Ascidian cytotoxic cells: from zero to hero

Until four decades ago, ascidian cytotoxic cells were considered too differentiated to exert any important function in the biology of the organisms. Their unique accepted roles were related to tunic synthesis and storing nutrients (trophocytes) useful to support other processes. Things changed starting from the beginning of the eighties of the last century when it progressively became clear that they are directly involved in inflammatory reactions. In the last decade, it was ascertained that these cells, once neglected, deeply influence ascidian biology, as they are the main source of cytokines modulating the activity of immunocytes, and of the majority of the complement components that assure correct immune responses. Moreover, they can also produce and release antimicrobial peptides that protect the organism from infections.