Primitive cytokines and cytokine receptors in invertebrates: the sea star Asterias rubens as a model of study.

It has been previously demonstrated that the sea star axial organ is a primitive immune organ. Phagocytic, lymphoid-like cells have been characterized with properties similar to those of vertebrates. There is also evidence for an invertebrate cytokine network because IL-1 and TNF-like activities are clearly demonstrable. In addition, the authors have previously described preliminary evidence for IL-2-like activity in the sea star. In the present report, the authors obtained evidence for the presence of IL-1- and IL-2-like molecules on axial organ cells. More interestingly, the results suggested that sea star cells express structures similar to human receptors for IL-1, IL-2, IL-6 and IFN-gamma.