Does the Immune System Age?

It is fairly well known that increased activation of the innate immune system is a common feature of aging animals. This paper by some friends of ours looks to determine whether the increase in the activation of the immune system in flies is a functional one, or just a by product of aging.

This experiment is actually very simple, luckily for us, a short one! This paper found that while in a non-infected state, the antimicrobial peptides (the end product of immune system activation) older flies express more than younger flies, which was expected. The interesting part is when flies of varying age were infected, it as found that older flies, while having a higher basal level of immune activation, could not induce the immune system to as high an extent as young flies in response to infection. Moreover, it took older flies longer to turn off their immune response than it did for young flies. The authors hypothesize that this decreased capacity to induce the immune system in older flies leads to persistent infection, which could be why we see the immune system always turned on a little bit in old flies.

Well, believe it or not, that's all there is to the paper. I told you it was short!