PROLIFERATION OF UNDIFFERENTIATED BLOOD-CELLS FROM THE SOLITARY ASCIDIAN, CIONA-INTESTINALIS IN-VITRO

The proliferative responses of the cytotoxic blood cell population of the solitary ascidian, Ciona intestinalis, were investigated by autora diography and tritiated thymidine (H-3-TdR) incorporation following tr eatment with mitogens or coculture with allogeneic cells in vitro. A s mall number of mitotic figures were seen in untreated circulating bloo d cells and pulse labelling with H-3-TdR showed that only the undiffer entiated ''lymphocyte-like'' cells within the enriched cytotoxic cell population undergo spontaneous cell division and DNA synthesis in the circulation, Treatment of the cells, cultured for 4 days, with concana valin A (con A), phytohaemagglutinin-B (PHA-B) or lipopolysaccharide ( LPS) produced significantly increased H-3-TdR incorporation, although there were differences in the sensitivity of the cells to mitogen conc entration. Significantly enhanced proliferation was also observed foll owing incubation with mitomycin C-treated cells from allogeneic indivi duals, These results show that the cytotoxic blood cell population of C. intestinalis is capable of mitogen-induced proliferation as well as mixed lymphocyte-type responses and therefore shares some proliferati ve characteristics with vertebrate lymphocytes.