A sudden drop in blood pressure and body temperature is a key feature of a severe allergic reaction known as anaphylaxis, causing people to faint and, if untreated, potentially die. This response has long been attributed to blood vessel dilation and leakage. However, Duke Health researchers found in a mouse study that this response, specifically a drop in body temperature, requires an additional mechanism — the nervous system.
The findings, published in the journal Science Immunology, suggest the study may point to new targets for therapies to prevent or treat anaphylactic shock, which occurs in 5 percent of people in the US annually in response to food allergies or bites from insects or venomous animals. ,
“This finding for the first time identifies the nervous system as a major player in the anaphylactic response,” said senior author Soman Abraham, professor in the Department of Pathology, Immunology and Molecular Genetics and Microbiology at Duke University School of Medicine. Of medicine “Sensory nerves involved in thermoregulation — particularly those nerves that sense high environmental temperatures — send a false signal to the brain during anaphylaxis that the body is exposed to high temperatures, even when it is not,” Abrahams said. .
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“This causes a rapid drop in body temperature as well as blood pressure.” Abraham and colleagues, including first author Chunjing “Evangeline” Bao, a Ph.D. candidate in Abraham’s lab at Duke tracked the sequence of events when allergens activate mast cells — immune cells that trigger chemical reactions leading to inflammation, difficulty breathing, itching, low blood pressure and hypothermia.
The researchers found that one of the chemicals mast cells make when activated is an enzyme that interacts with sensory neurons, specifically those involved in the body’s thermoregulatory neural network. When stimulated as part of an allergic response, this neural network is signaled to immediately shut down the body’s heat generators in brown adipose 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 specific mast cell enzymes protected them from hypothermia, while directly activating heat-sensing neurons in the mice induced anaphylactic reactions such as hypothermia and hypotension.
“By demonstrating that the nervous system is a key player — not just immune cells — we now have potential targets for prevention or treatment,” Bao said. “This finding may also be important for other conditions, including septic shock, and we are doing those studies.”