The Drosophila Thioester containing Protein-4 participates in the induction of the cellular immune response to the pathogen Photorhabdus

The function of thioester-containing proteins (TEPs) in the immune defense of the fruit fly Drosophila melanogaster is yet mostly unexplored. Recently, we showed the involvement of TEP4 in the activation of humoral and phenoloxidase immune responses of Drosophila against the pathogenic bacteria Photorhabdus luminescens and Photorhabdus asymbiotica. Here, we investigated the participation of Tep4 in the cellular defense of Drosophila against the two pathogens. We report significantly lower numbers of live and dead plasmatocytes in the tep4 mutants compared to control flies in response to Photorhabdus infection. We also find fewer crystal cells in the control flies than in tep4 mutants upon infection with Photorhabdus. Our results further suggest that Drosophila hemocytes constitute a major source for the transcript levels of Tep4 in flies infected by Photorhabdus. Finally, we show that Tep4 participates in the phagocytic function in Drosophila adult flies. Collectively our data support the protective role for TEP4 in the cellular immune response of Drosophila against the entomopathogen Photorhabdus.