurons located at mucosal tissues can immediately detect an infection in the organism, promptly producing a substance that acts as an "adrenaline rush" for immune cells. As a result, the immune cells can get ready quickly to fight infection and repair damage. These results can be seen in Nature today.
In this new study, researchers focused on ILC2s, a type of innate lymphoid cell. ILC2s produce substances that are essential to immune responses against parasites, such as worms. "These cells are normally abundant at barrier sites, such as the gut, lungs and skin", which serve as physical fortresses to the body," explains Henrique Veiga-Fernandes, Ph.D, principal investigator of the study. The team has now shown that these immune cells would not be able to develop their protective actions against infections without establishing a "dialog" with neurons residing at those sites.
The study brings "two big novelties", says Veiga-Fernandes. The first, he explained, "is that neurons define the immune cells' function. Nobody could have imagined that the nervous system coordinates, commands, and controls the immune response throughout the whole organism." Second, he added, "it's one of the fastest and most powerful immune reactions we have ever seen". Comparatively, the newly discovered neuronal stimulus induces an immune response in a few minutes, while the immune response following vaccination typically takes several weeks to mount.
In addition, the authors also found that ILC2s have receptors to a neuronal messenger called neuromedin U (NMU), which is reported to only be produced in high levels by neurons. To confirm the role of NMU, researchers had two cohorts of mice, one group that was "normal" and the other whose ILC2s had been stripped of NMU receptors. They found that after infection of Nippostrongylus brasiliensis, only the "normal" group was able to fight the infection.
The researchers also showed that neurons are able to detect the products secreted by parasites that infect the organism, which triggered them to massively produce NMU to act on ILC2s and generate an immune response.
The results provide hope for a way to create a quick immune response. However, "we are still very far from understanding how we could safely use this neuro-immunological 'bomb'; for now, we are at the fundamental research level," Veiga-Fernandes reports.
Image: Innate lymphocytes (in green) surround the gut (in red). Image courtesy of Henrique Veiga-Fernandes.