BioAcyl Corp

Notable example of trained immunity

We find that populations adapted to high levels of parasitism evolved two phenotypes that likely explain their higher resistance. Firstly, they produce more hemocytes in homeostasis, which leads to a faster increase in circulating hemocytes in early time points of infection. Secondly, they produce lamellocytes more rapidly upon infection, likely largely due to the constitutive production of immature lamellocytes. Furthermore, cytotoxic molecules could be more readily available as there is an increase in the constitutive expression of PPO3 in populations adapted to high rates of parasitism. PPO3 encodes an intracellular prophenoloxidase produced by lamellocytes that, when activated, is responsible for the capsule melanization (Dudzic et al., 2015). We conclude that the constitutive activation of the cellular immune response likely explains the greatly increased resistance of populations adapted to high rates of parasitism.