Cell cooperation among immunocytes of the compound ascidian Botryllus schlosseri

Two different immunocyte types are present in the blood of the colonial ascidian Botryllus schlosseri: phagocytes and morula cells (MC). The latter are cytotoxic cells, involved in the inflammatory reaction which occurs when genetically incompatible colonies contact each other. Upon the recognition of non-self molecules, MC release of the proenzyme prophenoloxidase, readily converted to active phenoloxidase which is directly responsible for the induction of cytotoxicity observed along the contacting colonial borders in the forms of a series of pigmented, necrotic spots. We have recently demonstrated that MC respond to the recognition of non-self molecules from the microbial surface through the synthesis of molecules recognised by antibodies raised against mammalian IL-1-a and TNF-a.Here, we demonstrate that MC synthesise the above-reported molecules as a consequence of the recognition of both bacteria and non-self factors from incompatible blood. The positivity is located in the cytosol. In addition, since lysates of MC, previously exposed to bacteria, have been claimed to increase phagocytosis in the solitary ascidian Ciona intestinalis, we investigated whether anti-IL-1-a- and anti-TNF-a-antibodies and recombinant IL-1-a and TNF-a can influence the activity of phagocytes. Data obtained clearly show a significant (p < 0.01) decrease of yeast phagocytosis in the presence (1 μg/ml) of anti-cytokine antibodies whereas, a significant (p<0.01) increase is reported when phagocytosis occurred in the presence (10 ng/ml) of the recombinant cytokines. The results support the hypothesis of a role of IL-1-a- and TNF-a- immunopositive molecules in communication among immunocytes.