By studying mice with a model of multiple sclerosis, scientists succeeded in deciphering how exposure to cold pushed them to divert resources from the immune system towards maintaining body heat. During cold the immune system decreased its harmful activity, which considerably attenuated the course of the disease. These results pave the way for a fundamental biological concept on the allocation of energy resources.    

The researchers at the University of Geneva wanted to know if they could divert the energy expended by the body when the immune system goes awry. To test their theory, the scientists placed mice with experimental autoimmune encephalomyelitis, a model of human MS, in a relatively colder living environment — about 10°C — following an acclimatization period of gradually decreasing the environmental temperature. After a few days, they observed a clear improvement in the clinical severity of the disease as well as in the extent of demyelination observed in the central nervous system. The animals did not have any difficulty in maintaining their body temperature at a normal level, but, singularly, the symptoms of locomotor impairments dramatically decreased, from not being able to walk on their hind paws to only a slight paralysis of the tail.

The immune response is based, among other things, on the ability of so-called antigen-presenting monocytes to instruct T cells how to recognize the “nonself” elements that must be fought. In autoimmune diseases, however, the antigens of the “self” are confused with those of the “nonself.” Researchers showed that cold modulates the activity of inflammatory monocytes by decreasing their antigen-presenting capacity, which rendered the T cells less activated. By forcing the body to increase its metabolism to maintain body heat, 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.

Results of mouse model studies sometimes do not translate to humans. However, the researchers will now pursue their research to better understand whether their discovery could be developed in clinical applications.

The findings were published in the journal Cell Metabolism.