"Freeze to death" immune cells may save autoimmune diseases

Yesterday has officially entered the "three nines", "three nines and four nines on the ice", we are going to experience the coldest stage of winter, but it also means that spring is not far away
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All things will come back to life in spring, but unfortunately many people's allergic reactions will also be "awakened" when spring arrives
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Although there are many factors that cause allergies, including foreign matter such as dust and microorganisms, there may be some allergic diseases (autoimmune diseases) that are related to temperature, or, in other words, to the distribution of energy in the body
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In the field of evolutionary biology, "life history theory" is one of the representatives of many theories, which was first proposed in the 1950s and emphasized that all organisms face a fundamental challenge, that is, to make Balance to maximize your own interests at the moment
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For example, when the environment is favorable, resources used by the organism will be used for survival and reproduction; when the environment is harsh, resources are diverted for "maintenance" strategies, such as saving energy to resist the invasion of the harsh environment
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In autoimmunity, the body produces an energy-intensive pro-inflammatory immune response
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Such energy-demanding processes may compete with each other, and thus, the priority of a task may be the result of an energy trade-off
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This concept would be of particular interest in autoimmune diseases, where additional energy expenditure strategies may lead to milder immune responses and disease outcomes
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Therefore, the researchers hypothesized that when there is a problem with the immune system, we may be able to redirect the body's energy expenditure to treat the disease
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In a recent cover study published in Cell Metabolism, a research team led by the University of Geneva in Switzerland introduced this hypothesis to a specific field of medicine - autoimmune diseases
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By studying mouse models of multiple sclerosis, researchers have uncovered how exposure to cold temperatures prompts the body to use the immune system's resources to maintain body temperature and improve disease symptoms
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The findings pave the way for fundamental biological concepts of energy distribution
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Our body's defense mechanisms against harsh environments are energy-intensive, and when several of these mechanisms are activated, they may be limited by energy tradeoffs
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Therefore, the organism may have to allocate resources to different defense mechanisms according to its survival value
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Autoimmune diseases occur when the immune system attacks its own organs
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For example, type 1 diabetes and multiple sclerosis
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Multiple sclerosis (MS) is the most common autoimmune disease of the central nervous system, including the brain and spinal cord
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The disease is characterized by the destruction of the myelin sheath, the protective insulating layer of nerve cells that is important for the correct and rapid transmission of electrical signals
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Thus, its destruction results in disability, even paralysis, of the nervous system
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To test this hypothesis, the researchers placed a mouse model with experimental autoimmune encephalomyelitis (human multiple sclerosis) in a relatively cold environment (about 10°C) and had An acclimation period of gradually reducing the ambient temperature
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After a few days, they observed a marked improvement in the clinical severity of the animals' disease and in the degree of demyelination in the central nervous system
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In addition, their dyskinesia symptoms decreased significantly, from being unable to walk on their hind limbs to having only mild paralysis of the tail
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Let's see why this is
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It is well known that the basis of the immune response is the ability of antigen-presenting monocytes to instruct T cells how to recognize "non-self" substances that they must fight against
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In autoimmune diseases, however, "self" antigens are confused with "non-self" antigens
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The researchers found that exposure to low temperatures modulates the activity of inflammatory monocytes by reducing their antigen-presenting capacity, resulting in decreased T cell activity
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Cold temperatures force the body to increase metabolism to maintain body temperature, "taking away" some of the immune system's resources in the process, resulting in fewer immune cells that cause harmful responses, resulting in amelioration of disease symptoms
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This study also shows that the role of monocytes in the initiation of autoimmune T cells has long been underestimated
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Professor Mirko Trajkovski, Department of Cell Physiology and Metabolism and Diabetes Centre, Faculty of Medicine, University of Geneva, corresponding author of the study, said: "While the priority of thermogenesis over the immune response may protect against autoimmune diseases, it is worth noting that exposure to cold also Increased susceptibility to certain infections
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Therefore, our research work is not only related to neuroinflammation, but also to other immune-mediated diseases or infectious diseases, which requires further study
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" The researchers said that in the past few decades , the improvement of living conditions in Western countries is obvious, however, at the same time, the cases of autoimmune diseases are also increasing
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"While this increase is undoubtedly multifactorial, the fact that excess energy resources may play an important role in the development of autoimmune diseases is poorly understood," Trajkovski said
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"The team will continue their research to better understand whether the findings of this study can be used clinically
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Link to the paper: https://doi.
org/10.
1016/j.
cmet.
2021.
10.
002