Properties of cell subpopulations of starfish axial organ: in vitro effect of pokeweed mitogen and evidence of lymphokine-like substances.

The in vitro effects of pokeweed mitogen (PWM) on axial organ (AO) cells of the echinoderm starfish Asteria rubens have been studied. PWM stimulates 3H-thymidine incorporation by the whole population of AO cells (index of stimulation 4-5). On the basis of surface adherence to nylon wool the AO cell population can be fractionated into adherent and non-adherent subpopulations. PWM strongly stimulates the non-adherent cells (index 14) but not the adherent cells (index 1.2-1.8). Specific soluble mediators obtained from stimulated non-adherent cells were able to stimulate the whole AO cell population but not the fractionated adherent or non-adherent cells.