The scientists then carried out a more detailed analysis of the molecules secreted by platelets, which may be behind the process. Molecules secreted by platelets may be behind the process Conversely, increasing the platelet count in the blood resulted in a much worse allergic reaction. To confirm their function, the scientists eliminated the platelets from the blood, which led to a reduction in symptoms. Injecting these mice with human IgG antibodies triggered an anaphylactic reaction, characterized by a drop in body temperature and leading to a significant reduction in the circulating platelet count that lasted for several hours after the shock, suggesting that platelets might play a role in the allergic reaction.
To study the role of platelets in anaphylaxis, the scientists used transgenic mice expressing human receptors for IgG antibodies, since mice do not have these receptors on their platelets. The role of blood platelets in anaphylaxis In this study, scientists from the Antibodies in Therapy and Pathology Unit (Institut Pasteur/Inserm U1222) revealed that platelets, whose best-known function is to stop bleeding when a blood vessel becomes damaged, play a key role in IgG-dependent anaphylactic reactions. But animal studies revealed that an alternative pathway depending on IgG-type antibodies exists. While it was already known that IgE antibodies can trigger these allergic reactions, scientists from the Institut Pasteur, Inserm, the CNRS and EFS Grand Est recently demonstrated that IgG antibodies play an active role in the severity of anaphylactic shock by unexpectedly activating blood platelets.Īllergies are generally associated with the presence of IgE antibodies, which are responsible for activating specific cells in the immune system that secrete histamine, giving rise to clinical signs. The production of antibodies against this antigen (or allergen) allows the formation of antibody-antigen complexes that trigger a massive secretion of potent mediators, resulting in organ failure, which may lead to a state of shock and possibly death.
The most severe allergic reaction, anaphylaxis (or anaphylactic shock), is the result of an inappropriate immune reaction following the introduction of a usually harmless antigen into the body.
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