Characterization of Ascidian Plasma Growth Factors Promoting the Proliferation of Mouse Thymocytes

The plasma of a solitaly ascidian, Halocynthia roretzi, stimulates the proliferation of mouse thymocytes in the presence of a mitogen, phytohemagglutinin P (PHA-P). Eight factors capable of stimulating the proliferation of mouse thymocytes were isolated from H. roretzi plasma by procedures including hydrophobic chromatography, gel filtration, and anion-exchange chromatography. Four active fractions with molecular weights of 100–110 K, 75–90 K, 10–30 K, and 5–6 K were first separated by gel filtration. Each of these fractions was then separated into two fractions with different ionic properties by anion-exchange chromatography. The eight factors thus obtained have different heat stabilities, heparin-binding abilities, and PHA-P sensitivities.