Evidence for the production of an interleukin-like protein by Asterias rubens (axial organ cells) in mixed leukocyte cultures.

Cells from the axial organ of the sea star may be separated into two subpopulations, depending on adherence to nylon wool. The non-adherent cells are morphologically and physiologically similar to Th. lymphocytes and produce an MLR-like reaction in a xenogeneic system involving two different species of sea stars. On the second day of such a MLC, these cells released molecules which were probably glycoproteins and which produced a mitogenic effect on all the axial organ cells. No effect occurred when the supernatant was tested on adherent or non-adherent cells separately, suggesting that a cellular cooperation is necessary in order to produce the response. These soluble mediators produced by T-like cells with a mitogenic effect on lymphocyte-like cells resemble the interleukin proteins produced by vertebrate leukocytes.