The Italian researchers behind this current work previously analyzed an infection present in bees. But the concerns being raised about insecticides motivated them to look into whether there might be a connection between the two. Rather than focusing on bee mortality, they decided to look at the pathways that mediate immune responses in insects.
Bees lack that adaptive immune system that generates pathogen-specific antibodies and T cells in mammals. But they share an innate immune system, which is able to generally recognize infectious agents like bacteria. In fact, this innate immune system is evolutionarily ancient, as the same genes are used to control the response in animals as distantly related as bees and humans.
Previous toxicology work in mammals indicated that a specific class of insecticides, the neonicotinoids, could influence the activity of genes involved in the innate immune system. These genes were activated by the presence of neonicotinoids, and they shut down a key regulator of the innate immune system (a protein called NF-κb). Thus, the more of these insecticides, the less effective the innate immune system is likely to be—at least in mammals.
The researchers started by showing that the same is true in insects. Initially, they worked with everyone's favorite fruit fly, Drosophila, showing that the equivalent genes responded in the same ways in the flies. They then showed that the innate immune response isn't activated when these same flies are exposed to an infection. A different class of insecticide (an organophosphate) had a much weaker effect on the fly's innate immunity. With the molecular activity well characterized, they went on to demonstrate that the same effects could be seen in bees.
http://arstechnica.com/science/2013/10/an-insecticide-infection-connection-in-bee-colony-collapses/
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