Uncovering the evolutionary history of innate immunity: the simple metazoan Hydra uses epithelial cells for host defence.

Bosch TC, Augustin R, Anton-Erxleben F, Fraune S, Hemmrich G, Zill H, Rosenstiel P, Jacobs G, Schreiber S, Leippe M, Stanisak M. Uncovering the evolutionary history of innate immunity: the simple metazoan Hydra uses epithelial cells for host defence. Developmental & Comparative Immunology. 2009 Apr 1;33(4):559-69. https://doi.org/10.1016/j.dci.2008.10.004