Time to be selfish when infection strikes
The EU-funded IMMUNE ENERGY (Extracellular adenosine role in energetic metabolism during immune response) project trained their researchers to learn techniques of infection in the fruit fly Drosophila. Fully equipped, the team then went on to study the role of extracellular adenosine in energy regulation during immune response. Three models showed different outcomes of manipulating energy on immune response – Streptococcus pneumoniae and intracellular pathogen Listeria monocytogenes as well as a parasitoid wasp infection of a fruit fly larva where the egg is laid in the larva's body. They all demonstrated that adenosine is needed and is produced by immune cells on infection. This molecule acts a mediator of a metabolic switch that channels energy from the rest of the body to the immune system. Without adenosine there is a markedly reduced response. The notion of the selfish immune system, which places it at the top of the hierarchy for energy is apparently not so simplistic. Although blocking adenosine signalling decreases resistance and increasing adenosine magnifies response against Streptococcus, there are exceptions. Enhancing adenosine effects is counterproductive during chronic Listeria infection. Interestingly, tight regulation works against a long lifespan and decreasing adenosine under non-stressful conditions extends lifetime. These results are pending publication. The complex host-pathogen interactions and adenosine-mediated role of energy regulation in these interactions were selected as a platform presentation at the prestigious Annual Drosophila Research Conference in 2014. Visual media from the project can be seen on YouTube. This gruesome account of the infection of a Drosophila larva by a parasitoid wasp followed by the two responses of the immune system is very interesting. The laboratory web pages give an illustrated account of IMMUNE ENERGY work. Extending the idea of the selfish immune system may explain modern day autoimmune pathologies such as diabetes and obesity. Advancing knowledge on this aspect of immunity may have far-reaching implications and a profound impact on public health generally. The Drosphila model developed by the IMMUNE ENERGY team may be enhanced to discover mechanisms behind, for example, the metabolic syndrome.
Keywords
Infection, immune response, Drosophila, adenosine, selfish immune system
