The Diverse Transformer (Trf) Protein Family in the Sea Urchin Paracentrotus lividus Acts through a Collaboration between Cellular and Humoral Immune Effector Arms

Sea urchins are long-living marine invertebrates with a complex innate immune system, which includes expanded families of receptors. A central gene family in sea encodes the Transformer (Trf) proteins. The Trf has been studied mainly purple urchin Strongylocentrotus purpuratus. Here, we explore this protein Mediterranean Paracentrotus lividus. PlTrf genes and predicted proteins highly diverse show typical size range structure. Coelomocytes cell-free coelomic fluid from P. lividus contain different repertoires shared subset, that bind specifically to E. coli. Using FACS, identified five coelomocyte sub-populations cell surface expression. relative abundance PlTrf-positive cells increases sharply following challenge coli, but not LPS or pathogen, Vibrio penaeicida. Phagocytosis coli by phagocytes is mediated through inhibited blocking activity anti-SpTrf antibodies. Together, our results suggest collaboration between cellular humoral PlTrf-mediated effector arms specific response pathogens.