In autoimmune diseases, the body’s immune system attacks organs in the body. Multiple sclerosis is the most common autoimmune disease of the central nervous system.
In MS, the immune system attacks myelin, the protective sheath that covers nerve fibers. The disease causes communication problems between your brain and the rest of your body.
Life history theory suggests that when the environment is right, the resources used by any organism are devoted to growth and reproduction. In hostile environments, resources are shifted from growth and reproduction programs to maintenance programs. Besides immunity, these maintenance traits include adaptations to energy scarcity and changes in ambient temperature.
Scientists from the University of Geneva (UNIGE) have developed this idea in a specific field of medicine: the erroneous activation of the immune system at the origin of autoimmune diseases.
They studied mice suffering from a model of multiple sclerosis. They wanted to understand how exposure to cold caused the body to divert resources from the immune system towards maintaining body heat.
Scientists placed the mice in a relatively cooler living environment – around 10 Â° C – after acclimating to the gradually decreasing environmental temperature. They discovered that exposure to cold decreases MHCII on monocytes. It also suppresses the initiation and pathogenicity of T cells through the modulation of monocytes.
Doron Merkler, professor in the Department of Pathology and Immunology and the Inflammation Research Center of the Faculty of Medicine at UNIGE and co-author of the book, said: âAfter a few days, we observed a marked improvement in the clinical severity of the disease as well as the extent of demyelination observed in the central nervous system. The animals had no difficulty in maintaining their body temperature at a normal level, but, singularly, the symptoms of locomotor impairments were considerably reduced, from the inability to walk on their hind legs to only a slight paralysis of the tail.
Exposure to cold modulates the activity of inflammatory monocytes by reducing their antigen presentation capacity. This made T cells, a type of cell that plays an essential role in autoimmunity, less activated. “
Mirko Trajkovski noted, âBy forcing the body to increase its metabolism to maintain body heat, the cold takes resources away from the immune system. This leads to a decrease in harmful immune cells and therefore improves the symptoms of the disease. “
âWhile the concept of prioritizing thermogenic over immune response protects against autoimmunity, it should be noted that exposure to cold increases susceptibility to certain infections. Thus, our work may be relevant not only for neuroinflammation, but also for other immune-mediated or infectious diseases, which warrants further investigation. “
- Martina Spiljar, Karin Steinbach et al. Exposure to cold protects against neuroinflammation through immunological reprogramming. DO I: 10.1026 / j.cmet.2021.10.002