The Trade-off Between Pathogen Resistence and Longevity

To date very little has been done to adress whether activation of the innate immune system has any effect on fitness or longevity. In a study by Libert et al., the innate immune response was consitutively activated and it was found that although there was a higher pathogen resistence in these flies they were short lived.

It was first found that the overexpression of a peptido-glycan recognition protein, PGRP, which is the first molecule in both the Imd and Toll pathways, was enough to consitutively turn on the immune response. This conferred a wide range of resistence to bacteria and fungi. It was also found, using mutants, that this resistence was dependent on the nuclear transcription factor Relish.

The next part of the experiment examined short term trade-offs to consitutive activation of the immune system in behavious such as climbing activity, fecundity and heat shock tolerance. None of these characteristics were affected in the short term. However, it was found that chronic activation, which is similar to the chronic imflammation state in elderly mammals, reduces lifespan. According to the authors, their data are consistent with the presence of a cost for persistent enhanced immunity, and more over indicate a link between immune system signaling and genes that influence longevity.

As I have found the more I read, much of the scientific discoveries, such as this one, are not surprising given even the littles amount of thought. However, it is impossible to move forward and get to the really cool stuff until basic research such as this is completed.