All organisms age. One prominent hypothesis suggests that infections experienced early in life accelerate ageing. In collaboration with Jens Rolff, I tested this idea in mealworm beetles (Tenebrio molitor). We found that young beetles injected with bacterial cell components mounted an immune response that damaged their vital organs – Malpighian tubules, equivalent to kidneys – and resulted in faster ageing. Experimental down-regulation of phenoloxidase (a key component of the immune response) via RNAi allowed beetles to live longer. Similarly, older beetles infected with a live pathogen also lived longer if their immune response was suppressed. Thus, inflammation induced by immune responses may generally accelerate ageing in various contexts. These results suggest that natural selection is nearly blind to immune self-harm because its effects are felt later in life, after peak reproduction. Similar mechanisms may operate in other organisms, as ageing is a feature of most multi-cellular organisms including humans.
Read the early online version of the paper here.