Fig. 5.

Working model of innate immune memory in primed A. gambiae mosquitoes. Ookinete invasion allows direct contact between the gut microbiota and midgut epithelial cells by disrupting the peritrophic matrix, and triggers the systemic release of PGE₂ by the midgut. High levels of PGE₂ result in higher expression of DBLOX in the abdominal wall. DBLOX is highly expressed in oenocytes, and the numbers of oenocyte clusters and cells per segment increase constitutively in primed mosquitoes. This increase in oenocytes requires the activity of the HAT AgTip60. Silencing either DBLOX or AgTip60 disrupts the synthesis of the HDF and immune priming. Constitutively high levels of HDF promote hemocyte differentiation to granulocytes and enhance the immune response to subsequent infections.