Researchers at Duke University School of Medicine have discovered that the nervous system plays a crucial role in the anaphylactic response, particularly the drop in body temperature, which has long been attributed to blood vessel dilation and leakage. This response occurs in up to 5% of people in the U.S. annually in response to food allergies or bites from insects or venomous animals. The researchers found that the sensory nerves involved in thermal regulation, especially those that sense high environmental temperatures, send a false signal to the brain during anaphylaxis that the body is exposed to high temperatures even though it is not. This causes a rapid drop in body temperature as well as blood pressure. The researchers tracked the sequence of events when allergens activate mast cells, which are immune cells that trigger the chemical reactions leading to swelling, difficulty breathing, itchiness, low blood pressure, and hypothermia. They found that one of the chemicals mast cells unleash when they are activated is an enzyme that interacts with sensory neurons, particularly those involved in the body’s thermoregulatory neural network. The study could point to new targets for therapies to prevent or treat anaphylactic shock.
Key Role of Nervous System Identified in Severe Allergic Shock
Anaphylaxis, a severe allergic reaction, is characterized by an abrupt drop in blood pressure and body temperature that can cause people to faint and potentially die if left untreated. This response has long been attributed to blood vessel dilation and leakage, but a recent study conducted on mice by researchers at Duke University School of Medicine suggests that another mechanism – the nervous system – is also responsible for this response, particularly the drop in body temperature. The study, which was published in the journal Science Immunology, may lead to new therapies for preventing or treating anaphylactic shock, which affects up to 5% of people in the U.S. annually in response to food allergies or bites from insects or venomous animals.
According to senior author Soman Abraham, PhD, professor in the departments of Pathology, Immunology, and Molecular Genetics and Microbiology at Duke University School of Medicine, “This finding for the first time identifies the nervous system as a key player in the anaphylactic response.” He explained that the sensory nerves involved in thermal regulation, especially those that sense high environmental temperatures, send a false signal to the brain during anaphylaxis that the body is exposed to high temperatures even though it is not. This causes a rapid drop in body temperature as well as blood pressure.
The researchers tracked the sequence of events when allergens activate mast cells, which are immune cells that trigger the chemical reactions leading to swelling, difficulty breathing, itchiness, low blood pressure, and hypothermia. They found that one of the chemicals mast cells unleash when they are activated is an enzyme that interacts with sensory neurons, particularly those involved in the body’s thermoregulatory neural network.
When stimulated as part of an allergic reaction, this neural network gets the signal to immediately shut down the body’s heat generators in the brown fat tissue, causing hypothermia. The activation of this network also causes a sudden drop in blood pressure.
The researchers validated their findings by showing that depriving mice of the specific mast cell enzyme protected them against hypothermia, whereas directly activating the heat-sensing neurons in mice induced anaphylactic reactions such as hypothermia and hypotension.
In conclusion, this study highlights the importance of the nervous system in the anaphylactic response, specifically in the drop in body temperature. It opens up new avenues for therapies to prevent or treat anaphylactic shock and could lead to significant improvements in the management of this potentially life-threatening condition.
PhD candidate Chunjing “Evangeline” Bao, from Duke University School of Medicine, states that the nervous system is a crucial player in the anaphylactic response, presenting potential targets for therapy and prevention. Bao also notes that this finding could be important for other conditions, such as septic shock.
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