Trans-generational immune priming in a social insect.

Detecting functional homology between invertebrate and vertebrate immunity is of interest in terms of understanding the dynamics and evolution of immune systems. Trans-generational effects on immunity are well known from vertebrates, but their existence in invertebrates remains controversial. Earlier work on invertebrates has interpreted increased offspring resistance to pathogens as trans-generational immune priming. However, interpretation of these earlier studies involves some caveats and thus full evidence for a direct effect of maternal immune experience on offspring immunity is still lacking in invertebrates. Here we show that induced levels of antibacterial activity are higher in the worker offspring of the bumblebee, Bombus terrestris L. when their mother queen received a corresponding immune challenge prior to colony founding. This shows trans-generational immune priming in an insect, with ramifications for the evolution of sociality.