Mast cells as a sensor: Enigmatic immune cells help us avoid harmful
allergens

Date:
July 12, 2023
Source:
German Cancer Research Center (Deutsches Krebsforschungszentrum,
DKFZ)
Summary:
The function of mast cells, which are part of the immune system,
is still a mystery. Scientists have now shown in mice: mast cells
function as a sensor that signals the animals to avoid antigens,
including harmful allergens, and thereby protect themselves from
health-threatening inflammatory reactions.


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FULL STORY ==========================================================================
The function of mast cells, which are part of the immune system, is
still a mystery. Scientists at the German Cancer Research Center (DKFZ)
have now shown in mice: mast cells function as a sensor that signals
the animals to avoid antigens, including harmful allergens, and thereby
protect themselves from health-threatening inflammatory reactions. The
findings were published in the journal Nature.

Mast cells are found primarily in tissues that separate the outside and
inside worlds of the body, such as the epithelia of the gastrointestinal
tract and lungs. Within the tissues, mast cells often reside near nerve endings. Mast cells are well known to persons suffering from allergies
because they secrete messenger substances such as histamine, which cause annoying to health- threatening allergic symptoms. These symptoms occur
when mast cells are activated by IgE class antibodies during repeated
antigen contact.

"Why mast cells and IgE exist at all has not yet been conclusively
explained," says Hans-Reimer Rodewald. The DKFZ immunologist and his team
have now been able to show for the first time in mice, in a combination of behavioral experiments and immunological studies, that mast cells act like
a sensor that helps to avoid contact with allergens No antigen avoidance without mast cells and IgE The DKFZ researchers immunized mice with
the allergen ovalbumin, a protein component of chicken egg white. They
then gave the animals the free choice of preferring either normal or
egg white-containing drinking water. Immunized animals avoided the egg white-enriched water, while their non-immunized conspecifics clearly
preferred it. A large proportion of the immunized animals avoided the
egg white-containing water already one day after immunization, some mice
even after the first sip.

However, when the scientists performed this behavioral test with mice that genetically lack mast cells, both immunized and non-immunized animals
preferred the egg white-containing water. Mice genetically unable to
produce IgE also showed no avoidance behavior. Thus, both components --
mast cells and IgE - - are responsible for antigen avoidance.

When the immunized mice had no choice because the egg white solution was instilled in them, the animals developed inflammation in the stomach and
small intestine. "The avoidance behavior mediated by mast cells apparently protects the animals from harmful immune reactions," explains Thomas Plum,
one of the first authors.

How do mast cells "talk" to the brain? An important open question for
the scientists was now: How can mast cells, as a component of the immune system, influence behavior? In what ways do immune cells "talk" to the
brain? The scientists examined a variety of biologically active substances released by mast cells. These include leukotrienes, pro- inflammatory messengers known to activate sensory nerves. If the researchers blocked leukotriene synthesis, the immunized mice no longer showed the same
consequence in avoiding egg white. Leukotrienes therefore appear to be
at least partly involved in avoidance behavior. Further immunological and neurobiological experiments are needed in the future to identify the nerve connections through which the mast cell signal is reported to the brain.

"In the intestine, lungs or skin, immune reactions against non-infectious antigens can occur as a result of so-called barrier disorders,
permeability of the tissues from the outside to the inside. In the case
of allergy, we call such antigens allergens. Whether these substances are dangerous or not, it is important for the organism to avoid their further intake in order to prevent inflammatory diseases. This is an evolutionary advantage and finally a conclusive explanation of the physiological role
of mast cells and IgE," Rodewald summarizes the results.

Whether mast cells also contribute to the avoidance of harmful antigens
in humans must be addressed in further studies.

* RELATED_TOPICS
o Health_&_Medicine
# Immune_System # Lymphoma # Stem_Cells # Brain_Tumor #
Allergy # Skin_Cancer # Nervous_System # Medical_Topics
* RELATED_TERMS
o Immune_system o Allergy o Monoclonal_antibody_therapy o
Necrosis o White_blood_cell o Antioxidant o Protein o Neuron

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========================================================================== Journal Reference:
1. Thomas Plum, Rebecca Binzberger, Robin Thiele, Fuwei Shang, Daniel
Postrach, Candice Fung, Marina Fortea, Nathalie Stakenborg, Zheng
Wang, Anke Tappe-Theodor, Tanja Poth, Duncan A. A. MacLaren,
Guy Boeckxstaens, Rohini Kuner, Claudia Pitzer, Hannah Monyer,
Cuiyan Xin, Joseph V.

Bonventre, Satoshi Tanaka, David Voehringer, Pieter Vanden Berghe,
Jessica Strid, Thorsten B. Feyerabend, Hans-Reimer Rodewald. Mast
cells link immune sensing to antigen-avoidance behaviour. Nature,
2023; DOI: 10.1038/s41586-023-06188-0 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/07/230712124624.htm

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