A study from the Yale School of Medicine has demonstrated that a common venom found in bee stings triggers an immune response that keeps future allergic reactions to the toxin under control.

The Yale research team tested to see if longstanding antibody and immune response to bee venom could be conferred through repeated exposure to the venom. In the study, mice were injected with an allergic component of this venom, the enzyme PLA2, which triggered an allergic response and the first steps of acquired immunity to the venom. After repeated exposure to PLA2, the mice were found to be protected against severe allergic reactions. Since PLA2 is found in almost all venoms, the research suggests it may be possible to develop vaccinations against a wide range of allergic reactions, said senior author and Yale professor of immunobiology Ruslan Medzhitov.

“People have been wondering for a long time why allergy even exists,” Medzhitov said. “Why didn’t we evolve to lose this component of immunity if all it does is make us miserable? We found proof for a concept that allergy is a protective reaction, just like pain – it is unpleasant, but it is meant to be unpleasant to protect us from the greater harm.”

When PLA2 enters the body, it triggers the activation of mast cells, leading to the release of histamines and other inflammatory measures. The inflammation, itching, tearing, vomiting, sneezing and runny nose that take place during allergic reactions can be aggravating, but help expel the toxin from the body. The venom also causes an immune response through activating the antibody IgE. Repeated exposure to the venom maintains the IgE antibody and low-level allergic response in the future.

The classical view of allergies is that the response was a physiological mistake by the body, and this finding adds to a body of recent evidence shifting this opinion, said lead author and member of the Department of Immunobiology Noah Palm GRD ’11. The fact that PLA2 is shared among so many venoms shows how the body may have a limited number of mechanisms to deal with venom from a range of animals, he added.

The finding suggests new directions for understanding the connection between the immune system and allergies, said Rachel Rosenstein GRD ’12 MED ’13, lead author and associate faculty member of the Yale Medical School. She added that individual differences in how people respond to stings may depend on genetic and environmental influences on the immune system.

“Our research was done in mice, and confirming in humans would be difficult, but this gives support to the concept of venom immunotherapy and the concept that increased exposure to allergens can be protective,” she said.

About 2 million people in the United States are allergic to bee stings, causing 100 deaths a year.