Anaphylaxis is a severe allergic reaction that can cause people to faint and potentially die if left untreated. Duke Health researchers have found that an abrupt drop in blood pressure and body temperature is a key feature of anaphylaxis, and the nervous system plays an additional role in causing body temperature to drop. This response has long been attributed to blood vessel dilation and leakage. The study could point to new targets for therapies to prevent or treat anaphylactic shock, which 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 also discovered that sensory nerves involved in thermal regulation, notably those involved in the body’s thermoregulatory neural network, send the brain a false signal during anaphylaxis that the body is exposed to high temperatures even though it is not the case. This causes a rapid drop in body temperature as well as blood pressure. Mast cells, the immune cells that trigger the chemical reactions leading to swelling, difficulty breathing, itchiness, low blood pressure, and hypothermia, unleash an enzyme that interacts with sensory neurons, leading to the body’s heat generators shutting down, causing hypothermia.
Key Feature of Severe Allergic Reaction: Abrupt Drop in Blood Pressure and Body Temperature
Researchers from Duke Health have discovered a crucial feature of anaphylaxis, a severe allergic reaction that can cause people to faint and potentially die if left untreated. The key characteristic is an abrupt drop in blood pressure and body temperature. This response has previously been attributed to blood vessel dilation and leakage; however, the Duke Health study found that the nervous system plays an additional role in causing body temperature to drop.
The findings, published in the journal Science Immunology, could lead to the development of new therapies for preventing or treating anaphylactic shock, which affects up to 5% of people in the US annually in response to food allergies, insect bites, or venomous animals.
According to senior author Soman Abraham, Ph.D., 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 the nerves that sense high environmental temperatures – send the brain a false signal during anaphylaxis that the body is exposed to high temperatures even though it is not the case. This causes a rapid drop in body temperature as well as blood pressure.”
The study’s lead author, Chunjing “Evangeline” Bao, a Ph.D. candidate in Abraham’s lab at Duke, tracked the sequence of events when allergens activate mast cells, the immune cells that trigger the chemical reactions leading to swelling, difficulty breathing, itchiness, low blood pressure, and hypothermia. The researchers found that one of the chemicals mast cells unleash when they are activated is an enzyme that interacts with sensory neurons, notably 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, Duke Health researchers have discovered that an abrupt drop in blood pressure and body temperature is a key feature of anaphylaxis, and the nervous system plays an additional role in causing body temperature to drop. The findings could lead to the development of new therapies for preventing or treating anaphylactic shock.
Nervous System a Key Player in Allergic Reaction
The Duke Health researchers’ discovery that the nervous system is a key player in anaphylactic response may lead to new prevention or therapy targets. Lead author Chunjing “Evangeline” Bao explained that this finding could also have implications for other conditions, including septic shock. The researchers are currently studying these possibilities.
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